Kostas A. Belibassakis

Professor

School of Naval Architecture & Marine Engineering National Technical University of Athens

CURRICULUM VITAE

Athens, August 2017

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CURRICULUM VITAE

PERSONAL DATA

Name: Kostas A. Belibassakis Professor, School of Naval Architecture and Marine Engineering, National Technical University of Athens

Address: Ship & Marine Hydrodyamics Laboratory 9 Heroon Polytechniou, Zografos, 15780, Athens

Tel. (+30) 210-7721061, (+30) 210-7721138 Fax (+30) 210-7721397

Email: kbel@fluid.mech.ntua.gr Web page: http://arion.naval.ntua.gr/~kbel/ EDUCATION: 1986 Diploma Naval Architect & Marine Engineer, National Technical University of Athens 1992 Doctor of Engineering, Dept. Naval Architecture and Marine Engineering,

National Technical University of Athens (NAME-NTUA)

ACADEMIC POSITIONS: School of Naval Architecture and Marine Engineering, NTUA: Assoc.Professor (2011-2017), with research

subject “Wave phenomena in ship and marine hydrodynamics. Hydroacoustics” Dept of Naval Architecture, Technological Educational Institute of Athens: Assist.Professor (2000-2002),

Associate Professor (2003-2007), Professor (2008-2010) with research subject “Ship theory” School of Naval Architecture and Marine Engineering, NTUA: Adjunct Professor (1996-97 and 1999-2000)

TEACHING: as Adjunct Professor at NAME-NTUA contributed in teaching of the following courses: ΕΜΠ 1996-1997: “Fundamental Principles of Ship and Marine Hydrodynamics” ΕΜΠ 1996-1997: “Water waves and acoustic waves in the sea environment” ΕΜΠ 1999-2000: “Ship Hydrodynamics”

as Professor at Dept of Naval Architecture, Technological Educational Institute of Athens ΤΕΙ-Α 1999-2009: “Ship theory (ship hydrostatics & stability, ship hydrodynamics)”

also contributed in teaching of the following graduate courses: Univ.Ioannina: “Physical, mechanical and chemical processes in materials, erosion and phase

transformations”, Interdepartmental Postgraduate Program in Chemistry and materials technology

NTUA 1999-2009: “Wave phenomena in the sea environment”, Interdepartmental Postgraduate Program Marine Technology and Science

NTUA 2005-2009: “Waveguides in the sea and coastal environment and applications”, Interdepartmental Postgraduate Program Mathematical modelling in modern technology and finance

as Associate Prof. at the School of Naval Architecture and Marine Engineering NTUA 2011-2016: “Fundamental principles of ship and marine hydrodynamics”, “Ship Dynamics”,

undergraduate courses, School of Naval Architecture and Marine Engineering NTUA 2011-2016: “Wave phenomena in the sea environment”, and “Non-linear waves”,

Interdepartmental Postgraduate Program Marine Technology and Science NTUA 2015-2016: “Ship and marine hydrodynamics”, Interdepartmental Postgraduate Program Marine

Technology and Science NTUA 2011-2016: “Waveguides in the sea and coastal environment and applications”, Interdepart.

Postgraduate Program Mathematical modelling in modern technology and finance NTUA 2015-2016: “Computational methods in hydrodynamics”, Interdepartmental Postgraduate

Program Computational Mechanics Summer 2015: participation to summer school «Wave propagation in complex media», organized by

ESPCI, CNRS, Cargèse, Corsica, August 2015.

LECTURE NOTES G.A.Athanassoulis and K.A.Belibassakis, 2008, “Wave phenomena in te sea environment”', Lecture

Notes, School of Naval Architecture and Marine Engineering, NTUA (in Greek). G.A.Athanassoulis and K.A.Belibassakis, 2012, “Ship Dynamics”, Lecture Notes, School of Naval

Architecture and Marine Engineering, NTUA (in Greek). K.A.Belibassakis, 2003, “Ship Theory”, Lecture Notes, Dept. Architecture and Marine Engineering,

Technological Educational Institute of Athens (in Greek).

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PARTICIPATION IN PHD AND DIPLOMA THESIS COMMITTEES

Supervising PhD candidates at NAME-NTUA Filippas Evangelos (start date April 2013): “Hydrodynamic analysis of biomimetic fish propulsion

systems for augmenting ship propulsion in waves” Karathanassi Flora (start date May 2014): “Stochastic modelling of linear and directional wind and wave

data with application to wave energy and beach erosion in marine and coastal environment”

Karperaki Angelina (start date December 2014): “Hydroelastic interaction of waves with large floating bodies in inhomogeneous sea environment”

Advising member of PhD Committees Papoutsellis Christos: “Non linear water waves in inhomogeneous sea environment: Theoretical and

numerical study using variational methods” (supervisor Prof. G.A.Athanassoulis NAME-NTUA, final examination stage)

Kapelonis Aris: “Stochastic propagation and scattering of sea waves” (supervisor Prof. G.A.Athanassoulis, finalisation stage)

Anastopoulos Panagiotis: “Development of mathematical model for random wave groups with application to dynamic ship stability” (supervisor Prof. Kostas Spyrou NAME-NTUA)

Tsallis Christos: “Extreme value analysis and statistical modeling of environmental data” (supervisor Professor George Kallos, University of Athens)

Kazakis Ioannis “Development of advanced numerical models for coastal hydro-morphodynamics” (supervisor Professor Theofanis Karambas, Aristotle University of Thessaloniki)

Laffitte El. “Water wave propagation above a vertically sheared current and a variable bathymetry” (supervised by Prof. V. Rey & J.Touboul, University of Toulon France).

Supervising Diploma theses Filippas Ε., 2013, “A boundary element method for the hydrodynamic analysis of flapping-foil thrusters

operating beneath the free surface and in waves”, NAME-NTUA. Papageoriou-Stamatis Ι. 2013 “A comparison of methods for predicting the wave added resistance of

slow steaming ships”, NAME-NTUA and TUDenmark (in the framework of Erasmus program). Kazakis I., 2014 “Numerical modelling of wave propagation in coastal regions by using DHI MIKE21

model”, Postgraduate Program Marine Technology and Science NTUA. Tsonis Sp., 2015, “Propagation of water waves from moving pressure distributions in variable

bathymetry regions and shallow water conditions by means of Boussinesq models”, Postgraduate Program Marine Technology and Science NTUA.

Kallikourdis G., 2016 “Study of Boussinesq models for the propagation of water waves in variable bathymetry regions and shallow water conditions” Postgraduate Program Mathematical modelling in modern technology and finance.

Kyriakis A. 2016, “Wave propagation in sea acoustic waveguide in the presence of localized scatterers”, Postgraduate Program Marine Technology and Science NTUA.

In progress

Priovolos, Α., “Hydroelastic effects in flapping thruster as biommetic propulsion systems”, NAME-NTUA

Lambrinidis, Ν. “Optimization of ship routing using weather data and focusing on propulsion energy

efficiency”, NAME-NTUA.

Thermos L., “Hydrodynamic analysis of floating bodies in variable bathymetry regions by Boundary

Element Methods”, NAME-NTUA. Telonis Angelos, “Analysis of elecromagnetic waveguides by Boundary Element Methods”, Postgraduate

Program Marine Technology and Science NTUA.

PARTICIPATION IN FINAL EXAMINATION COMMITTES Participation in a number of final PhD examination committees of Schools of NTUA (NAME, Mechanical

Engineering, Civil Engineering) Participation, as external member, in the following examination committes:

Touboul J.2014, “Etude d'évènements extrêmes liés à l'action d'ondes de gravité en milieu océanique”, Habilitation thesis, Univ.of Toulon.

Charland J. 2014 , “Modélisation de la propagation de la houle en présence d'un courant inhomogène et au dessus d'une topographie variable” (PhD thesis, supervised by V.Rey), Univ.of Toulon.

Bockmann E. 2015 “Wave propulsion of ships” (PhD thesis supervised by Sverre Steen), NTNU. Charrarye F. 2015 “Modelisation de fermes de systemes houlomoteurs: effets d’interactions entre

systemes a l’echelle de la ferme et impact sur le climat de vagues a l’echelle regionale” (PhD supervised by M.Benoit), Paris Est.

Raoult Cecile, 2016 “Nonlinear and dispersive numerical modelling of nearshore waves” (PhD supervised by M.Benoit), Paris Est.

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PARTICIPATION IN RESEARCH PROJECTS: 30-year participation in research projects funded by EU, Greek national resources (Ministry of Education, Greek Secretariat for Research and Technology (GSRT), Public & Private Sector, etc) as follows: Program for support of young researchers (GSRT PENED 1986-88, 95-96), Program for development of industrial research (GSRT-PAVE 1994-95), Bilateral Collaboration between Greece-Bulgaria (GSRT 88-90), Greece-Poland (2000-03, 2005-08), Greece-France (2003-05), EPETII-EKVAN (GSRT 1996-97), NTUA Basic Research (1999-00), EU projects: MOPIT (92-93), JOULE (96-98), MAST-III (97-00), WEU-EUCLID (1999-03), EU-IST (01-04), EU-ENVIRONMENT (2002-05), EU-GROWTH (2001-03), Operational Programme for Education and Initial Vocational Training EPEAEK-II (2003-08), ΕΠΕΑΕΚ II-Archimedes (2003-07), National Strategic Reference Framework (NSRF 2007-2013) - Program ARHIMEDES-III (2012-2015), National Strategic Reference Framework (NSRF 2007-2013) - Research Funding Program THALES (2012-2015), EU-FP7 (Marina platform, Exciting 2010-2013), GSRT Operation Program “Competitiveness and Entrepreneurship” NSRF (2007-2013) etc. SCIENTIF RESPONSIBLE OF RESEARCH PROJECTS: 1. National Strategic Reference Framework (NSRF) - Program ARISTEIA 2012-2015 BIOPROPSHIP

«Augmenting ship propulsion in rough seas by biomimetic wing systems», funded by Greek Secretariat for Research and Technology.

2. Operational Programme for Education and Initial Vocational Training (2003-08), ΕΠΕΑΕΚ II-Archimedes - Support of research groups - Environmental and ecology subjects: «Prediction methods of waves in marine and coastal environment with application to development of naval technology for the application of novel oil-spill combating technique», funded by Greek Ministry of Education.

3. Operational Programme for Education and Initial Vocational Training EPEAEK-II (2003-08), Department of Naval Architecture of Technological Educational Institute of Athens: Development of small water tank supporting experiments at small scale concerning ship stability, ship resistance, wave propagation and wave-floating body interaction experimental studies, funded by Greek Ministry of Education.

4. Operational Programme for Education and Initial Vocational Training EPEAEK-II (2003-08), Department of Naval Architecture of Technological Educational Institute of Athens: Development of marine engineering laboratory equipped with a Diesel engine testbed and a water piping system, and measuring equipment for exhaust gas emissions and sound and vibration measurements, funded by Greek Ministry of Education.

REVIEWER IN INTERNATIONAL JOURNALS - SESSION ORGANIZER IN INTERNATIONAL CONFERENCES:

Reviewer in International Scientific Journals (Journal of Fluid Mechanics, Engineering Analysis with Boundary Elements, Engineering Structures, Applied Ocean Research, Ocean Engineering, Marine Structures, Adv.Water Resources, Journal of Physical Oceanography, European Journal of Fluid Mechanics, Natural Hazards, Journal Computational Acoustics, Computer Methods in Applied Mechanics and Engineering, Journal of Engineering for the Maritime Environment κ.α.) καί σε διεθνή συνέδρια (ISOPE, IMAM, OMAE, MARTECH, EWTEC, RENEW κ.α.)

Member of the Scientific Committee of International Conference on Ocean Οffshore & Αrctic Εngineering (OMAE) Ocean Engineering Symposium.

Session Organizer & session chair in the subject of Wave Mechanics and Wave Εffects ΟΜΑΕ 2006-2013

Session Organizer in the subject Coastal Studies and Wave Spectra of the International Conference IMAM 2005, IMAM 2011, IMAM2013

Session Organizer in the subject Waves and Current of ICHD2008

EGU Nonlinear Processes in Geosciences - Nonlinear Waves co-convener 2014,2015,2016,2017

Funded Visits:

Dept. of Oceanography, Naval PostGraduate School, Monterey, Oct. 2003, for implementation of coupled-mode model to Nearshore Canyon Experiment (NCEX) in Scripps nearshore area, San Diego, California.

Trondheim - Norway Oct. 2004 for participating the Int. Workshop Very Large Floating Structures for the Future, organised CeSOS – NTNU.

Visiting Professor, University of Toulon, SeaTech & Institut Méditerranéen d’Océanologie (MIO), Sept. 2014, Oct. 2015, Sept.2016

Visiting Professor, Ecole Central Marseille, September 2015

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RESEARCH AREAS (AND CLASSIFICATION OF PAPERS):

1. Wave phenomena in the sea: surface gravity waves and acoustic waves (ocean acoustics). Modelling of wave propagation and scattering in inhomogeneous environment and applications

Free surface: a.6, a.7, a.8, a.10, a.11, a.13, a.14, a.15, a.16, a.17, a.18,a.19, a.20, hydrodynamics a.21, a.22, a.23, a.24, a.26, a.28, a.29, a.30, a.31, a.32, a.35, a.39, a.40, a.42, a.43, a.45, a.46, a.47, a.48, a.49

b.7, b.9, b.10, b.13, b.14, b.15, b.17, b.18, b.19, b.20, b.21, b.22, b.23, b.24, b.25, b.26, b.28 b.29, b.31, b.32, b.33, b.34, b.36, b.38, b.39,

b.40, b.41, b.42, b.43, b.44, b.46, b.47, b.48, b.49, b.50, b.55, b.56, b.59, b.62, b.68, b.74, b.75, b.88, b.92, b.93, b.94, c.5, c.9, c.10, c.18, c.19, c.25

hydroacoustics: a.3, a.25, a.27, a.38, b.5, b.12, b.17, b.35, b.60, b.65, b.80, b.88 c.1, c.2, c.3, c.6, c.8, c.12, c.13, c.14, c.21 coupled-mode methods in elastic, aeroacoustic and ElectroMagnetic waveguides: b.60, b.69, b.74, c.4, c.7, c.11 2. Ship and marine hydrodynamics, wave-body-seabed interaction in general bathymetry a.15, a.16, a.26, a.28, a.29, a.33, a.34, a.35, a.39, a.40, a.41, a.42, a.43, a.44, a.45, a.47, a.48,

a.49, b.21, b.23, b.24, b.26, b.49, b.50, b.55, b.56, b.57, b.58, b.59, b.62, b.63, b.64, b.66, b.68, b.70, b.71, b.72, b.73, b.74, b.76, b.78, b.79, b.81, b.83, b.84, b.87, b.89, b.90, b.91, b.96, b.97,c.23, c.24, c.25, c.26, p.2

3. Technological applications in ship and marine hydrodynamics, flows with vorticity, lifting flows, marine propellers:

a.2, a.4, a.5, a.9, a.13, a.33, a.35, a.36, a.37, a.41, a.44, b.1, b.2, b.3, b.4, b.6, b.8, b.11, b.30, b.45, b.51, b.52, b.53, b.54, b.61, b.64, b.67, b.70, b.72, b.76, b.77, b.81, b.82, b.83, b.84, b.86, b.87, b.89, b.91, b.92, b.95, b.96, c.20, c.22, c.23, c.26, p.3,p.4

4. Wind wave climate and energy potential (statistical) description:

a.1, a.12, a.46, a.50, b.16, b.19, b.20, b.27, b.37, b.42, b.85, c.15, c.16, c.17, p.1 IMPACT FACTOR of journal papers by IF and SCIMAGO ranking (2016) . Journal no of papers Ιmp. Factor SJR(Quartile) CompMethApplMechEng 1 3.915 2.952(Q1) JPhysO ceanography 1 3.026 2.622(Q1) JGeophysicalRes. 1 3.303 2.310(Q1) Ocean Modelling 1 3.419 2.141(Q1) Coastal Engineering 2 2.829 1.999(Q1) Marine Structures 1 1.729 1.746(Q1) Progr. Oceanography 1 4.214 1.726(Q1) JFluidMechanics 5 2.514 1.450(Q1) JSoundVibration 1 2.300 1.494(Q1) AppliedOceanResearch 8 1.594 1.315(Q1) Eng.Anal.BoundaryElem. 3 1.802 1.251(Q1) Ocean Engineering 5 1.773 1.240(Q1) JAcoust.Soc.America 1 3.143 0.938(Q1) Proc.Roy.Soc.A 1 2.450 0.894(Q1) Wave Motion 2 1.325 0.668(Q2) JComp.Acoustics 1 0.852 0.583(Q2)

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ADMINISTRATIVE EXPERIENCE

Participation in administration 2003-2008 Scientific Responsible of Ship Technology section of the Dept of Naval Architecture of

Technological Educational Institute of Athens (http://www.na.teiath.gr/index_en.html) 2008-2010 Head of Dept. of Naval Architecture of Technological Educational Institute of Athens 2011-today Participated in several Committees of the School of Naval Architecture & Marine

Engineering NTUA 2014-today Director of the Section of Ship & Marine Hydrodynamics, School of Naval Architecture &

Marine Engineering NTUA 2016-today Member of Dean’s Committee of School of Naval Architecture & Marine Engineering

NTUA

Participation in Committees for the election of faculty (academic) members From 2003 until today participated in a number of Committees for the election of faculty members at the Technological Educational Institute of Athens (Dept. of Naval Architecture, Dept. of Civil Engineering & Infrastructure, Dept of Energy Technology, and as member of several of corresponding recommendatory committees. Also, from 2011 until today participated in a number of of Committees for the election of faculty members of National Technical University of Athens and University of Thessaly.

PROFESSIONAL EXPERIENCE AS NAVAL ARCHITECT IN ELEUSIS SHIPYARDS S.A. 1994-1995: Naval Architect & Marine Engineer Engineer at the Department of Planning of the Eleusis Shipyards S.A. Participated in the design team and implementation of Management Systems and Total Quality Management (TQM), by the ISO-9001 standards. 1992-1994: During the fulfillment of military service in the Greek Navy served as Petty Officer (Engineer) in the Hellenic Navy Detachment at Eleusis Shipyards, participating in the team of engineers supervising the construction of five new Landing Ships. MEMBER IN TECHNICAL CHAMBERS AND SCIENTIFIC SOCIETIES a. Technical Chamber of Greece b. Association of Naval Architects and Marine Engineers of Greece c. Society of Naval Architects & Marine Eng. (SNAME) d. Royal Institute of Naval Architects (RINA)

PUBLICATIONS: 50 journal papers (6 as single author, 15 as first author) 123 papers in International Conference proceedings (97 based on full text review, 26 based on

abstract review) 17 single-authored papers (6 journals and 11 Conference proceedings)

CITATIONS (October 2016)

Scopus 875 (530) h-index 14 (11) Web of Science 707(603) h-index 13 Google Scholar 1476 h-index 18, i10- index 33

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WORKS FOR THE ACQUISITION OF ACADEMIC TITLE

PhD thesis

Belibassakis K., 1992, “A velocity based Boundary Element Method for the analysis of marine propellers in unsteady flow”, Ph.D. Thesis Dept. of Naval Architecture & Marine Engineering, National Technical University of Athens.

Diploma thesis

Belibassakis K., 1986, “Application of panel methods to marine propeller design”, Diploma Thesis Dept. of Naval Architecture & Marine Engineering, National Technical University of Athens.

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LIST OF PUBLICATIONS A. JOURNAL PAPERS

1. Athanassoulis, G.A., Skarsoulis, E.K., Belibassakis, K.A., 1994, Bivariate Distributions with Given Marginals with an Application to Wave Climate Description, Applied Ocean Research, Vol.16, pp. 1-17.

2. Belibasakis, K.A., Politis G.K., 1995, A Boundary Integral Equation Formulation of the Neumann Problem for a Vector Field in R3 with Application to Potential Lifting Flows, Engineering Analysis with Boundary Elements, Vol.16, pp.5-17.

3. Athanassoulis, G.A., Belibassakis, Κ.Α., 1997, All-frequency normal-mode solution of the 3D acoustic scattering from a vertical cylinder in a plane horizontal waveguide, Journal of the Acoustical Society of America, Vol. 101, pp. 3371-3384.

4. Loukakis, Th, Bardis, L.,.., Belibassakis, K., et al, 1997, A computer aided ship design system, Techn. Chron. Sci. J., TCG, Vol. 17, No.1.

5. Belibasakis, K.A. Politis, G.K., 1998, A Non-Linear Velocity Based Boundary Element Method for the Analysis of Marine Propellers in Unsteady Flow, International Shipbuilding Progress, Vol. 45, pp. 93-133.

6. Athanassoulis, G.A., Belibassakis, K.A., 1999, A consistent coupled-mode theory for the propagation of small-amplitude water waves over variable bathymetry regions, Journal of Fluid Mechanics, Vol 389, pp275-301.

7. Belibassakis, K.A., 2000, The Green’s function of the mild-slope equation, Wave Motion, Vol.32, pp. 339-361.

8. Belibassakis, K.A., Athanassoulis, G.A., Gerostathis, Th., 2001, A coupled-mode system for the refraction-diffraction of linear waves over steep three dimensional topography, Applied Ocean Research, Vol. 23, pp. 319-336.

9. Belibassakis, K.A., Politis G.K., 2002, Analysis of unsteady propeller performance by a surface vorticity panel method, Schiffstechnik-Ship Technology Research, Vol. 49, pp.13-21.

10. Athanassoulis, G.A., Belibassakis, K.A., Gerostathis, Th., 2002, The POSEIDON nearshore wave model and its application to the prediction of the wave conditions in the nearshore/coastal region of the Greek Seas, Global Athmosphere and Ocean System (GAOS), Vol 8 (2-3), 101-117.

11. Belibassakis, K.A., Athanassoulis, G.A., 2002, Extension of second-order Stokes theory to variable bathymetry, Journal of Fluid Mechanics, Vol. 464, pp. 35-80.

12. Athanassoulis, G.A., Belibassakis, K.A., 2002, Probabilistic description of metocean parameters by means of kernel density models. Part 1: Theoretical background and first results, Applied Ocean Research, Vol. 24, pp.1-20.

13. Belibassakis, K.A., 2003, A coupled-mode technique for the transformation of ship-generated waves over variable bathymetry regions, Applied Ocean Research, Vol. 25, pp.321-336.

14. Belibassakis, K.A., Athanassoulis, G.A., 2004, Three-dimensional Green's function of harmonic water-waves over a bottom topography with different depths at infinity, Journal of Fluid Mechanics, Vol. 510, pp.267-302.

15. Belibassakis, K.A., Athanassoulis, G.A., 2005, A coupled-mode model for the hydroelastic analysis of large floating bodies over variable bathymetry regions, Journal of Fluid Mechanics Vol. 531, pp.221-249.

16. Belibassakis, K.A., Athanassoulis, G.A., 2006, A coupled-mode technique for weakly non-linear wave interaction with large floating structures lying over variable bathymetry regions Applied Ocean Research Vol.28, 59-76.

17. Magne, R., Belibassakis, K., Herbers, T., Ardhuin, F., O'Reilly, Rey, V. 2007, Evolution of surface gravity waves over a submarine canyon, Journal of Geophysical Research (JGR Oceans), Vol.112, C01002, doi:10.1029/2005JC003035.

18. Belibassakis, K.A., 2007, A coupled-mode model for the scattering of water waves by shearing currents in variable bathymetry, J. Fluid Mech. Vol. 578, 413-434.

19. Athanassoulis, G.A., Belibassakis, K.A., 2007, A coupled-mode method for non-linear water waves in general bathymetry with application to steady travelling solutions in constant, but arbitrary, depth, Journal Discrete and Continuous Dynamical Systems DCDS-B, pp. 75-84 (special volume of selected papers from 6th Int. Conference on Dynamical Systems and Differential Equations, Poitiers Meeting, June 25-28, 2006).

20. Gerostathis, Th., Politis, K., Belibassakis, K.A., Athanassoulis, G.Α., 2007, A Wavelet Galerkin technique for the wave-current-seabed interaction in variable bathymetry regions, Bulletin of the Greek Mathematical Society, Vol.54, 167-178.

21. Cavaleri, L, et al (2007), Wave modeling – State of the art, Progress in Oceanography, Vol. 75, 603-674.

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22. Gerostathis, T., Belibassakis, K.A., Athanassoulis, G.A., 2008, A coupled-mode model for the transformation of wave spectrum over steep 3d topography. A Parallel-Architecture Implementation, Journal of Offshore Mechanics and Arctic Engineering, JOMAE, Vol.130

23. Ardhuin, F., Rascle, N., Belibassakis, K.A., 2008, Explicit wave-averaged primitive equations using a Generalized Lagrangian Mean, Journal of Ocean Modelling, Vol.20, 35-60.

24. Ardhuin, F., Jenkins, A., Belibassakis, K.A., 2008, Commentary on `The Three-Dimensional Current and Surface Wave Equations' by George Mellor, Journal of Physical Oceanography-JPO, Volume 38(6), pp. 1340–1350.

25. Athanassoulis, G.A., Belibassakis, K.A., Mitsoudis, D.A., Kampanis, N.A., Dougalis, V.A., 2008, Coupled-mode and finite-element solutions of underwater sound propagation problems in stratified acoustic environments, 2008, Journal of Computational Acoustics – JCA, Vol.16(1), pp.83-116.

26. Belibassakis, K.A., 2008, A boundary element method for the hydrodynamic analysis of floating bodies in general bathymetry regions, Engineering Analysis with Boundary Elements, 32 (2008), pp. 796-810.

27. Prospathopoulos, A. M., Athanassoulis, G.A., Belibassakis, K.A., 2009, Three-dimensional acoustic field computations for scattering from a radially-layered cylindrical obstacle in an ocean waveguide: Low-frequency results, J. of Sound and Vibration, Vol. 319, pp.1285-1300.

28. Athanassoulis, G.A., Belibassakis, K.A., 2009, A novel coupled-mode theory with application to hydroelastic analysis of thick, non-uniform floating bodies over general bathymetry, Journal of Engineering for the Maritime Environment,Vol.223, pp.419-437.

29. Belibassakis, K.A., 2010, Roll response of ship-hull sections in variable bathymetry regions by a hybrid BEM - vortex particle method, Journal of Hydrodynamics Ser. B, Volume 22, Issue 5, Supplement 1, October 2010, Pages 413-418 (selected papers from 9th Intern. Conference on Hydrodynamics, ICHD 2010, Shanghai, China).

30. Belibassakis, K.A., Athanassoulis, G.A., 2011, A coupled-mode system with application to nonlinear water waves propagating in finite water depth and in variable bathymetry regions, Coastal Engineering Vol. 58, pp.337-350.

31. Belibassakis, K.A., Gerostathis, Th., Athanassoulis, G.A., 2011, A coupled-mode model for water wave scattering by horizontal, non-homogeneous current in general bottom topography, Applied Ocean Research, Vol.33, pp. 384– 397

32. Belibassakis, 2012, Water-wave induced groundwater pressure and flow in variable bathymetry regions and sandy beaches by an enhanced coupled-mode model, Ocean Engineering Vol. 47, pp. 104–118.

33. Belibassakis K.A., Gerostathis, Th.P, Kostas K.V., Politis C.G., Kaklis P.D., Ginnis A.I., Feurer C., 2013, A BEM-isogeometric method for the ship wave-resistance problem, Ocean Engineering Vol. 60, pp. 53–67.

34. Belibassakis K.A., Politis G.K., 2013, Hydrodynamic performance of flapping wings for augmenting ship propulsion in waves, Ocean Engineering Vol.72, pp.227-240.

35. Belibassakis, Κ.Α., Tsoukala VK., Katsardi V., 2014, Three dimensional wave diffraction in the vicinity of openings in coastal structures, Applied Ocean Research, Vol.45, 40-54

36. Filippas, E., Belibassakis K.A., 2014, Hydrodynamic analysis of flapping-foil thrusters operating beneath the free surface and in waves, Engineering Analysis with Boundary Elements, Vol.41, 47-59.

37. Diakaki Chr., Panagiotidou N., Pouliezos A., Kontes G, Stavrakakis G., Belibassakis K., Gerostathis Th., Livanos G., Pagonis D.-N., Theotokatos G., 2014, A decision support system for the development of voyage and maintenance plans for ships, Inter. Journal of Decision Support Systems (InterScience Publishers, in press).

38. Belibassakis K.A., Athanassoulis G.A., Papathanassiou T.K., Filopoulos, S.P., Markolefas S., 2014, Acoustic wave propagation in inhomogeneous, layered waveguides based on modal expansions and hp-FEM, Wave Motion, Vol. 51, 1021-1043.

39. Papathanasiou T.K., Belibassakis K.A., 2014, Hydroelastic analysis of VLFS based on a consistent coupled mode system and FEM, The IES Journal Part A: Civil & Structural Engineering, Taylor & Francis, Vol. 7, No. 3, 195-206.

40. Belibassakis, K.A., Athanassoulis, G.A., Gerostathis, Th., 2014, Directional wave spectrum transformation in the presence of strong depth and current inhomogeneities by means of coupled-mode model, Ocean Engineering, Vol. 87, 84–96.

41. Ginnis A.I., Kostas K.V., Politis C.G., Kaklis P.D., Belibassakis K.A., Gerostathis, Th.P, Scott M.A., Hughes T.J.R., 2014, Isogeometric boundary-element analysis for the wave-resistance problem using T-splines, Computer Methods in Applied Mechanics and Engineering, Vol.279, 425-439.

42. Tsoukala VK., Katsardi V., Belibassakis, Κ.Α., 2014, Wave transformation through flushing culverts operating at seawater level in coastal structures Ocean Engineering Vol.89, 211–229.

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43. Papathanasiou T. K., Karperaki A., Theotokoglou E.E., Belibassakis K.A., 2015, A higher order FEM for time-domain hydroelastic analysis of large floating bodies in inhomogeneous shallow water environment, Proc. Royal Society of London A: Mathematical, Physical and Engineering Sciences . A Vol. 471: 20140643.

44. Belibassakis K.A., Filippas, E., 2015, Ship propulsion in waves by actively controlled flapping foils, Applied Ocean Research Vol. 52, 1–11

45. Papathanasiou T.K., Karperaki A.,Theotokoglou E.E., Belibassakis K.A., 2015, Hydroelastic analysis of ice shelves under long wave excitation, Nat. Hazards Earth Syst. Sci., Vol.15, 1851–1857.

46. Tsoukala, V., Chondros, M.,…, Belibassakis, K.A., Makropoulos, Ch., 2016, An integrated wave modelling framework for extreme and rare events for climate change in coastal areas – the case of Rethymno-Crete, Oceanologia Vol. 58, 71-89.

47. Gerostathis Th., Belibassakis K.A., Athanassoulis G.A., 2016, 3D hydroelastic analysis of very large floating bodies over variable bathymetry regions, Journal of Ocean Engineering and Marine Energy Vol.2, 159-175.

48. Karperaki A., Belibassakis K.A., Papathanasiou T. K., 2016, Time-domain, shallow-water hydroelastic analysis of VLFS elastically connected to the seabed, Marine Structures Vol. 48, 33-51.

49. Touboul J., Charland J., Rey V., Belibassakis K., 2016, Extended Mild-Slope equation for surface waves interacting with a vertically sheared current Coastal Engineering Vol. 116, 77–88.

50. Makris Ch., Galiatsatou P., …., Belibassakis Κ., Rusu E., 2016, Climate change effects on the marine characteristics of the Aegean and Ionian Seas, Ocean Dynamics, DOI10.1007/s10236-016-1008-1.

51. Belibassakis K.A., Karathanassi F.E., 2017, Modelling nearshore hydrodynamics and circulation under the impact of high waves at the coast of Varkiza in Saronic-Athens Gulf, Oceanologia Vol. 59(3), 350-364.

52. Belibassakis K.A., Simon B., Touboul J., Rey V., 2017, A coupled-mode model for water wave scattering by vertically sheared currents in variable bathymetry regions, Wave Motion Vol.74, 73-92.

53. Papoutsellis, Ch, Belibassakis, K.A., Athanassoulis, G.A. 2017, An exact Hamiltonian coupled-mode system with application to extreme design waves over variable bathymetry, to appear in special issue on Rogue Waves, Journal of Ocean Engineering and Marine Energy.

B. CONFERENCE PAPERS (reviewed on the basis of full text)

1. Politis, G.K., Belibasakis, K.A., Nakos, D., 1987, Panel Methods vs Vortex Lattice Methods in Marine Propeller Design, 4th International Congress of the International Maritime Association of East Mediterranean, IMAEM’87, Varna, Bulgaria.

2. Belibasakis, K.A., Politis, G.K., 1989, Calculation of Three Dimensional Potential Flows using Surface Vorticity Distributions, 5th Int. Conference on Computational Methods and Experimental Measurements, CMEM'89, Capri, Italy.

3. Belibasakis, K.A., Politis, G.K., 1989, Calculation of Three Dimensional Lifting Flows using Surface Vorticity Distributions, 4th Int. Symp. on Practical Design of Ships, PRADS'89, Varna, Bulgaria.

4. Politis, G.K., Belibasakis, K.A., 1990, Application of Panel Methods to Linearized Lifting Surface Propeller Performance Problem, 5th Intern Congress on Marine Technology, IMAEM'90, Athens, Greece.

5. Athanassoulis, G.A., Belibassakis, K.A, 1997, The integrated software Amfitrite with application to hydroacoustic calculations in the Greek Sea environment, 5th Hellenic Symposium of Oceanography, Kavala, Greece, April 1997 (in Greek).

6. Belibassakis, K.A., Politis, G.K., Triantafyllou, M.S., 1997, Application of the Vortex Lattice Method to the propulsive performance of a pair of oscillating wing-tails, Proc. 8th Inter. Conf on Computational Methods and Experimental Measurements, CMEM’97, Rhodes, Greece.

7. Athanassoulis, G.A., Belibassakis, K.A., 1997, Water wave Green function for a 3D uneven-bottom problem with different depths at infinity, Proc. IUTAM Symposium on Computational Methods in Unbounded Domains, Intern. Union of Theoretical and Applied Mechanics, University of Colorado, U.S.A., July 1997, Kluwer.

8. Politis, K.A., Belibassakis, K.A., 1999, High propulsive efficiency by a system of oscillating wing tails, 9th Inter. Conf. on Computational Methods and Experimental Measurements, CMEM’99, Sorrento, Italy, 1999.

9. Athanassoulis, G.A., Belibassakis, K.A., 1999, A coupled-mode propagation/dissipation model of small-amplitude water waves over variable bathymetry regions, Coastal Engineering 99, Lemnos, Greece 1999.

10. Athanassoulis, G.A., Belibassakis, K.A., Gerostathis, Th., 2000, A coupled-mode theory for the diffraction of water waves by localized scatterers over a parallel-contour bathymetry, WAVES

11

2000 Mathematical and Numerical Aspects of Wave Propagation, organized by SIAM and INRIA, Spain, June 2000.

11. Belibassakis K.A., Politis G.K., 2002, Unsteady performance of propellers with non-conventional blade geometry by a vorticity based panel method, 10th Congress of International Maritime Association of the Mediterranean, ΙΜΑΜ 2002, Rethymnon-Crete.

12. Athanassoulis, G.A., Belibassakis, K.A., Gerostathis, Th., 2002, A coupled-mode model for acoustic scattering by a general seafloor topography, 10th Congress of International Maritime Association of the Mediterranean, ΙΜΑΜ 2002, Rethymnon-Crete.

13. Belibassakis, K.A., Athanassoulis, G.A., 2002, Harmonic generation past a generally shaped bottom profile, 10th Congress of International Maritime Association of the Mediterranean, ΙΜΑΜ 2002, Rethymnon-Crete.

14. Athanassoulis, G.A., Belibassakis, K.A., 2002, A Coupled-Mode, Fully-dispersive, Weakly-nonlinear Model for Water Waves over a General Bathymetry, 12th Intern. Offshore and Polar Conference and Exhibition, ISOPE2002, Kitakyushu, Japan

15. Athanassoulis, G.A., Belibassakis, K.A., 2002, A nonlinear coupled-mode model for water waves over a general bathymetry, 21st International Conference on Offshore Mechanics and Arctic Enginnering, OMAE2002 Oslo, Norway

16. Athanassoulis, G.A., Belibassakis, K.A., Stefanakos, Ch.N, 2002, Wave power prediction in nearshore areas based on offshore wave information. A case study, 21st IASTED, Power and Energy Systems (EuroPES 2002), Crete, Greece.

17. Athanassoulis, G.A., Belibassakis, 2003, Rapidly-convergent local-mode representations for wave propagation and scattering in curved-boundary waveguides, 6th Int. Conference on Mathematical and Numerical Aspects of Wave Propagation (WAVES 2003), organized by SIAM and INRIA, Finland

18. Athanassoulis, G.A., Belibassakis, K.A., Georgiou Y., 2003, Transformation of the Point Spectrum over Variable Bathymetry Regions, 13th Intern. Offshore and Polar Conference and Exhibition, ISOPE2002, Honolulu, Hawaii, USA.

19. Barstow, S., Mørk, G., Lønseth L, Schjølberg, P., Machado, U., Athanassoulis, G., Belibassakis, K., Gerostathis, T., Stefanakos, Ch., Spaan, G., 2003, WORLDWAVES: Fusion of data from many sources in a user-friendly software package for timely calculation of wave statistics in global coastal waters, 13th Intern. Offshore and Polar Conference and Exhibition, ISOPE2003, Honolulu, Hawaii, USA.

20. Barstow, S., Mørk, G., Lønseth L, Schjølberg, P., Machado, U., Athanassoulis, G., Belibassakis, K., Gerostathis, T., Stefanakos, Ch., Spaan, G., 2003, WORLDWAVES: High quality coastal and offshore wave data within minutes for any global site, 22nd International Conference on Offshore Mechanics and Arctic Engineering, OMAE2003, Cancun, Mexico.

21. Belibassakis K.A. and Athanassoulis G.A., 2004, Hydroelastic responses of Very Large Floating Structures lying over variable bathymetry regions, 14th Intern. Offshore and Polar Conference and Exhibition, ISOPE2004, Toulon, France.

22. Belibassakis K.A. and Athanassoulis G.A., 2004, A Coupled-Mode technique for wave-current interaction in variable bathymetry regions, 14th Intern. Offshore and Polar Conference and Exhibition, ISOPE2004, Toulon, France.

23. Belibassakis K.A. and Athanassoulis G.A., Hydroelastic behavior of floating flexible plates on surface gravity waves with the effects of variable bathymetry, 7th National Congress on Mechanics HSTAM 2004, June 24-26, 2004, Chania-Crete, Greece.

24. Belibassakis, K.A., 2004, Hydrodynamic analysis of floating bodies in variable bathymetry regions, 1st Intern. Conference from Scientific Computing to Computation Engineering IC-SCCE, Athens, Greece, 2004.

25. Belibassakis, K.A., Stephanakos, C.N, Bratsos, A., Prospathopoulos, A., 2004, Numerical simulation of weakly nonlinear wave propagation in variable bathymetry regions, Intern. Conference of Numerical Analysis and Applied Mathematics (ICNAAM 2004), Chalkis, Greece, 10-14 Sept. 2004.

26. Belibassakis, K.A., 2005, Hydrodynamic Analysis of Floating Bodies in General Bathymetry, 24th International Conference on Offshore Mechanics and Arctic Engineering, OMAE2005, Halkidiki, Greece.

27. Stefanakos, Ch., Belibassakis, K.A., 2005, Nonstationary Stochastic Modelling Of Multivariate Long-Term Wind And Wave Data, 24th International Conference on Offshore Mechanics and Arctic Engineering, OMAE2005, Halkidiki, Greece.

28. Gerostathis, T., Belibassakis, K.A., Athanassoulis, G.A., 2005, A Coupled-Mode, Phase-Resolving Model For The Transformation Of Wave Spectrum Over Steep 3D Topography. A Parallel-Architecture Implementation, 24th International Conference on Offshore Mechanics and Arctic Engineering, OMAE2005, Halkidiki, Greece.

29. Belibassakis, K.A., 2005, Propagation of water waves through shearing currents in general bathymetry International Maritime Association of the Mediterranean, Maritime Transportation and Exploitation of Ocean and Coastal Resources, IMAM2005, Lisbon, Portugal

12

30. Belibassakis, K.A., Hatzikostandis, G.K, Theotokatos G,. Stefanakos Ch.N., Sarantopoulos S., Gerostathis Th., Georgiou Y.G, New challenges in the education of Naval Architects in TEI of Athens, WSEAS Intern. Conference on Engineering Education, Athens, Greece, July 8-10, 2005.

31. Bratsos, A., Belibassakis, K.A., Natsis, D.G., Papadopoulos, D.P., 2005, On the numerical modeling of a shallow water equation, 17th IMACS World Congress on Scientific Computation, Applied Mathematics and Simulation, 11-15 July 2005, Paris, France (paper T1-I-28-0176).

32. Bratsos A. G., Famelis I. Th. and K. A. Belibassakis, 2005, An implicit numerical method for a shallow water equation in 2+1 dimensions, International Conference of Numerical Analysis and Applied Mathematics, ICNAAM2005, Rhodes, Greece, 16-20 Sept. 2005, Wiley-VCH, pp. 103-106.

33. Athanassoulis, G.A., Belibassakis, K.A., 2005, Nonlinear water-wave problem: A consistent coupled-mode reformulation and derivation of families of travelling wave solutions, 7th Int. Conference on Mathematical and Numerical Aspects of Wave Propagation (WAVES 2005), Brown University, USA.

34. Belibassakis K.A. and Athanassoulis G.A., 2006, A coupled mode technique for the run-up of non-breaking dispersive waves on plane beaches, 25th International Conference on Offshore Mechanics and Arctic Engineering, OMAE2006, Hamburg, Germany.

35. Xiros N.I., Belibassakis K.A., Athanassoulis G.A., 2006, Modeling and Assessment of the Underwater Acoustic Channel for Submerged End-Users Positioning Information Transmission and Applications, 16th Intern. Offshore and Polar Conference and Exhibition, ISOPE2006, San Fransisco.

36. Gkikas G.D., Xiros N.I., Athanassoulis G.A. and Belibassakis K.A., 2006, A nonlinear model for Oscillating Water Column analysis, design and control, 16th Intern. Offshore and Polar Conference and Exhibition, ISOPE2006, San Francisco.

37. Athanassoulis, G.A., Belibassakis, K.A., Gerostathis, T., 2006, Wave data along ship routes in the Mediterranean Sea, 9th Int Conf. on Stability od Ships and Ocean Vehicles, STAB2006, Rio de Janeiro, Brazil.

38. Athanassoulis, G.A., Belibassakis, K.A., 2006, A new unified theory for nonlinear steady travelling waves in constant, but arbitrary, depth , 7th Intern. Conference on Hydrodynamics, ICHD 2006, Ischia, Italy.

39. Belibassakis, K.A., Gerostathis, T., Athanassoulis, G.A., 2007, A phase-resolving, coupled-mode model for wave-current-seabed interaction over steep 3D bottom topography. Parallel architecture implementation, 17th Intern. Offshore and Polar Conference and Exhibition, ISOPE2007, Lisbon

40. Belibassakis, K.A., Athanassoulis, G.A., 2007, A coupled-mode technique for the prediction of wave-induced set-up in variable bathymetry domains and groundwater circulation in permeable beaches, 17th Intern. Offshore and Polar Conf. and Exhibition, ISOPE2007, Lisbon

41. Belibassakis, K.A., Gerostathis, T., Athanassoulis, G.A., 2007, Calculation of wave-induced set-up in variable bathymetry regions and groundwater flow in permeable beaches by a coupled-mode method, 8th HSTAM International Congress on Mechanics, Patras, Greece.

42. Belibassakis K.A., Stefanakos, C.N., Georgiou, Y., 2007, Extreme value predictions on decreasing depth by means of a nonlinear wave transformation model, 26th International Conference on Offshore Mechanics and Arctic Engineering, OMAE2007, San Diego, USA.

43. Belibassakis K.A., Th.P. Gerostathis and Athanassoulis G.A., 2007, A coupled-mode technique for the prediction of wave-induced set-up and mean flow in variable bathymetry domains 26th Int. Conference on Offshore Mechanics and Arctic Engineering, OMAE2007, San Diego, USA.

44. Belibassakis, K.A., Gerostathis, T., Athanassoulis, G.A., 2007, Wave-current systems in variable bathymetry regions, 12th International Congress of the International Maritime Association of the Mediterranean IMAM2007, Varna Boulgaria

45. Belibassakis, K.A., Chatzikostandis, G, Georgiou Y., 2007, Optimisation of naval technology for novel oil-spill combating technique, 12th International Congress of the International Maritime Association of the Mediterranean IMAM2007, Varna Boulgaria.

46. Athanassoulis G.A., Belibassakis K.A., 2008, A unified coupled-mode approach to nonlinear waves in finite depth. Potential flow. 27th International Conference on Offshore Mechanics and Arctic Engineering, OMAE2008, Estoril, Portugal.

47. Belibassakis, K.A., Gerostathis, T., Athanassoulis, G.A., 2008, A weakly nonlinear couple-mode model for wave-current-seabed interaction over general bottom topography, 27th International Conference on Offshore Mechanics and Arctic Engineering, OMAE2008, Estoril, Portugal.

48. Belibassakis, K.A., Athanassoulis, G.A., 2008, A coupled-mode approach to nonlinear waves in finite depth. Viscous bottom boundary-layer flow, 8th Intern. Conference on Hydrodynamics, ICHD 2008, Nantes, France.

49. Belibassakis, K.A., Athanassoulis, G.A., 2009, A fast convergent modal-expansion of the wave potential with application to the hydrodynamic and hydroelastic analysis of floating bodies in general bathymetry,28th International Conference on Offshore Mechanics and Arctic Engineering, OMAE2009, Hawaii.

50. Belibassakis, K.A., Athanassoulis, G.A., 2009, A coupled-mode model with application to wave

13

scattering by VLFS or ice sheets of varying thickness over general bottom topography , 5th Int. Conf. on Hydroelasticity in Marine Technology, Southapton.

51. Politis, C, Ginnis, A., Kaklis, P., Belibassakis, K., Feurer, C., 2009, An isogeometric BEM for exterior potential-flow problems in the plane. SIAM - ACM Joint Conference on Geometric Design, San Francisco.

52. Belibassakis, K., A combined panel method / coupled-mode technique for the spatial evolution of ship-generated wave systems over variable bathymetry regions, 10th International Conference on Fast Sea Transportation, FAST 2009, Athens, Greece.

53. Belibassakis, K., Gerostathis, Th, Politis, C., Kaklis, P., Ginnis, A., Mourkogianis, D., 2009, A novel BEM-isogeometric method with application to the wavemaking resistance problem of bodies at constant speed. Intern. Maritime Association Mediterranean Conference, IMAM 2009, Istanbul.

54. Belibassakis, K., 2009, Effects of wave-induced ship motion on propeller-hull interaction with application to fouling estimation and propulsion optimization. Internat. Maritime Association Mediterranean Conference, IMAM 2009 Istanbul.

55. Belibassakis, K.A., Gerostathis, Th.P., Athanassoulis, G.A., 2010, A coupled-mode model for the transformation of wave systems over inhomogeneous sea/coastal environment, 29th International Conference on Offshore Mechanics and Arctic Engineering, OMAE2010, Shanghai, China.

56. Belibassakis K.A. A coupled-mode model with application to the prediction of long-waves induced by short-wave groups, in general bathymetry regions, 9th HSTAM International Congress on Mechanics Limassol, Cyprus, 12 – 14 July, 2010

57. Belibassakis, K.A., 2010, Roll response of ship-hull sections in variable bathymetry regions by a hybrid BEM - vortex particle method, 9th Intern. Conference on Hydrodynamics, ICHD 2010, Shanghai, China.

58. Belibassakis, K., Gerostathis, Th, Kostas, K., Politis, C., Kaklis, P., Ginnis, A., Feurer, C., 2011, A BEM-isogeometric method with application to the wavemaking resistance problem of ships at constant speed. 30th International Conference on Offshore Mechanics and Arctic Engineering, OMAE2011, Rotterdam, The Netherlands.

59. Belibassakis, K., 2011, Infragravity waves induced by short-wave groups in coastal regions characterized by general bottom topography, 30th International Conference on Offshore Mechanics and Arctic Engineering, OMAE2011, Rotterdam, The Netherlands.

60. Athanassoulis, G.A., Belibassakis, 2011, A fast-convergent spectral method for wave propagation and scattering in non-uniform waveguides, 7th GRACM International Congress on Computational Mechanics, Athens June 2011.

61. Belibassakis, K., 2011, A panel method based on vorticity distribution for the calculation of free surface flows around ship hull configurations with lifting bodies. Intern. Maritime Association Mediterranean Conference, IMAM 2011, Genoa, Italy.

62. Belibassakis, K., 2011, A coupled-mode model for water-wave induced groundwater pressure and flow in variable bathymetry regions and beaches. Intern. Maritime Association Mediterranean Conference, IMAM 2011, Genoa, Italy.

63. Belibassakis K.A., Georgiou Y., Athanassoulis G.A. 2012, Interaction of Random Sea Waves with Floating Structures in General Bathymetry Regions, 22 International Offshore and Polar Engineering Conference Rhodes (ISOPE2012), Greece.

64. Belibassakis K.A., Politis, G.K., 2012, Hydrodynamic Analysis of Flapping Wing Systems for Augmenting Ship Propulsion in Rough Sea, 22 International Offshore and Polar Engineering Conference Rhodes (ISOPE2012), Greece.

65. Belibassakis K.A., Papathanasiou Th., Filopoulos S.P, 2012, A fast-convergent spectral method for harmonic wave propagation in inhomogeneous layered waveguides, 22 International Offshore and Polar Engineering Conference Rhodes (ISOPE2012), Greece.

66. Katsardi V., Boundris G., Tsoukala VK., Belibassakis K.A., 2012, Study of wave transformation due to flushing culverts in coastal structures, 22 International Offshore and Polar Engineering Conference Rhodes (ISOPE2012), Greece.

67. Belibassakis K.A., Politis, G.K., 2012, Roll stabilization by vertical thrust-producing flapping wings using active pitch control , Proceedings of the 11th International Conference on the Stability of Ships and Ocean Vehicles (STAB2012), 23-28 September 2012, Athens, Greece.

68. Belibassakis K.A., Athanassoulis G.A., Gerostathis Th.P. 2013, Hydroelastic analysis of Very Large Floating bodies over variable bathymetry regions , 10th HSTAM International Congress on Mechanics Chania, Crete, Greece, 25 – 27 May, 2013.

69. Belibassakis K.A., Athanassoulis G.A., Papathanasiou T.K. , Markolefas S.I., Kokkinos Tr., 2013, A coupled-mode system for shear deformable beams and plates of non-uniform thickness, 10th HSTAM International Congress on Mechanics Chania, Crete, Greece, 25 – 27 May, 2013.

70. Filippas, E., Belibassakis K.A., 2013, Free surface effects on hydrodynamic analysis of flapping foil thrusterS in waves, 32th International Conference on Offshore Mechanics and Arctic Engineering (OMAE2013), June 9-14, 2013 - Nantes, France.

14

71. Katsardi V., Tsoukala VK., Belibassakis K.A., 2013, Estimation of Wave Transmission through Flushing Culverts in Breakwaters Study of wave transformation due to flushing culverts in coastal structures, 32th International Conference on Offshore Mechanics and Arctic Engineering (OMAE2013), June 9-14, 2013 - Nantes, France.

72. Belibassakis K.A., Politis, G.K., Gerostathis Th.P. 2013, Calculation of ship hydrodynamic propulsion in rough seas by non-linear BEM with application to reduction of energy losses in waves, 32th International Conference on Offshore Mechanics and Arctic Engineering (OMAE2013), June 9-14, 2013 - Nantes, France.

73. Katsardi V., Tsoukala VK., Belibassakis K.A., 2013, 3D Wave Transformation through Openings in Coastal Structures, 32th International Conference on Offshore Mechanics and Arctic Engineering (OMAE2013), June 9-14, 2013 - Nantes, France.

74. Belibassakis K.A., Athanassoulis G.A., Papathanasiou Th., Filopoulos S.P, 2013, A coupled mode – hp FEM for the hydroelastic analysis of shear-deformable floating bodies of general thickness in variable bathymetry Computational Methods for Coupled Problems in Science and Engineering V, 17-19 June 2013, Ibiza, Spain.

75. Belibassakis K.A., Athanassoulis, G.A., Gerostathis Th.P., Katsardi V., 2013, Transformation of wave conditions in nearshore and coastal areas by a 3D coupled-mode wave model Intern. Maritime Association Mediterranean Conference, IMAM 2013, La Coruna, Spain

76. Filippas, E., Belibassakis K.A., 2013, A boundary element method for the hydrodynamic analysis of flapping-foil thrusters operating beneath the free surface and in waves, IMAM 2013, La Coruna, Spain.

77. Ginnis A.-A.I, Duvigneau R., Politis C., Kostas K., Belibassakis K., Gerostathis T., Kaklis P.D., 2013, A multi-objective optimization environment for ship-hull design based on a BEM-isogeometric solver, V International Conference on Computational Methods in Marine Engineering (MARINE 2013), Hamburg, Germany.

78. Papathanasiou T.K., Belibassakis K.A., 2014, Hydroelastic analysis of very large floating structures based on modal expansions and FEM, EUROPMENT 2014, Venice, Italy.

79. Chondros, M., Katsardi, V., Tsoukala, V.K., Belibassakis, K., 2014. Experimental verification of a new 3D numerical model involving wave transformation through flushing culverts, Proc. 3rd IAHR Europe Congress of International Association for Hydro-Environment Engineering and Research, Porto, Portugal.

80. Belibassakis K.A., Athanassoulis, G.A., 2014, A coupled-mode method for acoustic propagation and scattering in inhomogeneous waveguides, 33th International Conference on Offshore Mechanics and Arctic Engineering (OMAE2014), June 8-13, 2014, San Francisco CA.

81. Filippas, E., Belibassakis K.A., 2014, Hydrodynamic analysis of flapping-foil thruster operating in random waves, 33th International Conference on Offshore Mechanics and Arctic Engineering (OMAE2014), June 8-13, 2014, San Francisco CA.

82. Politis C.G., Papagiannopoulos A., Belibassakis K.A., Kaklis P.D., Kostas K.V., Ginnis A.I. Gerostathis T.P., 2014, An isogeometric BEM for exterior potential-flow problems around lifting bodies, 11th World Congress on Computational Mechanics (WCCM XI & ECCM V & ECFD VI), July 20-25, Barcelona, Spain.

83. Filippas, E., Belibassakis K.A., 2014, Design of flapping-foil thrusters for augmenting ship propulsion in waves, Proc.2nd International Conference on Maritime Technology and Engineering (MARTECH 2014), 2014 Lisbon, Portugal.

84. Tsarsitalidis V., Politis G.K., Belibassakis K.A., 2014, Flapping wing systems for augmenting ship propulsion in waves by employing systematic data, active control and exploiting hydroelastic effects, Proc. 9th International Conference on High-Performance Marine Vehicles (HIPER 2014), 2014, Athens, Greece.

85. Makropoulos, Ch, Tsoukala, V.K., Belibassakis, K., Lykou A., Chondros M., GOourgoura P., Nikolopoulos D., 2014, Managing flood risk in coastal cities through an integrated modelling framework supporting stakeholders’ involvement: The case of Rethymno, Crete, Proc. E-proceedings of the 36th IAHR World Congress 28 June – 3 July, 2015, The Hague, theNetherlands

86. Tsarsitalidis V., Politis G.K., Belibassakis K.A., 2015, Active and passive pitch-controlled flapping wing propulsors; Usage of the wake structure as performance qualifier, Proceedings VI International Conference on Computational Methods in Marine Engineering (MARINE 2015) Conference, Rome Italy.

87. Karperaki A., Belibassakis K.A., Markolefas, S., Papathanasiou T.K., 2015, Higher-order FEM for nonlinear hydroelastic analysis of a floating elastic strip in shallow-water conditions, PROC. International Conference on Computational Methods for Coupled Problems in Science and Engineering (COUPLED PROBLEMS 2015) 18 - 20 May 2015, Venice, Italy.

88. Belibassakis K.A. Athanassoulis, G.A.,Karperaki A., Papathanasiou T.K., Propagation of acoustic-gravity waves in inhomogeneous ocean environment based on modal expansions and hp-FEM, Proc. International Conference on Computational Methods for Coupled Problems in Science and

15

Engineering (COUPLED PROBLEMS 2015) 18 - 20 May 2015, Venice, Italy. 89. Belibassakis K., Gerostathis Th., Filippas E., Touboul J., Rey V., 2015, Oscillating hydrofoils as

energy devices operating in waves and currents, 11th European Wave & Tidal Energy Conference (EWTEC2015) Nantes, France.

90. Belibassakis K., 2015, Power absorption by arrays of wave energy converters over variable bottom topography, 11th European Wave & Tidal Energy Conference (EWTEC2015) Nantes, France.

91. Belibassakis K., Filippas E., Touboul J., Rey V., 2015, Hydrodynamic analysis of oscillating hydrofoils in waves and currents, Proc. 16th International Maritime Association of the Mediterranean (IMAM2015), Pula Croatia.

92. Belibassakis K.A., Touboul J., Rey V., 2016, On the modeling of linear waves interacting with bathymetry in the presence of vertically sheared currents , Proc. 26th Intern. Ocean & Polae Engineering Conference (ΙSOPE2016), Rhodes, Greece.

93. Belibassakis K.A., Molin B., Kimmoun O., 2016, Weakly nonlinear transformation of wavegroups over variable bathymetry, Proc. 26th Intern. Ocean & Polae Engineering Conference (ΙSOPE2016), Rhodes, Greece.

94. Papathanasiou T.K., Karperaki A., Belibassakis K.A., 2016, An efficient coupled-mode/FEM numerical method for linear wave propagation over 3D variable bathymetry domains, Proc. 26th Intern.Ocean & Polae Engineering Conference (ΙSOPE2016), Rhodes, Greece.

95. Belibassakis K.A., Xiros N., Politis, G., Filippas, E., Aktosun E., Tsarsitalidis, V., 2016, Identification of Flapper Fin Oscillations for Active Flow Control Applications in Improved Watercraft Propulsion, Proc. 26th Intern.Ocean & Polae Engineering Conference (ΙSOPE2016), Rhodes, Greece.

96. Belibassakis K., Filippas E., Gerostathis Th., 2016, Biomimetic marine energy devices in waves and sheared currents, 2nd International Conference on Renewable Energies Offshore (RENEW2016) 24 - 26 October 2016, Lisbon, Portugal.

97. Belibassakis K., Gerostathis Th., Athanassoulis, G.A., 2016, A 3D-BEM coupled-mode method for WEC arrays in variable bathymetry, 2nd International Conference on Renewable Energies Offshore (RENEW2016) 24 - 26 October 2016, Lisbon, Portugal

C. CONFERENCE PAPERS (reviewed on the basis of abstract)

1. Athanassoulis, A.M. Prospathopoulos and K.A. Belibassakis, 1996, A normal-mode solution for 3D acoustic scattering from a cylindrical island, Proceedings 3rd European Conference on Underwater Acoustics, Heraklion, Greece, (24-28 June 1996).

2. Athanassoulis and K.A. Belibassakis, 1996, Three-dimensional acoustic scattering of a source-generated field from an axisymmetric obstacle of general vertical section in a waveguide, Proceedings 3rd European Conference on Underwater Acoustics, Heraklion, Greece, (24-28 June 1996).

3. The ‘Amfitriti’ group, National Technical University of Athens, 1996, The integrated software AMFITRITI and its application to the calculation of Transmission Losses in the Aegean Sea environment, Proceedings of the Intern. Conference Circuits, Systems and Computers 96, Piraeus, Greece, July 1996.

4. Belibassakis, K.A., Prospathopoulos, I.M., Voutsinas, S.G., Numerical modelling of noise propagation in the atmospheric environment and application to wind energy installation, Proceedings of European Wind Energy Conference, EWEC’97, Ireland October 1997.

5. Athanassoulis, G.A., Belibassakis, K.A., Development and study of the Green’s function for water waves over variable bathymetry domains, Intern. Symposium WAVES’98, Ocean Wave Kinematics, Dynamics and Loads on Structures, American Society of Civil Engineers, Houston Texas, April 1998.

6. Athanassoulis, G.A., Belibassakis, K.A., Livaditi, E.L., An enhanced coupled-mode theory for sound propagation over an arbitrary bottom topography, 4th European Conference on Underwater Acoustics ECUA’98, Rome, Italy, September 1998.

7. Prospathopoulos, I.M., Belibassakis, K.A., Voutsinas, S.G., 1999, Numerical modelling of propagation of noise emitted from wind parks, Proceedings of European Wind Energy Conference, EWEC 99, Nice, France March 1999.

8. Athanassoulis, G.A., Belibassakis, K.A., Gerostathis, Th., 2000, A coupled-mode theory for the scattering of acoustic waves from localized 3D scatterers superimposed over a parallel contour bathymetry , 5th European Conference on Underwater Acoustics, Lyon 2000

9. Athanassoulis, G.A., Belibassakis, K.A., 2000, Nonlinear water wave problems over a general bathymetry: A unified theory, Proceedings of “Rogue Waves 2000”, organised by IFREMER, Brest, France

10.Athanassoulis, G.A., Belibassakis, K.A., 2001, Nonlinear water wave problems over a general bathymetry: A unified variational approach, Proceedings of the Intern. Conference Progress in Nonlinear Science, Nizhny Novgorod, Russia.

11.Athanassoulis, G.A., Belibassakis, K.A., Kanellopoulos, J., 2002, A coupled-mode model for the

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solution to the time-harmonic Maxwell's equations in a curved waveguide of rectangular cross section, 2nd European Symposium Numerical Methods in Electromagnetics, JEE’2002, Toulouse 2002.

12.Athanassoulis, G.A., Belibassakis, K.A., 2002, A consistent coupled-mode theory for underwater sound propagation in a general, stratified acoustic environment, 6th European Conference on Underwater Acoustics, Gdansk 2002.

13.Athanassoulis, G.A., Belibassakis, K.A., Dougalis, V. A., Kampanis N.A and D. A. Mitsoudis, 2002, Simulation of underwater sound propagation in a general stratified environment by a coupled mode and a finite element method, Forum Acusticum, 3rd European Congress on Acoustics, European Acoustics Association, Sevilla 2002

14.Athanassoulis, G.A., Belibassakis, K.A., 2002, A coupled-mode theory for underwater sound propagation in a stratified environment. Comparison of results and validation vs. a finite element method, ACOUSTICS 2002, Hellenic Institute of Acoustics, Patras University, September 2002.

15. Barstow S, Mørk G, Lasse Lønseth, Peter Schjølberg, Gerassimos Athanassoulis, Kostas Belibassakis, Theodore Gerostathis and Gerard Spaan, 2003, WORLDWAVES: High quality coastal and offshore wave data within minutes for any global site, COPEDEC VΙ, 2003 Colombo, Sri Lanka, September 2003.

16. Steve Barstow, Gunnar Mørk, Lasse Lønseth, Peter Schjølberg, Ulla B. Machado, Gerassimos Athanassoulis, Kostas Belibassakis, Theodore Gerostathis and Gerard Spaan, 2003, WORLDWAVES: High quality coastal and offshore wave data within minutes for any global site, Coasts and Ports 2003, Auckland, New Zealand.

17. Athanassoulis, G.A., Belibassakis, K.A., Gerostathis, Th., 2006, Long-term wind and wave data for Port & Harbour Engineering: Exploiting existing offshore data and numerical models to get a timely, site-specific nearshore analysis, 5th Hellenic Conference of Port Engineering, Athens November 2006 (in Greek).

18. Belibassakis, K.A., Gerostathis, T., Athanassoulis, G.A., 2008, Wave-current-seabed interaction over general bottom topography, Coastal Technology Workshop, COAST2008, 29-30 May 2008, Trondheim Norway.

19. Athanassoulis, G.A., Belibassakis, K.A., Gerostathis, T., 2013, Offshore to nearshore wave spectrum transformation, taking into account wave – current – seabed interaction. 2012 Intern. Conference on Advances in Coupled Systems Mechanics (ACEM'12), Seoul, Korea.

20. Belibassakis K., Filippas E., 2014, Biomimetic flapping foil thrusters for augmenting ship propulsion in waves, Proc. Hellenic Institute of Marine Technology 2014 (in Greek).

21. Karperaki A., Belibassakis K.A., Papathanasiou T.K., 2015, Propagation of acoustic-gravit wavs in inhomogeneous ocean environment generated by sea-bottom deformation, Proc. 8th GRACM International Congress on Computational Mechanics GRACM 2015 Volos, 12 July – 15 July 2015, Greece.

22. Belibassakis K.A., 2015, Marine propulsion in waves by flapping foil systems, Proc. 8th GRACM International Congress on Computational Mechanics GRACM 2015 Volos, 12 July – 15 July 2015, Greece.

23. Belibassakis K., Filippas E., Gerostathis Th., 2016, Biomimetic Systems Operating as Marine Energy Devices in Waves and Sheared Currents, 11th HSTAM Intern. Congress on Mechanics, 27-30 May 2016, Athens.

24. Belibassakis K., Gerostathis Th., Athanassoulis, G.A., 2016, Performance of Arrays of Wave Energy Converters Operating in Variable Bathymetry Regions, 11th HSTAM Intern. Congress on Mechanics, 27-30 May 2016, Athens.

25. Karperaki A., Papathanasiou T.K., Belibassakis K.A., 2016, A Coupled-Mode System for the Near-Trapping of Water Waves in the Presence of Variable Bathymetry, 11th HSTAM Intern. Congress on Mechanics, 27-30 May 2016, Athens.

26. Lampropoulos N., Koubogiannis, D., Belibassakis K., 2016, Numerical Simulation of Flapping Foil Propulsion, 11th HSTAM Intern. Congress on Mechanics, 27-30 May 2016, Athens.

D. POSTER PRESENTATIONS

1. Johnsen H., Kallos G., Krogstad H., Athanassoulis G., Barstow S., Heiberg H., Carretero J.C., Chapron B., Queffeulou P., Morales G., Emmanouil G., Galanis G., Gerostathis T.P., Belibassakis K.A., Stefanakos C.N., Croize-Fillon D, 2005, Development and Application of Validated Geophysical Ocean Wave Products from ENVISAT ASAR and RA-2 Instruments παρουσιάσθηκε ως Poster στο 4th EuroGOOS Conference EuroGoos'2005, Brest June 2005, France, και στο WAVES'2005, Madrit July 2005, Spain.

2. Papathanasiou Th, Karperaki, A., Theotokoglou E., Belibassakis,K. 2014, Hydroelastic analysis of ice shelves under long wave excitation, EGU 2014-819.

3. Touboul, J., Belibassakis K., Rey V. 2015, 2D Propagation of Water Waves in the Presence of

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Vorticity, EGU2015-3592. 4. Laffitte E., Belibassakis K., Bruno S., Rey V., Touboul J., 2016, Influence of a constant vorticity on

the Bragg resonance phenomenon Vol. 18, EGU2016-8228. E. CHAPTERS IN BOOKS & COMMITTEE REPORTS

1. Kaklis P.D., Politis C.G., Belibassakis K.A., Ginnis A.I., Kostas K.V., Gerostathis Th.P., 2016, Boundary-Element Methods and Wave Loading on Ships, to appear in the second edition of the Encyclopedia of Computational Mechanics. Edited by Erwin Stein, Rene de Borst and Thomas J.R. Hughes.

2. Tedeschi R. (chairman), Athanassoulis, G.A., Boonstra, H., Brok,A.K., Cardone, A.J., Daley, C., Haver, S., Hrayama, T., Kujala, P., Litonov, O., Olagnon, M., Schlacter, G. (members), and Belibassakis, K. (associate), 1997, Report of Committee I.1: Environment, T. Moan & S. Berge (Eds) Proceedings of the 13th International Ship and Offshore Structure Congress (ISSC), Cambridge, Pergamon, Vol. 1, pp. 1-58.

F. TECHNICAL REPORTS

Author or co-author to number of Technical Reports. An indicative list is provided below:

Politis G. Belibassakis K., 1987, Analytical design of marine propellers using higher-order panel methods, Final Report of Research Project, NAME-NTUA (in Greek).

Belibassakis K., 1988, Prediction of unsteady marine propeller performance by vortex lattice method Report NAME-NTUA (in Greek).

Politis G. Belibassakis K., 1989, Performance of controllable pitch marine propellers using boundary element method, Final Report of Research Project, NAME-NTUA (in Greek).

Politis G. Belibassakis K., 1990, Performance of controllable pitch marine propellers using boundary element method – Experimental verification and optimization, Final Report of Research Project, NAME-NTUA (in Greek).

Belibassakis K., 1992, Unsteady hydrofoil analysis by discrete vortex methods, Report NAME-NTUA (in Greek).

Politis G. Belibassakis K., Triantafyllou Μ., 1998, Development of fish propulsion system, Final Report of Research Project, NAME-NTUA (in Greek).

Belibassakis K., 2000, Vibration of ship propulsion system, Report NAME-NTUA (in Greek).

Belibassakis K., 2007, Prediction methods of waves in marine and coastal environment with application to development of naval technology for the application of novel oil-spill combating technique, Final Report of Research Project ARCHIMEDES, Dept. of Naval Architecture, Technological Educational Institute of Athens. (http://www.na.teiath.gr/research/archimedes_8/publications.html).

Belibassakis K., 2015, Augmenting ship propulsion in rough sea by biomimetic wing system, Final Report of Research Project ARISTEIA-BIOPROPSHIP, School of Naval Architecture & Marine Engineering – National Technical University of Athens (http://arion.naval.ntua.gr/~biopropship/).

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ANALYSIS OF SCIENTIFIC WORKS PHD THESIS: Belibassakis K., 1992, A velocity based Boundary Element Method for the analysis of marine propellers in unsteady flow, Dept. of Naval Architecture & Marine Engineering, National Technical University of Athens. A velocity-based boundary integral equation formulation is presented and studied concerning the exterior Neumann problem for a vector field in R3, using surface vorticity distributions as the boundary unknowns. Using the above system of equations a boundary element technique is developed for the calculation of incompressible, inviscid flow velocity and pressure distributions around arbitrary shaped, three dimensional bodies. A pressure type Kutta condition is satisfied along the trailing edge of the lifting sections. Application of the numerical scheme in cases of isolated bodies and wings, as well as in cases of complex configurations, in steady flow conditions, has shown that accurate results can be obtained with relatively low computational effort. Subsequently, the mathematical formulation of the inviscid flow problem concerning the operation of marine propellers In unsteady flow conditions is presented and the treatment of the problem, under the weak interaction assumption between the propeller and the sheared onset flow, in the framework of potential, lifting flow applications is investigated. A boundary integral equation (Fredholm type, second kind) technique, involving surface vorticity distributions as the boundary unknowns, is developed for the solution of the Neumann boundary value problem regarding vector fields in R3. Subsequently, the method is applied to the calculation of incompressible, irrotational, inviscid flow velocity and pressure distributions around arbitrarily shaped three dimensional bodies. In the case of lifting bodies, a pressure type Kutta condition along the trailing edge is satisfied. Application of the developed numerical scheme in the case of wings and bodies in steady flow conditions, possessing either analytical or datum solution, has shown that accurate results with relatively low computational effort can be obtained. A particular application concerning the steady and unsteady marine propeller performance problems is presented. The modelling includes hub, cone and finite blade thickness effects. A comparison between the results obtained by the present method, other established boundary element methods from the relevant literature and experimental measurements is given and the identified discrepancies are discussed. Capable to treat the rotational terms of the velocity field, assosiated with spatial vorticity distributions, the present formulation may found useful in the numerical representation of the kinematics of the general flow. Results have been published in journal papers (α.2, α.5, α.9), ans also have been presented in international conferences and published in the corresponding proceedings (papers b.2, b.3, b.11). DIPLOMA THESIS: Belibassakis K., 1992, Application of panel methods to marine propeller design, Dept. of Naval Architecture & Marine Engineering National Technical University of Athens. The thesis focuses on the design problem for a marine propeller and its numerical treatment using second-order cight-nodc quadrilateral panels. An extensive sensitivity analysis is presented showing that sufficiently exact solutions of the design problem can be obtained with a small number of panels. Comparison of the panel method with the vortex lattice method for a samplc of design cases shows systematic differences in the calculated pitch distributions and propeller thrust and torque characteristics with trends confirmed by practical design experience. Since computer space and time requirements tor the two methods arc comparable the pancl method approach seems to be a preferable alternative for marine propeller design. Results have been presented in conference paper (b.1). CHAPTERS IN BOOKS Kaklis P.D., Politis C.G., Belibassakis K.A., Ginnis A.I., Kostas K.V., Gerostathis Th.P., 2016, Boundary-Element Methods and Wave Loading on Ships, to appear in the second edition of the Encyclopedia of Computational Mechanics. Edited by Erwin Stein, Rene de Borst and Thomas J.R. Hughes. The hydrodynamic problem of a ship moving with constant forward speed while undergoing small-amplitude oscillatory motions about its mean steady-state position, is modeled as a Boundary-Integral-Equation (BIE) involving surface distributions of the fundamental solution of Laplace's equation and its derivatives and alternative Green functions. The chapter reviews the various low- and higher-order Boundary-Element-Methods (BEM), developed for the numerical solution of these BIEs via collocation or Galerkin techniques involving finite-dimensional bases for representing the involved geometric configuration and approximating the unknown physical quantities. Then, we focus on presenting and discussing recent experience gained from embedding BEM into Iso-Geometric Analysis (IGA) for the linear wave-resistance problem. Two IGA-BEM solvers, based on NURBS and T-spline representations of

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the ship hull, are presented and compared for the so-called Neumann-Kelvin formulation of this problem. The local refinement capabilities of the adopted T-spline representation of the ship geometry leads to a solver with higher accuracy and efficiency as compared to the corresponding NURBS based solver. Furthermore, the developed hydrodynamic solvers, along with the corresponding ship-parametric models, are integrated within an optimization environment which is tested in two optimization problems. The first problem, of local optimization character, focuses on the optimization of the bulbous shape of a container ship against the criterion of minimum wave resistance. The second case performs a global hull-shape optimization of a container ship targeting the minimization of both the total resistance and the deviation from a target deadweight. The chapter ends with a brief discussion for further research towards broadening the coverage of IGA-BEM methods in application areas related to ship wave loads. A. JOURNAL PAPERS a.1 Athanassoulis, G.A., Skarsoulis, E.K., Belibassakis, K.A., 1994, Bivariate Distributions with Given Marginals with an Application to Wave Climate Description, Applied Ocean Research, Vol.16, pp. 1-17. The class of bivariate probability distributions with given (prespecitied) marginals is studied, and a special member of this class, the Plackett model, is applied to represent the joint probability distribution of significant wave height (Hs) and mean zero-uperossing period (To2). The distinctive features of the bivariate Plackett model are: (i) it accepts any kind of univariate probability models as marginals, (ii) it can accurately model the degree of correlation between Hs and To2, and (iii) it permits an easy and reliable estimation of parameters. Applications of the Plackett model to the description of (Hs, To2) statistics for certain sea locations illustrate its overall performance and flexibility. The possibility of extending this approach to the multivariatecase is discussed. a.2 Belibasakis, K.A., Politis G.K., 1995, A Boundary Integral Equation Formulation of the Neumann Problem for a Vector Field in R3 with Application to Potential Lifting Flows, Engineering Analysis with Boundary Elements, Vol.16, pp.5-17. A velocity-based boundary element technique is presented for the calculation of incompressible, inviscid flow velocity and pressure distributions around arbitrary shaped, three dimensional bodies. The method is based on a boundary integral equation formulation of the exterior Neumann problem for a vector field in R3, which involves surface vorticity distributions as the boundary unknowns. A pressure type Kutta condition is satisfied along the trailing edge of the lifting sections. Application of the numerical scheme in cases of isolated bodies and wings, as well as in cases of complex configurations, in steady flow conditions, has shown that accurate results can be obtained with relatively low computational effort. Capable of treating the terms of the velocity field associated with the spatial vorticity and rate of expansion distributions, the present formulation may find useful applications in the numerical representation of the kinematics of a general flow problem. a.3 Athanassoulis, G.A., Belibassakis, Κ.Α., 1997, All-frequency normal-mode solution of the 3D acoustic scattering from a vertical cylinder in a plane horizontal waveguide, Journal of the Acoustical Society of America, Vol. 101, pp. 3371-3384. The three-dimensional acoustic scattering from a vertical, impenetrable cylinder in a waveguide is studied. The analytical solution of the problem, for a Dirichlet or a Neumann boundary condition on the scatterer, has been derived recently by Athanassoulis and Prospathopoulos J. Acoust. Soc. Am. 100, 206–218, 1996 in the form of a double-infinite normal-mode series, representing the total acoustic field. In order to extend the applicability of this solution to higher frequencies, the total field is decomposed into the incident and the scattered parts. A series expansion for the scattered field is obtained, and the critical parameter controlling its azimuthal convergence is shown to be the nondimensional wave number ka based on the radius a of the cylinder. The general term of the series starts to decay exponentially immediately after the azimuthal index has exceeded the critical value ka, a fact justifying the introduction of the concept of azimuthal-evanescent modes. By exploiting the above decomposition, the direct numerical summation of the normal-mode series becomes feasible up to ka~1000. For calculations at even higher frequencies (ka→∞ ), asymptotic expressions are derived by using appropriate integral representations of Bessel and Hankel functions, in conjunction with the method of stationary phase. The asymptotic analysis shows that the scattered field is obtained as a superposition of 2-D point sources lying on the boundary of the vertical cylinder, with appropriate

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amplitudes and phases. Excellent agreement between asymptotic and direct summation numerical results has been demonstrated, at moderate frequencies, where both representations are expected to be valid. a.4 Loukakis, Th, Bardis, L.,., Belibassakis, K., et al, 1997, A computer aided ship design system, Techn. Chron. Sci. J., TCG, Vol. 17, No.1. This paper present a computer aided ship design system, capable of performing the design of a small or medium sized vessel in a simple and quick way, while providing reliable results. The basic operations of the system include production and fairing of hull lines for planning vessels with chine and semi-displacements round bottom vessels, performance of all pertinent ydrostatic calculations, resistance prediction using appropriate systematic series, prediction of propulsion characteristics and selection of main engine and reduction gear, selection of the appropriate propeller from systematic series, design of internal arrangement of the vessel, performance of all necessary strength calculations, considering that the boat is built from composite materials and seakeeping performance assessment for these vessels. During the design procedure, all input or calculated data are stored in a data base, something that provides the user with the possibility to have always at his disposal a complete view of the study, at any stage. a.5 Belibasakis, K.A. Politis, G.K., 1998, A Non-Linear Velocity Based Boundary Element Method for the Analysis of Marine Propellers in Unsteady Flow, International Shipbuilding Progress, Vol. 45, pp. 93-133. The mathematical formulation of the inviscid flow problem concerning the operation of marine propellers in unsteady flow conditions is presented and the treatment of the problem, under the assumption of weak interaction between the propeller and the sheared onset flow, in the framework of potential, lifting flow applications is investigated. A boundary integral (Fredholm type, second kind) technique, involving surface vorticity distributions as the boundary unknowns, is applied to model the steady and unsteady marine propeller performance problems. A pressure-type Kutta condition is satisfied along the trailing edge of the blades. The modeling includes hub and finite blade thickness effects. A comparison between the present method, other boundary element techniques and experimental results is given and discussed. Capable to treat the terms of the velocity field associated with spatial vorticity distributions, the present formulation, in conjunction with solvers of the vorticity transport equation, can be utilized to model the unsteady propeller analysis problem, in order to overcome the limitations of weak interaction assumption. a.6 Athanassoulis, G.A., Belibassakis, K.A., 1999, A consistent coupled-mode theory for the propagation of small-amplitude water waves over variable bathymetry regions, Journal of Fluid Mechanics, Vol. 389, pp. 275-301. Extended mild-slope equations for the propagation of small-amplitude water waves over variable bathymetry regions, recently proposed by Massel (1993) and Porter & Staziker (1995), are shown to exhibit an inconsistency concerning the sloping-bottom boundary condition, which renders them non-conservative with respect to wave energy. In the present work, a consistent coupled-mode theory is derived from a variational formulation of the complete linear problem, by representing the vertical distribution of the wave potential as a uniformly convergent series of local vertical modes at each horizontal position. This series consists of the vertical eigenfunctions associated with the propagating and all evanescent modes and, when the slope of the bottom is different from zero, an additional mode, carrying information about the bottom slope. The coupled-mode system obtained in this way contains an additional equation, as well as additional interaction terms in all other equations, and reduces to the previous extended mild-slope equations when the additional mode is neglected. Extensive numerical results demonstrate that the present model leads to the exact satisfaction of the bottom boundary condition and, thus, it is energy conservative. Moreover, it is numerically shown that the rate of decay of the modal-amplitude functions is improved from O(n−2), where n is the mode number, to O(n−4), when the additional sloping-bottom mode is included in the representation. This fact substantially accelerates the convergence of the modal series and ensures the uniform convergence of the velocity field up to and including the boundaries.

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a.7 Belibassakis, K.A., 2000, The Green’s function of the mild-slope equation, Wave Motion, Vol.32, pp. 339-361. In the present work the Green’s function of the mild-slope and the modified mild-slope equations is studied. An effective numerical Fourier inversion scheme has been developed and applied to the construction and study of the source-generated water-wave potential over an uneven bottom profile with different depths at infinity. In this sense, the present work is a prerequisite to the study of the diffraction of water waves by localized bed irregularities superimposed over an uneven bottom. In the case of a monotonic bed profile, the main characteristics of the far-field are: (i) the formation of a shadow zone with an ever expanding width, which is located along the bottom irregularity, and (ii) in each of the two sectors not including the bottom irregularity the asymptotic behavior of the wave field approaches the form of an outgoing cylindrical wave, propagating with an amplitude of order O(R−1/2), where R is the distance from the source, and wavelength corresponding to the sector-depth at infinity. Moreover, the weak wave system propagating in the shadow zone is of order O(R−3/2), and along the bottom irregularity consists of the superposition of two outgoing waves with wavelengths corresponding to the two depths at infinity. a.8 Belibassakis, K.A., Athanassoulis, G.A., Gerostathis, Th., 2001, A coupled-mode system for the refraction-diffraction of linear waves over steep three dimensional topography, Applied Ocean Research, Vol. 23, pp. 319-336. A consistent coupled-mode model, recently developed by Athanassoulis and Belibassakis (1999), is generalized in 2+1 dimensions and applied to the diffraction of small-amplitude water waves from localized three-dimensional scatterers lying over a parallel-contour bathymetry. The wave field is decomposed into an incident field, carrying out the effects of the background bathymetry, and a diffraction field, with forcing restricted on the surface of the localized scatterer(s). The vertical distribution of the wave potential is represented by a uniformly convergent local-mode series containing, except of the usual propagating and evanescent modes, an additional mode, accounting for the sloping bottom boundary condition. By applying a variational principle, the problem is reduced to a coupled-mode system of differential equations in the horizontal space. To treat the unbounded domain, the Berenger Perfectly Matched Layer model is optimized and used as an absorbing boundary condition. Computed results are compared with other simpler models and verified against experimental data. The inclusion of the sloping-bottom mode in the representation substantially accelerates its convergence, and thus, a few modes are enough to obtain accurately the wave potential and velocity up to and including the boundaries, even in steep bathymetry regions. The present method provides high-quality information concerning the pressure and the tangential velocity at the bottom, useful for the study of oscillating bottom boundary layer, sea-bed movement and sediment transport studies. a.9 Belibassakis, K.A., Politis G.K., 2002, Analysis of unsteady propeller performance by a surface vorticity panel method, Schiffstechnik-Ship Technology Research, Vol. 49, pp.13-21. Reliable information concerning both the blade pressure distributions and the unsteady integrated propeller characteristics can be obtained employing potential theory. In this work we treat the unsteady propeller analysis problem using potential flow theory under the assumption of weak interaction between the propeller and the sheared onset flow using as unknowns in the boundary integral equations the tangential components of the vector field on the boundary. Because of the close relationship of this surface singularity distribution with the notion of vortex sheets, we call this a surface vorticity distribution. The proposed method could support detailed design of propellers. Although the present application is restricted to irrotational flow, the surface vorticity method can be used in conjunction with solvers of the vorticity transport equation for inviscid flows or solvers of the three-dimensional Euler equations to improve the numerical unsteady propeller analysis and the determination of the effective wake. a.10 Athanassoulis, G.A., Belibassakis, K.A., Gerostathis, Th., 2002, The POSEIDON nearshore wave model and its application to the prediction of the wave conditions in the nearshore/coastal region of the Greek Seas, Global Atmosphere and Ocean System (GAOS), Vol 8 (2-3), 101-117. In the present work, the Poseidon Nearshore Wave Model (PNWM) developed in the framework of the POSEIDON project1, and its application to the prediction of the wave conditions in nearshore/coastal regions of Greek seas is presented. The PNWM is based on a one-way energy coupling between a third-generation, phase-averaged, nearshore wave model and a local phase-resolving model, nested in the

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first model. The local wave model is supported by the consistent coupled-mode theory, based on an enhanced local-mode representation of the wave velocity field, which except for the propagating and the evanescent modes includes an additional mode, permitting the exact satisfaction of the sloping-bottom boundary condition, even in areas with locally steep bottom slope and large curvature. Thus, three-dimensional diffraction effects are fully treated in the local nested area. Numerical results are presented demonstrating the application of the PNWM to nearshore and coastal sites of the Greek seas. a.11 Belibassakis, K.A., Athanassoulis, G.A., 2002, Extension of second-order Stokes theory to variable bathymetry, Journal of Fluid Mechanics, Vol. 464, pp. 35-80. In the present work the second-order Stokes theory has been extended to the case of a generally-shaped bottom profile connecting two half-strips of constant (but possibly different) depths, initiating a method for generalizing the Stokes hierarchy of second and higher order wave theory, without the assumption of spatial periodicity. In modeling the wave-bottom interaction three partial problems arise: the first-order, the unsteady second-order and the steady second-order ones. The three problems are solved by using appropriate extensions of the consistent coupled-mode theory developed by the same authors (Athanassoulis & Belibassakis, 1999) for the linearised problem. Apart from the Stokes small-amplitude expansibility assumption, no additional asymptotic assumptions have been introduced. Thus, bottom slope and curvature may be arbitrary, provided that the resulting wave dynamics is Stokes compatible. Accordingly, the present theory can be used for the study of various wave phenomena (propagation, reflection, diffraction) arising from the interaction of weakly non-linear waves with a general bottom topography, in intermediate water depth. An interesting phenomenon, that is also very naturally resolved, is the net-mass flux induced by the depth variation, which is consistently calculated by means of the steady second-order potential. The present method has been validated against experimental results and fully nonlinear numerical solutions. It has been found that it correctly predicts the second-order harmonic generation, the amplitude non-linearity, and the amplitude variation due to non-resonant first-and-second harmonic interaction, up to the point where the energy transfer to the third and higher harmonics cannot be neglected anymore. Under the restriction of weak non-linearity, the present model can be extended to treat obliquely incident waves and the resulting second-order refraction patterns, and to study bichromatic and/or bi-directional wave-wave interactions, with application to the transformation of second-order random seas in variable bathymetry regions. a.12 Athanassoulis, G.A., Belibassakis, K.A., 2002, Probabilistic description of metocean parameters by means of kernel density models. Part 1: Theoretical background and first results, Applied Ocean Research, Vol. 24, pp.1-20. In the present work a general Kernel Density Model (KDM) has been introduced and assessed for the analytic representation of any empirical distribution function (univariate or multivariate) of metocean parameters. This model is based on the concept of kernel density function, which has been first introduced in the context of nonparametric discriminant analysis by by Fix and Hodges [Nonparametric discrimination: consistency properties, 1951], and generalised to the multivariate case by Cacoulos [Ann Inst Math 18 (1966) 178]. In its standard form, the Kernel Density Estimators are applied to given samples of observations, producing analytical (yet nonparametric) estimations of the unknown (underlying) probability density functions. Motivated by the fact that, in many practical applications, metocean data are available only in the form of histograms (grouped data), the present KDM is implemented in a way permitting to obtain analytical estimates of the underlying probability distributions on the basis of grouped data. The main features of the proposed KDM are: (i) it can treat multivariate data with very reasonable computational cost, (ii) it is flexible enough to represent quite general distribution patterns both in the univariate and in the multivariate case, (iii) with an appropriate selection of the bandwidth, results in very satisfactory representations, avoiding local pathologies, (iv) it is marginally consistent, i.e. any marginal distribution calculated by integration from the multivariate model is identical with the corresponding marginal KDM, obtained directly from the marginal data. First numerical results are presented herein, showing that the performance of the present model is very satisfactory for all the wave parameters studied, univariate, bivariate, the trivariate (Hm,Tm,Θm), and conditionals. A more detailed investigation, including also applications to other metocean parameters, will be presented as a second part. a.13 Belibassakis, K.A., 2003, A coupled-mode technique for the transformation of ship-generated waves over variable bathymetry regions, Applied Ocean Research, Vol. 25, pp.321-336.

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In the present work, a coupled-mode technique is applied to the transformation of ship’s waves over variable bathymetry regions, characterised by parallel depth-contours, without any mild-slope assumption. This method can be used, in conjunction with ship’s near-field wave data in deep water or in constant-depth, as obtained by the application of modern (linearised or non-linear) ship computational fluid dynamic (CFD) codes, or experimental measurements, to support the study of wave wash generated by fast ships and its effects on the nearshore/coastal environment. Under the assumption that the ship’s track is straight and parallel to the depth-contours, and relatively far from the bottom irregularity, the problem of propagation–refraction–diffraction of ship-generated waves in a coastal environment is efficiently treated in the frequency domain, by applying the consistent coupled-mode model developed by Athanassoulis and Belibassakis [J. Fluid Mech. 1999;389] to the calculation of the transfer function enabling the pointwise transformation of ship-wave spectra over the variable bathymetry region. Numerical results are presented for simplified ship-wave systems, obtained by the superposition of source–sink Havelock singularities simulating the basic features of the ship’s wave pattern. The spatial evolution of the ship-wave system is examined over a smooth but steep shoal, resembling coastal environments, both in the subcritical and in the supercritical case. Since any ship free-wave system, either in deep water or in finite depth, can be adequately modelled by wavecut analysis and suitable distribution of Havelock singularities e.g. as presented by Scrags [21st Int. Conf. Offshore Mech. Arctic Eng., OMAE2002, Oslo, Norway, June 2002], the present method, in conjunction with ship CFD codes, supports the prediction of ship wash and its impact on coastal areas, including the effects of steep sloping-bed parts. a.14 Belibassakis, K.A., Athanassoulis, G.A., 2004, Three-dimensional Green's function of harmonic water-waves over a bottom topography with different depths at infinity, Journal of Fluid Mechanics, Vol. 510, pp.267-302. The three-dimensional Green’s function of water waves in variable bathymetry regions, associated with the problem of propagation of water waves emitted from a monochromatic point source, is derived and studied. The solution is of interest in its own right but also provides useful information for the formulation and treatment of complex wave-body-seabed interaction problems in variable bathymetry regions, especially as regards the hydrodynamic characteristics of large structures installed in the nearshore and coastal environment. Assuming a parallel-contour bathymetry, with a continuous depth function of the form h(x,y)=h(x), attaining constant, but possibly different, values at the semi-infinite regions x<a and x>b, the problem is reduced to a two-dimensional one, by using Fourier transform. The transformed problem is treated by applying domain decomposition and reformulating it as a transmission problem in the finite domain containing the bottom irregularity. An appropriate decomposition of the wave potential is introduced, permitting to solve analytically the singular part, and to reformulate the problem for the regular part as a variational problem. An enhanced local-mode series representation is used for the regular wave potential in the variable bathymetry region, including the propagating mode, the sloping-bottom mode [see Athanassoulis & Belibassakis (1999)], and a number of evanescent modes. Using this representation, in conjunction with the variational principle, a forced system of horizontal coupled-mode equations is derived for the determination of the complex modal-amplitude functions of the regular wave potential. This system is numerically solved by using a second-order, central, finite-difference scheme. The source-generated water-wave potential is, finally, obtained by an efficient numerical Fourier inversion based on FFT. Numerical results are presented and discussed for various bottom topographies, including smooth but steep underwater trenches and ridges, putting emphasis on the identification of the important features of the near- and far-field patterns on the horizontal plane and on the vertical plane containing the point source. Characteristic patterns of trapped (well localised) wave propagation over ridges have been predicted and discussed. a.15 Belibassakis, K.A., Athanassoulis, G.A., 2005, A coupled-mode model for the hydroelastic analysis of large floating bodies over variable bathymetry regions, Journal of Fluid Mechanics Vol. 531, pp.221-249. The consistent coupled-mode theory (Athanassoulis & Belibassakis 1999) is extended and applied to the hydroelastic analysis of large floating bodies of shallow draft or ice sheets of small and uniform thickness, lying over variable bathymetry regions. A parallel-contour bathymetry is assumed, characterised by a continuous depth function of the form h(x,y)=h(x), attaining constant, but possibly different, values at the semi-infinite regions x<a and x>b. We consider the scattering problem of harmonic, obliquely-incident, surface waves, under the combined effects of variable bathymetry and a

floating elastic plate, extending from x=a to x=b x a= and -∞<y<∞. Under the assumption of small-

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amplitude incident waves and small plate deflections, the hydroelastic problem is formulated within the context of linearised water-wave and thin elastic-plate theory. The problem is reformulated as a transition problem in a bounded domain, for which an equivalent, Luke-type (unconstrained), variational principle is given. In order to consistently treat the wave field beneath the elastic floating plate, down to the sloping bottom boundary, a complete, local, hydroelastic-mode series expansion of the wave field is used, enhanced by an appropriate sloping-bottom mode. The latter enables the consistent satisfaction of the Neumann bottom-boundary condition on a general topography. By introducing this expansion into the variational principle, an equivalent coupled-mode system of horizontal equations in the plate region (a≤x≤b) is derived. Boundary conditions are also provided by the variational principle, ensuring the complete matching of the wave field at the vertical interfaces (x=a and x=b), and the requirements that the edges of the plate are free of moment and shear force. Numerical results concerning floating structures lying over flat, shoaling and corrugated seabeds are comparatively presented and the effects of wave direction, bottom slope and bottom corrugations on the hydroelastic response are presented and discussed. The present method can be easily extended to the fully 3D hydroelastic problem, including bodies or structures characterized by variable thickness (draught), flexural rigidity and mass distributions. a.16 Belibassakis, K.A., Athanassoulis, G.A., 2006, A coupled-mode technique for weakly non-linear wave interaction with large floating structures lying over variable bathymetry regions Applied Ocean Research Vol.28, 59-76. A coupled-mode method is developed and applied to hydroelastic analysis of large floating platforms of shallow draft, lying over variable bathymetry regions, characterised by parallel bottom contours. We consider the scattering problem of surface waves, under the combined effects of variable bathymetry and a semi-infinite floating elastic plate, in the time domain. The present development is based on appropriate generalisation of Luke’s (1967) unconstrained variational principle, which models the evolution of nonlinear water waves in intermediate water depth over a general bathymetry. Assuming small plate deflections and neglecting the rotation of plate section, the large floating structure has been modelled as a thin elastic plate. The present approach is based on appropriate extensions of the nonlinear coupled-mode model developed by Athanassoulis and Belibassakis [A nonlinear coupled-mode model or water waves over a general bathymetry. In: Proc. 21st international conference on offshore mechanics and arctic engineering OMAE 2002] for waves propagating in variable bathymetry regions. In order to consistently treat the wave field beneath the elastic floating plate, down to the sloping bottom boundary, a complete, local-mode series expansion of the wave field is used, enhanced by appropriate sloping-bottom and free-surface modes. The latter enable the consistent satisfaction of the Neumann bottom-boundary condition on a general topography, as well as the kinematical conditions on the free surface and on the elastic plate surface. By introducing this expansion into the variational principle, an equivalent coupled-mode system of horizontal equations is derived, fully accounting for the effects of non-linearity and dispersion. Boundary conditions are also provided by the variational principle, ensuring that the edges of the plate are free of moment and shear force. Numerical results concerning floating structures lying over sloping seabeds are presented, as obtained by simplifying the fully nonlinear coupled-mode system keeping only up to second-order terms. The present method can be extended to treat large floating elastic bodies or structures characterised by variable thickness (draft), flexural rigidity and mass distributions. a.17 Magne, R., Belibassakis, K., Herbers, T., Ardhuin, F., O'Reilly, Rey, V. 2007, Evolution of surface gravity waves over a submarine canyon, Journal of Geophysical Research (JGR Oceans), Vol.112, C01002, doi:10.1029/2005JC003035. The effects of a submarine canyon on the propagation of ocean surface waves are examined with a three-dimensional coupled-mode model for wave propagation over steep topography. Whereas the classical geometrical optics approximation predicts an abrupt transition from complete transmission at small incidence angles to no transmission at large angles, the full model predicts a more gradual transition with partial reflection/transmission that is sensitive to the canyon geometry and controlled by evanescent modes for small incidence angles and relatively short waves. Model results for large incidence angles are compared with data from directional wave buoys deployed around the rim and over Scripps Canyon, near San Diego, California, during the Nearshore Canyon Experiment (NCEX). Wave heights are observed to decay across the canyon by about a factor 5 over a distance shorter than a wavelength. However, a spectral refraction model predicts an even larger reduction by about a factor 10, because low-frequency components cannot cross the canyon in the geometrical optics approximation. The coupled-mode model yields accurate results over and behind the canyon. These

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results show that although most of the wave energy is refractively trapped on the offshore rim of the canyon, a small fraction of the wave energy ‘tunnels’ across the canyon. Simplifications of the model that reduce it to the standard and modified mild slope equations also yield good results, confirming that evanescent modes and high-order bottom slope effects are of minor importance for the energy transformation of waves propagating across depth contours at large oblique angles. a.18 Belibassakis, K.A., 2007, A coupled-mode model for the scattering of water waves by shearing currents in variable bathymetry, J. Fluid Mech. Vol. 578, 413-434. A coupled-mode model is presented for wave-current-seabed interaction, with application to the problem of wave scattering by ambient shearing currents in variable bathymetry regions. We consider obliquely incident waves on a horizontally non-homogeneous current in a variable-depth strip, which is characterized by straight and parallel bottom contours. The flow associated with the current is assumed to be directed along the bottom contours and it is considered to be steady and known. In a finite subregion containing the bottom irregularity, we assume that the current has an arbitrary horizontal structure. Outside this region, the current is assumed to be uniform (or zero). Based on a variational principle, in conjunction with a rapidly-convergent local-mode series expansion of the wave pressure field in a finite subregion containing the current variation and the bottom irregularity, a new coupled-mode system of equations is obtained, governing the scattering of waves in the presence of variable bathymetry and longshore shearing currents. By keeping only the propagating mode in the local-mode series, a new one-equation model is derived, having the property to reduce to modified mild-slope equation (Massel 1993, Chamberlain & Porter 1995), when the current is zero, and to the enhanced mild-shear equation (McKee 1996), when the bottom is flat. An important aspect of the present model is that it can be further elaborated to treat shearing currents with general, depth-dependent vertical structure, and to include the effects of weak nonlinearity. a.19 Athanassoulis, G.A., Belibassakis, K.A., 2007, A coupled-mode method for non-linear water waves in general bathymetry with application to steady travelling solutions in constant, but arbitrary, depth, Journal Discrete and Continuous Dynamical Systems DCDS-B, pp. 75-84 (special volume of selected papers from 6th Int. Conference on Dynamical Systems and Differential Equations, Poitiers Meeting, June 25-28, 2006). A non-linear coupled-mode system of horizontal equations is derived with the aid of Luke’s (1967) variational principle, which models the evolution of nonlinear water waves in intermediate depth and over a general bathymetry. The vertical structure of the wave field is exactly represented by means of a local-mode series expansion of the wave potential. This series contains the usual propagating and evanescent modes, plus two additional modes, the free-surface mode and the sloping-bottom mode, enabling to consistently treat the non-vertical end-conditions at the free-surface and the bottom boundaries. The system fully accounts for the effects of non-linearity and dispersion. The main features of this approach are the following: (i) various standard models of water-wave propagation are recovered by appropriate simplifications of the coupled-mode system, and (ii) a small number of modes (up to 5) are enough for the precise numerical solution, provided that the two new modes (the free-surface and the sloping-bottom ones) are included in the local-mode series. In the present work, the consistent coupled-mode system is applied to the numerical investigation of families of steady travelling wave solutions in constant depth, corresponding to a wide range of water depths, ranging from intermediate to shallow-water wave conditions. a.20 Gerostathis, Th., Politis, K., Belibassakis, K.A., Athanassoulis, G.Α., 2007, A Wavelet Galerkin technique for the wave-current-seabed interaction in variable bathymetry regions, Bulletin of the Greek Mathematical Society, Vol.54, 167-178. A Wavelet-Galerkin technique is developed and applied to the wave-current-seabed interaction problem, with application to wave scattering by steady currents in variable bathymetry regions. We consider obliquely incident waves on a horizontally nonhomogeneous current in a variable-depth strip, which is characterized by straight and parallel depth-contours. The flow associated with the current is assumed to be parallel to the isobaths and it is considered to be known. In a finite subregion containing the bottom irregularity the horizontal current has a general structure. Outside this region, the current is assumed to be uniform (or zero). The present method is based on an equivalent reformulation of the wave-current-seabed scattering problem as a coupled mode system of horizontal equations, obtained by Belibassakis & Athanassoulis (1999) using a variational principle and a rapidly-convergent local-mode series expansion of the wave field. In this work, a wavelet representation of the horizontal modal amplitudes is introduced. The latter, in conjunction with a Galerkin formulation, leads to an algebraic system of equations for the corresponding wavelet coefficients. The main advantage of the present

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Wavelet-Galerkin method, in comparison with other numerical techniques (e.g. finite differences, FEM etc), is their intrinsic ability to simultaneously resolve the variety of spatial scales, that are present in each modal amplitude, leading finally to a robust and computationally efficient numerical scheme. The present approach can be considered as an extension of the works by Belibassakis & Athanassoulis (2004), Belibassakis (2005) and Smith (1983,1987), and some of its main features are that it can be further elaborated to treat lateral discontinuities (e.g. vertical vortex sheets) and more general vertical current profiles with cross-jet component, and to include the effects of weak nonlinearity. a.21 Cavaleri, L, et al (2007), Wave modeling – State of the art, Progress in Oceanography, Vol. 75, 603-674. This paper is the product of the wave modelling community and it tries to make a picture of the present situation in this branch of science, exploring the previous and the most recent results and looking ahead towards the solution of the problems we presently face. Both theory and applications are considered. The many faces of the subject imply separate discussions. This is reflected into the single sections, seven of them, each dealing with a specific topic, the whole providing a broad and solid overview of the present state of the art. After an introduction framing the problem and the approach we followed, we deal in sequence with the following subjects: (Section) 2, generation by wind; 3, nonlinear interactions in deep water; 4, white-capping dissipation; 5, nonlinear interactions in shallow water; 6, dissipation at the sea bottom; 7, wave propagation; 8, numerics. The two final sections, 9 and 10, summarize the present situation from a general point of view and try to look at the future developments. a.22 Gerostathis, T., Belibassakis, K.A., Athanassoulis, G.A., 2008, A coupled-mode model for the transformation of wave spectrum over steep 3d topography. A Parallel-Architecture Implementation, Journal of Offshore Mechanics and Arctic Engineering, JOMAE, Vol.130 The problem of transformation of the directional spectrum of an incident wave system over an intermediate-depth region of strongly varying 3D bottom topography is studied in the context of linear theory. The consistent coupled-mode model, developed by Athanassoulis and Belibassakis (J. Fluid Mech. 389, pp. 275–301 (1999)) and extended to three dimensions by Belibassakis et al. (Appl. Ocean Res. 23(6), pp. 319–336 (2001)) is exploited for the calculation of the linear transfer function, connecting the incident wave with the wave conditions at each point in the field. This model is fully dispersive and takes into account reflection, refraction, and diffraction phenomena, without any simplification apart the standard intermediate-depth linearization. The present approach permits the calculation of spectra of all interesting wave quantities (e.g., surface elevation, velocity, pressure) at every point in the liquid domain. The application of the present model to realistic geographical areas requires a vast amount of calculations, calling for the exploitation of advanced computational technologies. In this work, a parallel implementation of the model is developed, using the message passing programming paradigm on a commodity computer cluster. In that way, a direct numerical solution is made feasible for an area of 25 km2 over Scripps and La Jolla submarine canyons in Southern California, where a large amount of wave measurements are available. A comparison of numerical results obtained by the present model with field measurements of free-surface frequency spectra transformation is presented, showing excellent agreement. The present approach can be extended to treat weakly nonlinear waves, and it can be further elaborated for studying wave propagation over random bottom topography. a.23 Ardhuin, F., Rascle, N., Belibassakis, K.A., 2008, Explicit wave-averaged primitive equations using a Generalized Lagrangian Mean, Journal of Ocean Modelling, Vol.20, 35-60. The generalized Langrangian mean theory provides exact equations for general wave–turbulence–mean flow interactions in three dimensions. For practical applications, these equations must be closed by specifying the wave forcing terms. Here an approximate closure is obtained under the hypotheses of small surface slope, weak horizontal gradients of the water depth and mean current, and weak curvature of the mean current profile. These assumptions yield analytical expressions for the mean momentum and pressure forcing terms that can be expressed in terms of the wave spectrum. A vertical change of coordinate is then applied to obtain glm2z-RANS equations with non-divergent mass transport in Cartesian coordinates. To lowest order, agreement is found with Eulerian mean theories, and the present approximation provides an explicit extension of known wave-averaged equations to short-scale variations of the wave field, and vertically varying currents only limited to weak or localized profile curvatures. Further, the underlying exact equations provide a natural framework for extensions to finite wave amplitudes and any realistic situation. The accuracy of the approximations is

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discussed using comparisons with exact numerical solutions for linear waves over arbitrary bottom slopes, for which the equations are still exact when properly accounting for partial standing waves. For finite amplitude waves it is found that the approximate solutions are probably accurate for ocean mixed layer modelling and shoaling waves, provided that an adequate turbulent closure is designed. However, for surf zone applications the approximations are expected to give only qualitative results due to the large influence of wave nonlinearity on the vertical profiles of wave forcing terms. a.24 Ardhuin, F., Jenkins, A., Belibassakis, K.A., 2008, Commentary on `The Three-Dimensional Current and Surface Wave Equations' by George Mellor, Journal of Physical Oceanography-JPO, Volume 38(6), pp. 1340–1350. The lowest order sigma-transformed momentum equation given by Mellor (J. Phys. Oceangr. 2003) takes into account a phase-averaged wave forcing based on Airy wave theory. This equation is shown to be generally inconsistent due to inadequate approximations of the wave motion. Indeed the evaluation of the vertical flux of momentum requires an estimation of the pressure p and coordinate transformation function s to first order in parameters that define the large scale evolution of the wave field, such as the bottom slope. Unfortunately there is no analytical expression for p and s at that order. A numerical correction method is thus proposed and verified. Alternative coordinate transforms that allow a separation of wave and mean flow momenta do not suffer from this inconsistency nor require a numerical estimation of the wave forcing. Indeed, the problematic vertical flux is part of the wave momentum flux, thus distinct from the mean flow momentum flux, and not directly relevant to the mean flow evolution. a.25 Athanassoulis, G.A., Belibassakis, K.A., Mitsoudis, D.A., Kampanis, N.A., Dougalis, V.A., 2008, Coupled-mode and finite-element solutions of underwater sound propagation problems in stratified acoustic environments, 2008, Journal of Computational Acoustics – JCA, Vol.16(1), pp.83-116. We compare the results of a coupled mode method with those of a finite element method and also of the software code COUPLE on two test problems of sound propagation and scattering in cylindrically symmetric, underwater, multilayered acoustic waveguides with range-dependent interface topographies. We observe, in general, very good agreement between the results of the three codes. In some cases in which the frequency of the harmonic point source is such that an eigenvalue of the local vertical problem remains small in magnitude and changes sign several times in the vicinity of the interface nonhomogeneity, the discrepancies between the results of the three codes increase, but remain small in absolute terms. a.26 Belibassakis, K.A., 2008, A boundary element method for the hydrodynamic analysis of floating bodies in general bathymetry regions, Engineering Analysis with Boundary Elements, 32 (2008), pp. 796-810. In this work, a hybrid technique is presented for the hydrodynamic analysis of floating bodies in variable bathymetry regions. Our method is based on the coupled-mode theory for the propagation of water waves in general bottom topography, developed by Athanassoulis and Belibassakis [Athanassoulis GA, Belibassakis KA. A consistent coupled-mode theory for the propagation of small-amplitude water waves over variable bathymetry regions. J Fluid Mech 1999;389:275–301.] and extended to 3D by Belibassakis et al. [Belibassakis KA, Athanassoulis GA, Gerostathis TP. A coupled-mode model for the refraction–diffraction of linear waves over steep three-dimensional bathymetry. Appl Ocean Res 2001;23:319–336.], which is free of any mild-slope assumption, in conjunction with a boundary integral representation of the near field in the vicinity of the floating body. Both 2D and 3D problems have been considered. In all cases the near field is represented by boundary integral representation involving simple (Rankine) sources. In the 2D case, the far-field is modelled by complete (normal-mode) series expansions derived by separation of variables in the constant-depth half-strips. In the 3D case, the far-field is modelled by an integral representation involving the appropriate Green’s function for harmonic water waves over a bottom with different depths at infinity, developed by Belibassakis and Athanassoulis [Belibassakis KA, Athanassoulis GA. Three-dimensional Green’s function for harmonic water waves over a bottom with different depths at infinity. J Fluid Mech 2004;510:267–302.]. The numerical solution is obtained by means of a low-order panel method materialising the hybrid technique. Numerical results are presented concerning floating bodies of simple geometry, lying over sloping and undulating seabeds. With the aid of systematic comparisons with benchmark solutions the convergence and accuracy of the present method in 3D has been studied, and the effects of bottom slope and curvature on the hydrodynamic characteristics (hydrodynamic coefficients and responses) of the floating bodies are illustrated and discussed.

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a.27 Prospathopoulos, A. M., Athanassoulis, G.A., Belibassakis, K.A., 2009, Three-dimensional acoustic field computations for scattering from a radially-layered cylindrical obstacle in an ocean waveguide: Low-frequency results, J. of Sound and Vibration, Vol. 319, pp.1285-1300. A solution based on coupled mode expansions is presented for the 3D problem of acoustic scattering from a radially layered penetrable cylindrical obstacle in a shallow-water plane-horizontal waveguide. Each cylindrical ring is characterized by a general, vertical sound speed and density profile (ssdp), the ocean environment around the obstacle can be also considered horizontally stratified with a depth-arbitrary ssdp, and the bottom is assumed to be rigid. The total acoustic field generated by an harmonic point source is represented as a normal-mode series expansion. The expansion coefficients are calculated exploiting the matching conditions at the cylindrical interfaces, which results in an infinite linear system. The system is appropriately truncated and numerically solved by using a recursive relation, which involves the unknown coefficients of two successive rings. Results concerning the transmission loss outside and inside obstacles consisting of three cylindrical rings are given for a typical depth-dependent ocean sound-speed profile. The presented solution can serve as a benchmark solution to the general problem of 3D acoustic scattering from axisymmetric inhomogeneities in ocean waveguides at low frequencies. a.28 Athanassoulis, G.A., Belibassakis, K.A., 2009, A novel coupled-mode theory with application to hydroelastic analysis of thick, non-uniform floating bodies over general bathymetry, Journal of Engineering for the Maritime Environment,Vol.223, pp.419-437. A new coupled-mode system of horizontal equations is presented for the hydroelastic analysis of large floating bodies or ice sheets of general, finite thickness, lying over variable bathymetry regions. The present method is based on the theory of shear deformable plates (or beams), and is derived by an enhanced representation of the elastic displacement field, containing additional elastic vertical modes and permitting shear strain and stress to vanish on both the upper and lower boundaries of the thick floating plate. This model extends third-order plate theories by Reddy and Bickford (Wang, Reddy & Lee 2000) to plates and beams of general shape. The present coupled-mode system of horizontal differential equations is obtained by means of a variational principle composed by the one-field functional of elastodynamics (see, e.g., Graff 1975, Reddy 1984) in the plate region, and the Luke's (1967) pressure functional in the water region. The wave potential in the water column is represented by means of a local mode series expansion containing an additional mode providing the appropriate correction term on the bottom boundary, when the slope is not mild. In the above sense, our method extends previous approaches concering hydroelastic problems based on thin plate theory (Porter & Porter 2004, Belibassakis & Athanassoulis 2005). In this work we focus on the scattering of linear, coupled, hydroelastic waves propagating through an inhomogeneous sea-ice environment, containing ice sheets of variable thickness and non-mildly sloped interface. Numerical results are presented in the simple 2D case, showing that the present approach efficiently models the hydroelastic problem, providing us accuracy by keeping only a few terms in the expansion. Ideas for extending our method to 3D are also discussed. a.29 Belibassakis, K.A., 2010, Roll response of ship-hull sections in variable bathymetry regions by a hybrid BEM - vortex particle method, Journal of Hydrodynamics Ser. B, Volume 22, Issue 5, Supplement 1, October 2010, Pages 413-418 (selected papers from 9th Intern. Conference on Hydrodynamics, ICHD 2010, Shanghai, China). A non-linear, hybrid method has been developed with application to the problem of roll response of ship-hull sections of general shape, floating in general bathymetry regions. Using domain decomposition, the present method is based on boundary element formulation for the representation of the non-linear potential wave motion around the floating body, in combination with vortex particle method for the generation of vorticity in the boundary layer and numerical simulation of vorticity convection and viscous diffusion in subregions close to the solid boundary. Subsequently, hydrodynamic forces on the floating body are obtained by pressure integration, and the hydrodynamic coefficients (added mass, damping) are calculated. Numerical results are presented and compared with experimental data and other methods. It is shown that the present method provides results of reasonable accuracy, illustrating that the mixing of boundary integral methods and particle methods isa useful tool for the evaluation of ship-hull characteristics in rolling motion, where viscous effects associated with boundary layer separation could be significant.

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a.30 Belibassakis, K.A., Athanassoulis, G.A., 2011, A coupled-mode system with application to nonlinear water waves propagating in finite water depth and in variable bathymetry regions, Coastal Engineering Vol. 58, pp.337-350. A non-linear coupled-mode system of horizontal equations is presented modelling the evolution of nonlinear water waves in finite depth over a general bottom topography. The vertical structure of the wave field is represented by means of a local-mode series expansion of the wave potential. This series contains the usual propagating and evanescent modes, plus two additional terms, the free-surface mode and the sloping-bottom mode, enabling to consistently treat the non-vertical end-conditions at the free-surface and the bottom boundaries. The present coupled-mode system fully accounts for the effects of non-linearity and dispersion, and the local-mode series exhibits fast convergence. Thus, a small number of modes (up to 5-6) are usually enough for precise numerical solution. In the present work, the coupled-mode system is applied to the numerical investigation of families of steady travelling wave solutions in constant depth, corresponding to a wide range of water depths, ranging from intermediate depth to shallow-water wave conditions, and its results are compared vs. Stokes and cnoidal wave theories, as well as with fully nonlinear Fourier methods. Furthermore, numerical results are presented for waves propagating over variable bathymetry regions and compared with nonlinear methods based on boundary integral formulation and experimental data, showing good agreement. a.31 Belibassakis, K.A., Gerostathis, Th., Athanassoulis, G.A., 2011, A coupled-mode model for water wave scattering by horizontal, non-homogeneous current in general bottom topography, Applied Ocean Research, Vol.33, pp. 384– 397. A coupled-mode model is developed for treating the wave-current-seabed interaction problem, with application to wave scattering by non-homogeneous, steady current over general bottom topography. The vertical distribution of the scattered wave potential is represented by a series of local vertical modes containing the propagating mode and all evanescent modes, plus additional terms accounting for the satisfaction of the free-surface and bottom boundary conditions. Using the above representation, in conjunction with unconstrained variational principle, an improved coupled system of differential equations on the horizontal plane, with respect to the modal amplitudes, is derived. In the case of small-amplitude waves, a linearised version of the above coupled-mode system is obtained, generalizing previous results by Athanassoulis & Belibassakis for the propagation of small-amplitude water waves over variable bathymetry regions. Keeping only the propagating mode in the vertical expansion of the wave potential, the present system reduces to an one-equation model, that is shown to be compatible with mild-slope model concerning wave-current interaction over slowly varying topography, and in the case of no current it exactly reduces to the modified mild-slope equation. The present coupled-mode system is discretized on the horizontal plane by using second-order finite differences and numerically solved by iterations. Results are presented for various representative test cases demonstrating the usefulness of the model, as well as the importance of the first evanescent modes and the additional sloping-bottom mode when the bottom slope is not negligible. The analytical structure of the present model facilitates its extension to fully non-linear waves, and to wave scattering by currents with more general structure. a.32 Belibassakis, 2012, Water-wave induced groundwater pressure and flow in variable bathymetry regions and sandy beaches by an enhanced coupled-mode model, Ocean Engineering Vol. 47, pp. 104–118. An enhanced coupled-mode system is developed for modeling wave-induced pressure and groundwater flow in variable bathymetry coastal regions, in the layer under the permeable seabed. The sea bottom is assumed of general shape, characterized by sloping parts and undulations, without restrictions concerning mildness of bottom slope and curvature. The present model is based on a simplified version of the storage and momentum equations, corresponding to large values of stiffness ratio of the porous medium, permitting prediction of wave-induced groundwater pressure and flow in the case when the elastic motion of the seabed is very small and could be approximately neglected. The representation of the wave pressure field is based on a local-mode series expansion in the water column and the porous medium, consisted of propagating and evanescent modes, and defined by formulating and solving vertical eigenvalue problems at each local horizontal position. The latter series is enhanced by appropriate terms (the sloping-interface mode) enabling consistent satisfaction of the interface conditions at the seabed and providing fast convergence. Numerical results are presented and compared against predictions by other methods and measured data, illustrating the applicability of the present model to variable bathymetry coastal regions and sandy beaches.

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a.33 Belibassakis K.A., Gerostathis, Th.P, Kostas K.V., Politis C.G., Kaklis P.D., Ginnis A.I., Feurer C., 2013, A BEM-isogeometric method for the ship wave-resistance problem, Ocean Engineering Vol. 60, pp. 53–67. In the present work IsoGeometric Analysis is applied to the solution of the Boundary Integral Equation associated with the Neumann-Kelvin problem and the calculation of the wave resistance of ships. As opposed to low-order panel methods, where the body is represented by a large number of quadrilateral panels and the velocity potential is assumed to be piecewise constant (or approximated by low degree polynomials) on each panel, the isogeometric concept is based on exploiting the same NURBS basis, used for representing exactly the body geometry, for approximating the singularity distribution (and, in general, the dependent physical quantities). In order to examine the accuracy of the present method, numerical results obtained in the case of submerged and surface piercing bodies are compared against analytical solutions, experimental data and predictions provided by the low-order panel or other similar methods appeared in the pertinent literature, illustrating the superior efficiency of the isogeometric approach. The present approach by applying Isogeometric Analysis and Boundary Element Method to the linear NK problem has the novelty of combining modern CAD systems for ship-hull design with computational hydrodynamics tools. a.34 Belibassakis K.A., Politis G.K., 2013, Hydrodynamic performance of flapping wings for augmenting ship propulsion in waves, Ocean Engineering Vol.72, pp.227-240. The present work deals with the hydrodynamic analysis of flapping wings located beneath the hull of the ship and operating in random waves, while travelling at constant forward speed. The system is investigated as an unsteady thrust production mechanism, augmenting the overall ship propulsion. The main arrangement consists of a horizontal wing in vertical motion induced by ship heave and pitch, while pitching about its own pivot axis that is actively set. A vertical oscillating wing-keel is also considered in transverse oscillatory motion, which is induced by ship rolling and swaying. Ship flow hydrodynamics are modeled in the framework of linear theory and ship responses are calculated taking into account the additional forces and moments due to the above unsteady propulsion systems. Subsequently, a non-linear 3D panel method including free wake analysis is applied to obtain the detailed characteristics of the unsteady flow around the flapping wing. Results presented illustrate significant thrust production, reduction of ship responses and generation of anti-rolling moment for ship stabilization, over a range of motion parameters. Present method can serve as a useful tool for assessment, preliminary design and control of the examined thrust-augmenting devices, enhancing the overall performance of a ship in waves. a.35 Belibassakis, Κ.Α., Tsoukala VK., Katsardi V., 2014, Three dimensional wave diffraction in the vicinity of openings in coastal structures, Applied Ocean Research, Vol.45, 40-54 Wave transformation through openings in coastal structures is dominated by 3D diffraction effects due to sudden changes of water depth, along with the finite width of the channel. In the present work, a novel coupled-mode model, based on eigenfunctions expansions of the Laplace equation, is developed and applied to the numerical solution and the detailed representation of the local 3D wave flow problem in the vicinity of the opening. The harmonic wave field is excited by plane incident wave propagating normally or at an angle with respect to the axis of the opening / channel. The numerical solution converges rapidly, permitting the series truncation at its first terms. The proposed method fully accounts for the 3D diffraction effects and produces necessary information to further couple with mild-slope models describing wave propagation and transformation in coastal regions in the presence of breakwaters and coastal structures containing openings. Calculated results are presented for waves propagating in regions with breakwaters with openings simulating flushing culverts and compared against experimental measurements obtained in a 3D wave basin. a.36 Filippas, E., Belibassakis K.A., 2014, Hydrodynamic analysis of flapping-foil thrusters operating beneath the free surface and in waves, Engineering Analysis with Boundary Elements, Vol.41, 47-59. Oscillating wings are investigated as unsteady thrusters, augmenting ship's overall propulsion in waves. Flapping propulsor's heave is induced by ship's motions, while pitching motion is set by an active

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control mechanism. For the detailed investigation of the free-surface effects, a two-dimensional panel method is developed for the hydrodynamic analysis of the flapping hydrofoil. The instantaneous angle of attack is influenced by foil's oscillatory motion and the incident waves. We consider moderate submergence and speed, permitting us to approximately neglect effects of breaking waves and cavitation, and linearize the free-surface boundary conditions and the trailing vortex wake dynamics. Numerical calculations are presented concerning the performance of the developed BEM over a range of motion parameters and compared against other methods and experimental data. Our analysis indicates that significant efficiency is achieved under optimal operating conditions and the free surface effects cannot be neglected. In the presence of waves the thrust coefficient is observed to raise well above its value in infinite domain, with maximum gain reaching 20%, for appropriate selection of the parameters. The present method could serve as a useful tool for the assessment, preliminary design and control of the studied system, extracting energy from sea waves for marine propulsion. a.37 Diakaki Chr., Panagiotidou N., Pouliezos A., Kontes G, Stavrakakis G., Belibassakis K., Gerostathis Th., Livanos G., Pagonis D.-N., Theotokatos G., 2014, A decision support system for the development of voyage and maintenance plans for ships, Inter. Journal of Decision Support Systems (InterScience Publishers, in press). The waterborne sector faces nowadays significant challenges due to several environmental, financial and other concerns. Such challenges may be addressed, among others, by optimising voyage plans, and diagnosing as early as possible engine failures that may lead to performance degradation. These two issues are addressed by the decision support system (DSS) presented herein, which focuses on the operation of merchant ships. For the development of voyage plans, a multicriteria decision problem is developed and handled with the PROMETHE method, while a multivariable control chart is used for the fault diagnosis problem. A MATLAB-based software implementation of the DSS has been developed adopting a modular architecture, while, in order to provide a generic software solution, the required input data are retrieved from dedicated web-services, following specific communication and data exchange protocols. a.38 Belibassakis K.A., Athanassoulis G.A., Papathanassiou T.K., Filopoulos, S.P., Markolefas S., 2014, Acoustic wave propagation in inhomogeneous, layered waveguides based on modal expansions and hp-FEM, Wave Motion, Vol. 51, 1021-1043. A new model is presented for harmonic wave propagation and scattering problems in non-uniform, stratified waveguides, governed by the Helmholtz equation. The method is based on a modal expansion, obtained by utilizing cross-section basis defined through the solution of vertical eigenvalue problems along the waveguide. The latter local basis is enhanced by including additional modes accounting for the effects of inhomogeneous boundaries and/or interfaces. The additional modes provide implicit summation of the slowly convergent part of the local-mode series, rendering the remaining part to be fast convergent, increasing the efficiency of the method, especially in long-range propagation applications. Using the enhanced representation, in conjunction with an energy-type variational principle, a coupled-mode system of equations is derived for the determination of the unknown modal-amplitude functions. In the case of multilayered environments, h- and p-FEM have been applied for the solution of both the local vertical eigenvalue problems and the resulting coupled mode system, exhibiting robustness and good rates of convergence. Numerical examples are presented in simple acoustic propagation problems, illustrating the role and significance of the additional mode(s) and the efficiency of the present model, that can be naturally extended to treat propagation and scattering problems in more complex 3D waveguides. a.39 Papathanasiou T.K., Belibassakis K.A., 2014, Hydroelastic analysis of VLFS based on a consistent coupled mode system and FEM, The IES Journal Part A: Civil & Structural Engineering, Taylor & Francis, Vol. 7, No. 3, 195-206. Three models for the interaction of water waves with large floating elastic structures are analysed. The first model, based on the Euler Bernoulli beam theory, has already been extensively studied. The second is based on the Rayleigh beam equation. The third approach utilises the Timoshenko approximation and is thus capable of incorporating shear deformation and rotary inertia effects. A novelty of the proposed hydroelastic systems is the consistent local mode expansion of the underlying hydrodynamic field interacting with the floating structure, which leads to coupled-mode systems with respect to the modal amplitudes of the wave potential and the surface elevation. This representation is rapidly convergent to the solution of the full hydroelastic problem. The dispersion relations of these

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models are derived and analysed, supporting at a next stage the efficient development of finite element method solvers of the coupled system. a.40 Belibassakis, K.A., Athanassoulis, G.A., Gerostathis, Th., 2014, Directional wave spectrum transformation in the presence of strong depth and current inhomogeneities by means of coupled-mode model, Ocean Engineering, Vol. 87, 84–96. A variety of engineering applications, including interaction of waves with coastal fixed or floating structures, coastal morphodynamics and harbour maintenance, requires detailed information about nearshore and onshore wave conditions. Since information concerning sea states is usually available offshore, there is need for developing appropriate models transforming the offshore wave conditions to nearshore ones. In the present work, a fully dispersive coupled-mode model is exploited to implement an offshore to nearshore wave spectrum transformation, in the presence of depth and current inhomogeneities. This model is based on appropriate local-mode series expansions, containing the propagating and evanescent modes, plus an additional term enabling the satisfaction of the boundary condition on the sloping parts of the bottom. The wave spectrum transformation is achieved by defining and calculating a distributed transfer function, connecting incident wave components with wave conditions at each point in the domain. The model takes full account of reflection, refraction, and diffraction phenomena, due to strongly varying, 3D bottom topography and ambient currents, as well as dissipation of wave energy due to bottom friction and wave breaking. Numerical results are compared with results obtained by other methods and experimental data, demonstrating the usefulness and practical applicability of the present approach. a.41 Ginnis A.I., Kostas K.V., Politis C.G., Kaklis P.D., Belibassakis K.A., Gerostathis, Th.P, Scott M.A., Hughes T.J.R., 2014, Isogeometric boundary-element analysis for the wave-resistance problem using T-splines, Computer Methods in Applied Mechanics and Engineering, Vol.279, 425-439. In this paper we couple collocated Boundary Element Methods (BEM) with unstructured analysis-suitable T-spline surfaces for solving a linear Boundary Integral Equation (BIE) arising in the context of a ship-hydrodynamic problem, namely the so-called Neumann–Kelvin problem, following the formulation by Brard (1972) and Baar and Price (1988). The local-refinement capabilities of the adopted T-spline bases, which are used for representing both the geometry of the hull and approximating the solution of the associated BIE, in accordance with the Isogeometric concept proposed by Hughes et al. (2005), lead to a solver that achieves the same error level for many fewer degrees of freedom as compared with the corresponding NURBS-based Isogeometric-BEM solver recently developed in Belibassakis et al. (2013). In this connection, this paper makes a step towards integrating modern CAD representations for ship-hulls with hydrodynamic solvers of improved accuracy and efficiency, which is a prerequisite for building efficient ship-hull optimizers. a.42 Tsoukala VK., Katsardi V., Belibassakis, Κ.Α., 2014, Wave transformation through flushing culverts operating at seawater level in coastal structures Ocean Engineering Vol.89, 211–229. The placement of flushing culverts in breakwaters is a simple way to counteract a decline in water quality in harbour basins. A series of 63 experiments, which were conducted in a physical model of a breakwater in a 2D wave flume, are used to investigate the effect of the wave properties as well as the geometrical characteristics of the flushing culvert placed on breakwaters, in the temporal water surface profiles, the harmonic generation and the transmission coefficient. It is shown (i) that the harmonic generation downwave of the structure is more intense when wave nonlinearity increases; (ii) the harmonic generation and the transmission coefficient is mostly affected by the culvert's dimensions, especially the culvert's width as it is associated with the energy transmitted to the lee side of the structure and with diffraction. A 2D coupled-mode system (CMS) model is applied for the numerical simulation of waves propagating through flushing culverts at sea water level that are never perfectly filled with water. Good comparisons with the experimental results for linear and weakly non-linear waves and wider culverts are shown; proving the usefulness of the CMS model in calculating the effectiveness of a flushing culvert in an every-day basis of harbour function. a.43 Papathanasiou T. K., Karperaki A., Theotokoglou E.E., Belibassakis K.A., 2015, A higher order FEM for time-domain hydroelastic analysis of large floating bodies in inhomogeneous shallow water environment, Proc. Royal Society of London A: Mathematical, Physical and Engineering Sciences . A Vol. 471: 20140643.

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The study of wave action on large, elastic floating bodies has received considerable attention, finding applications in both geophysics and marine engineering problems. In this context, a higher order finite-element method (FEM) for the numerical simulation of the transient response of thin, floating bodies in shallow water wave conditions is presented. The hydroelastic initial-boundary value problem, in an inhomogeneous environment, characterized by bathymetry and plate thickness variation, is analysed for two configurations: (i) a freely floating strip modelling an ice floe or a very large floating structure and (ii) a semi-fixed floating beam representing an ice shelf or shore fast ice, both under long-wave forcing. The variational formulation of these problems is derived, along with the energy conservation principle and the weak solution stability estimates. A special higher order FEM is developed and applied to the calculation of the numerical solution. Results are presented and compared against established methodologies, thus validating the present method and illustrating its numerical efficiency. Furthermore, theoretical results concerning the energy conservation principle are verified, providing a valuable insight into the physical phenomenon investigated. a.44 Belibassakis K.A., Filippas, E., 2015, Ship propulsion in waves by actively controlled flapping foils, Applied Ocean Research Vol. 52, 1–11 Flapping wings located beneath or to the side of the hull of the ship are investigated as unsteady thrusters, augmenting ship propulsion in waves. The main arrangement consists of horizontal wing(s) in vertical oscillatory motion which is induced by ship heave and pitch, while rotation about the wing pivot axis is actively controlled. In this work we investigate the energy extraction by the system operating in irregular wave conditions and its performance concerning direct conversion to propulsive thrust. More specifically, we consider operation of the flapping foil in waves characterized by a spectrum, corresponding to specific sea state, taking into account the coupling between the hull and the flapping foil dynamics. The effect of the wavy free surface is accounted for through the satisfaction of the corresponding boundary conditions and the consideration of the wave velocity on the formation of the incident flow. Numerical results concerning thrust and power coefficients are presented, indicating that significant thrust can be produced under general operating conditions. The present work can be exploited for the design and optimum control of such systems extracting energy from sea waves for augmenting marine propulsion in rough seas, with simultaneous reduction of ship responses offering also dynamic stabilization. a.45 Papathanasiou T.K., Karperaki A., Theotokoglou E.E., Belibassakis K.A., 2015, Hydroelastic analysis of ice shelves under long wave excitation, Nat. Hazards Earth Syst. Sci., Vol.15, 1851–1857. The transient hydroelastic response of an ice shelf under long wave excitation is analysed by means of the finite element method. The simple model, presented in this work, is used for the simulation of the generated kinematic and stress fields in an ice shelf, when the latter interacts with a tsunami wave. The ice shelf, being of large length compared to its thickness, is modelled as an elastic Euler-Bernoulli beam, constrained at the grounding line. The hydrodynamic field is represented by the linearised shallow water equations. The numerical solution is based on the development of a special hydroelastic finite element for the system of governing of equations. Motivated by the 2011 Sulzberger Ice Shelf (SIS) calving event and its correlation with the Honshu Tsunami, the SIS stable configuration is studied. The extreme values of the bending moment distribution in both space and time are examined. Finally, the location of these extrema is investigated for different values of ice shelf thickness and tsunami wave length. a.46 Tsoukala, V., Chondros, M.,…, Belibassakis, K.A., Makropoulos, Ch., 2016, An integrated wave modelling framework for extreme and rare events for climate change in coastal areas – the case of Rethymno-Crete, Oceanologia Vol. 58, 71-89. Coastal floods are regarded as among the most dangerous and harmful of all natural disasters affecting urban areas adjacent to the shorelines. Rapid urbanization combined with climate change and poor governance often results in significant increase of flood risk, especially for coastal communities. Wave overtopping and wave run-up are the key mechanisms for monitoring the results of coastal flooding and as such, significant efforts are currently focusing on their predicting. In this paper, an integrated methodology is proposed, accounting for wave overtopping and wave run-up under extreme wave scenarios caused by storm surges. By taking advantage of past and future climatic projections of wind data, a downscaling approach is proposed, a.47 Gerostathis Th., Belibassakis K.A., Athanassoulis G.A., 2016, 3D hydroelastic analysis of very large

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floating bodies over variable bathymetry regions, Journal of Ocean Engineering and Marine Energy Vol.2, 159-175. The coupled-mode model developed by Belibassakis & Athanassoulis (2005) is extended and applied to the hydroelastic analysis of three-dimensional large floating bodies of shallow draft lying over variable bathymetry regions. The method is also applicable to the problem of wave interaction with ice sheets of small thickness. A general bathymetry is assumed, characterised by a continuous depth function, joining two regions of constant, but possibly different, depth. We consider the scattering problem of harmonic incident surface waves, under the combined effects of variable bathymetry and a floating elastic plate of orthogonal planform shape. Under the assumption of small-amplitude waves and plate deflections, the hydroelastic problem is formulated within the context of linearised water-wave and thin elastic-plate theory. In order to consistently treat the wave field beneath the elastic floating plate, down to the sloping bottom boundary, a complete, local, hydroelastic-mode series expansion of the wave field is used, enhanced by an appropriate sloping-bottom mode. The latter enables the consistent satisfaction of the Neumann bottom-boundary condition on a general topography. Numerical results concerning floating structures over flat and inhomogeneous seabeds are presented, and the effects of wave direction, bottom slope and bottom corrugations on the hydroelastic responses are discussed. a.48 Karperaki A., Belibassakis K.A., Papathanasiou T. K., 2016, Time-domain, shallow-water hydroelastic analysis of VLFS elastically connected to the seabed, Marine Structures Vol. 48, 33-51. In order to ensure the safe operation of a VLFS, a combination of mooring, breakwater and other motion reducing systems is employed. In the present work, the transient hydroelastic response of a floating, thin elastic plate, elastically connected to the seabed, is examined. The plate is modelled as an Euler-Bernoulli strip, while the linearized shallow water equations are used for the hydrodynamic modelling. Elastic connectors are approximated by a series of simple spring-dashpot systems positioned along the strip. A higher order finite element scheme is employed for the calculation of the hydroelastic response of the strip-connector configuration over the shallow bathymetry. After the definition of the initial-boundary value problem, its variational form is derived and discussed. Next, on the basis of the aforementioned formulation, an energy balance expression is obtained. The effect of variable bathymetry on the response of a two connector-strip system is examined by means of three seabed profiles featuring a flat bottom, an upslope and a downslope environment. For the flat bottom case, the strip response mitigating effect exerted by the employment of two and three elastic connectors is considered. Finally, by means of the derived energy balance equation, the energy exchange is monitored, providing a valuable insight into the transient phenomena that take place in the studied configurations. a.49 Touboul J., Charland J., Rey V., Belibassakis K., 2016, Extended Mild-Slope equation for surface waves interacting with a vertically sheared current Coastal Engineering Vol. 116, 77–88. Propagation of water waves in coastal zones is mainly affected by the influence of currents and bathymetry variations. Models describing wave propagation in coastal zones are often based on the numerical solution of the Mild Slope equation (Kirby, 1984). In this work, an extension of this equation is derived, taking into account the linear variation of the current with depth, which results in a constant horizontal vorticity, slowly varying horizontally, within the background current field. The present approach is based on the asymptotic expansion of the depth-integrated lagrangian assuming the linear variation of the background current with depth. With the aid of selected examples the role of this horizontal vorticity, associated with the assumed background current velocity profile, is then illustrated and emphasized, demonstrating its effect on the propagation of water waves in coastal areas. a.50 Makris Ch., Galiatsatou P., …., Belibassakis Κ., Rusu E., 2016, Climate change effects on the marine characteristics of the Aegean and Ionian Seas, Ocean Dynamics, DOI10.1007/s10236-016-1008-1. This paper addresses the effects of estimated climate change on the sea-surface dynamics of the Aegean and Ionian Seas (AIS). The main aim is the identification of climate change impacts on the severity and frequency of extreme storm surges and waves in areas of the AIS prone to flooding. An attempt is made to define design levels for future research on coastal protection in Greece. Extreme value analysis is implemented through a nonstationary Generalized Extreme Value distribution function, incorporating time harmonics in its parameters, by means of statistically defined criteria. A 50-year timespan analysis is adopted and changes of means and extremes are determined. A Regional

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Climate Model (RegCM3) is implemented with dynamical downscaling, forced by ECHAM5 fields under 20C3M historical data for the 20th century and the SRES-A1B scenario for the 21st century. Storm surge and wave models (GreCSSM and SWAN, respectively) are used for marine climate simulations. Comparisons of model results with reanalysis and field data of atmospheric and hydrodynamic characteristics, respectively, are in good agreement. Our findings indicate that the dynamically downscaled RegCM3 simulation adequately reproduces the present general circulation patterns over the Mediterranean and Greece. Future changes in sea level pressure and mean wind fields are estimated to be small, yet significant for marine extremes. In general, we estimate a projected intensification of severe wave and storm surge events during the 1st half of the 21st century and a subsequent storminess attenuation leading to the resettlement of milder extreme marine events with increased prediction uncertainty in the 2nd half of the 21st century. B. CONFERENCE PAPERS (reviewed on the basis of full text) b.1 Politis, G.K., Belibasakis, K.A., Nakos, D., 1987, Panel Methods vs Vortex Lattice Methods in Marine Propeller Design, 4th International Congress of the International Maritime Association of East Mediterranean, IMAEM’87, Varna, Bulgaria. The design problem for a marine propeller has been formulated and solved using second-order eight-node quadrilateral panels. An extensive sensitivity analysis is presented showing that sufficiently exact solutions of the design problem can be obtained with a small number of panels. Comparison of the panel method with the vortex lattice method for a sample of design cases shows systematic differences in the calculated pitch distributions and propeller thrust and torque characteristics with trends confirmed by practical design experience. Since computer space and time requirements for the two methods are comparable, the panel method approach seems to be a preferable alternative for marine propeller design. b.2 Belibasakis, K.A., Politis, G.K., 1989, Calculation of Three Dimensional Potential Flows using Surface Vorticity Distributions, 5th Int. Conference on Computational Methods and Experimental Measurements, CMEM'89, Capri, Italy. A numerical method is presented for the calculation of incompressible, non-lifting flow velocity and pressure distributions, around arbitrary three-dimensional bodies. The method is based on a vorticity boundary integral equation formulation of an inner problem, equivalent to the external Neumann problem, using the assumption of zero tangential velocity for the inner boundary. The geometry of the body is approximated by using second-order boundary elements, while the unknown surface vorticity distribution is approximated using zero order boundary elements, in order for the surface vorticity condition to be satisfied identically. Application of the developed numerical scheme has shown that very accurate results can be obtained using sparse computational grids, enabling thus the calculation of complex flow fields with less computer time and memory requirements than other known methods. b.3 Belibasakis, K.A., Politis, G.K., 1989, Calculation of Three Dimensional Lifting Flows using Surface Vorticity Distributions, 4th Int. Symp. on Practical Design of Ships, PRADS'89, Varna, Bulgaria. A numerical method is presented for the calculation of incompressible, lifting flow velocity and pressure distributions, around arbitrary three-dimensional bodies. The method is based on a vorticity boundary integral equation formulation of an inner problem, equivalent to the external Neumann problem, and satisfaction of a nonlinear Kutta condition at the trailing edge. Application of the developed numerical scheme has shown that very accurate results can be obtained using sparse computational grids, enabling thus the calculation of complex flow fields with less computer time and memory requirements than other known methods. b.4 Politis, G.K., Belibasakis, K.A., 1990, Application of Panel Methods to Linearized Lifting Surface Propeller Performance Problem, 5th Intern Congress on Marine Technology, IMAEM'90, Athens, Greece.

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The steady lifting surface propeller performance problem is formulated using generalised tensor analysis, as a system of an integral and a differential equation in parametric space. A numerical solution is presented using surface boundary elements to discretize the unknown surface vorticity distributions. Comparison of the results of the proposed method with experimental data as well as with other theories show that accurate predictions of the blade pressure distribution and the integrated propeller open water characteristics can be obtained with relatively low cost. Consequently, the proposed method can be used as a time and cost effective alternative of the propeller model open water experiments in the process of analysing the ship powering performance. b.5 Athanassoulis, G.A., Belibassakis, K.A, 1997, The integrated software Amfitrite with application to hydroacoustic calculations in the Greek Sea environment, 5th Hellenic Symposium of Oceanography, Kavala, Greece, April 1997 (in Greek). The ‘Amfitrite’ integrated software is developed in the framework of ‘Amfitrite’ project, which is funded by the Hellenic Navy General Staff, and is carried out at the Laboratory of Ship and Marine Hydrodynamics of the National Technical University of Athens. The purpose of the ‘Amfitrite’ project is the systematic study of the hydroacoustic characteristics of the Greek Seas. In particular, one of the principal goals of the project is the development of an integrated, user-friendly software, enabling by means of a graphical user interface system the retrieval, management and updating of environmental (geographical, oceanographic, hydroacoustic and geoacoustic) data, the execution of computations by means of available and well-established computer codes, and the visualisation of the results concerning acoustic propagation losses in underwater sound transmissions. In the present work a brief description of the integrated ‘Amfitrite’ software is given, and selected examples from its application to typical environments from the Aegean Sea are presented. b.6 Belibassakis, K.A., Politis, G.K., Triantafyllou, M.S., 1997, Application of the Vortex Lattice Method to the propulsive performance of a pair of oscillating wing-tails, Proc. 8th Inter. Conf on Computational Methods and Experimental Measurements, CMEM’97, Rhodes, Greece. A 3-D unsteady vortex lattice technique is applied to the analysis of a pair of vertical oscillating wing tails, in order to investigate quantitatively its propulsive performance. Each lifting component undergoes a combined transverse and angular motion at the same frequency, in a uniform inflow condition. A free wake analysis is incorporated in order to account for the effects of non-linearity, especially at increased amplitudes of oscillatory motion. Wing thickness effects are taken into account by an appropriate linearisation of the no-entrance boundary condition, and the effects of viscosity by means of a frictional drag coefficient applied to the solid surface. Numerical results are presented vs. experimental measurements for the propulsion thrust coefficient and the efficiency of the system over a range of motion parameters, including wing's aspect ratio, Strouhal number, feathering parameter and phase lag between oscillatory motions. These results indicate the significance of 3-D effects and show that the present technique, after appropriate elaboration, especially as concerns unsteady LE flow separation and stall effects, can serve for the design of this kind of propulsive systems with optimised performance.

b.7 Athanassoulis, G.A., Belibassakis, K.A., 1997, Water wave Green function for a 3D uneven-bottom

problem with different depths at infinity, Proc. IUTAM Symposium on Computational Methods in

Unbounded Domains, Intern. Union of Theoretical and Applied Mechanics, University of Colorado,

U.S.A., July 1997, Kluwer.

The water wave field generated by a pulsating point source which is located in a region with variable

bottom bathymetry has been studied. The main features of the problem are: (i) The far-field water

depths for x → +∞ and x → −∞ are different. (ii) No asymptotic simplification based on deep or

shallow water assumptions are made. The main results of this work are: (a) The problem is

reformulated as a boundary value problem for a system of second-order ODEs in a bounded interval

( )a x b≤ ≤ . (b) The far-field wave pattern of the initial problem presents a strong azimuthal

anisotropy, its main features being a shadow zone centered in area of variable bathymetry. As

x → ±∞ , in sectors not including the variable bathymetry region, the asymptotic behaviour of the far

field approaches the standard one, corresponding to the constant depth h1 or h3 , respectively.

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b.8 Politis, K.A., Belibassakis, K.A., 1999, High propulsive efficiency by a system of oscillating wing tails, 9th Inter. Conf. on Computational Methods and Experimental Measurements, CMEM’99, Sorrento, Italy, 1999. The analysis of harmonically oscillating wing tails, considered as an unsteady propulsion system, is extended to the case of large amplitudes of oscillatory motion. Each wing undergoes a combined transverse and angular motion, at the same frequency, and in a uniform inflow. A 3-D unsteady vortex-lattice technique is applied to model the flow around the system, including leading-edge separation and dynamic-stall effects. A free-wake analysis is incorporated in order to account for the effects of non-linear wake dynamics, at high translation velocities and at increased amplitudes of oscillatory motion. Numerical results are presented vs. experimental measurements for the thrust coefficient and the efficiency of the system over a range of motion parameters, including reduced frequency, Strouhal number, feathering parameter and phase lag between oscillatory motions. These results indicate that high efficiency can be obtained under conditions of optimal wake formation. Thus, the present method can serve as a useful tool for assessment and the preliminary design of this kind of nonconventional propulsive systems with optimised performance. b.9 Athanassoulis, G.A., Belibassakis, K.A., 1999, A coupled-mode propagation/dissipation model of small-amplitude water waves over variable bathymetry regions, Coastal Engineering 99, Lemnos, Greece 1999. An enhanced coupled-mode system of equations has been developed for the solution of the water-wave propagation problem over a bed, characterised by variable depth with locally steep bottom slope and large curvature. Except of the propagating and the evanescent modes, an additional mode with non-zero vertical derivative is included, permitting the exact satisfaction of the sloping-bottom boundary condition, for any value of the bottom slope. The effect of wave energy dissipation due to bottom friction is taken into account by including an appropriate imaginary part in the wavenumber. Numerical results demonstrating the practical applicability of the present method are given. b.10 Athanassoulis, G.A., Belibassakis, K.A., Gerostathis, Th., 2000, A coupled-mode theory for the diffraction of water waves by localized scatterers over a parallel-contour bathymetry, WAVES 2000 Mathematical and Numerical Aspects of Wave Propagation, organized by SIAM and INRIA, Spain, June 2000. The consistent coupled-mode theory derived by Athanassoulis & Belibassakis (1999) is generalized in (2+1) dimensions and applied to the diffraction problem of small-amplitude water waves from localized 3D scatterers superimposed over a parallel-contour bathymetry. The total wave field is decomposed into an incident field carrying out the effects of the parallel-contour bathymetry, and an associated diffraction field with forcing restricted only on the surface of the localized scatterer(s). The wave parameters in the horizontal space are different at infinity in different directions, rendering the estimation of the diffraction far-field pattern a part of the problem. The vertical distribution of the diffraction potential is represented by a uniformly convergent series of local vertical modes. This series consists of the vertical eigenfunctions associated with the propagating and all evanescent modes, plus an additional mode, accounting for the bottom boundary condition when the bottom slope is not negligible. By applying an appropriate variational principle, the diffraction problem is reduced to a system of horizontal differential equations in the propagation space (the diffraction system). No simplifying assumptions concerning the bottom slope and curvature are made, and thus, the diffraction system is equivalent to the 3D boundary-value problem for the diffraction potential. To restrict the support of the diffraction system, an absorbing layer (the Berenger PML model) is introduced and optimized by direct minimization of the reflection coefficient. b.11 Belibassakis K.A., Politis G.K., 2002, Unsteady performance of propellers with non-conventional blade geometry by a vorticity based panel method, 10th Congress of International Maritime Association of the Mediterranean, ΙΜΑΜ 2002, Rethymnon-Crete. A boundary integral equation technique, involving surface vorticity distributions as the boundary unknowns, is applied to solve the unsteady marine propeller performance problem, resulting from the operation of a propeller in inclined flow or in the ship's wake, under the assumption of weak interaction between the sheared onset flow and the propeller induced velocity. The mathematical

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formulation is based on a system of second-kind, Fredholm-type boundary integral equations, obtained by the velocity representation theorem. This system is characterised by weakly singular kernels, which permits an efficient and accurate inversion. A pressure-type Kutta condition is satisfied along the trailing edge of the blades. Extensive comparisons are presented between the present method, other boundary element techniques and experimental measurements, showing that reliable information concerning the time-history of the blade pressure distribution and the integrated propeller characteristics can be obtained, supporting, thus, the detailed design procedure of marine propellers. Our numerical results are focused on the unsteady performance of propellers with non-conventional blade geometry (increased skew, pitch and expanded area ratio, with large chord-length distribution), operating in inclined flow conditions, and in circumferentially varying incoming flow, representing the ship's wake. Although the present work is restricted to potential flow applications, the surface vorticity formulation can be used to couple rotational flow and potential flow in a direct way. This approach, in conjunction with solvers of the vorticity transport equation, or the Euler equations, in three dimensions, permits us to improve the numerical predictions concerning the unsteady propeller analysis and the propeller-hull interaction problems, overcoming the limitations of weak interaction assumption. b.12 Athanassoulis, G.A., Belibassakis, K.A., Gerostathis, Th., 2002, A coupled-mode model for acoustic scattering by a general seafloor topography, 10th Congress of International Maritime Association of the Mediterranean, ΙΜΑΜ 2002, Rethymnon-Crete. A consistent coupled-mode theory, derived by Athanassoulis et al (1998), is applied to the three-dimensional scattering of acoustic waves by general seafloor topography. The total acoustic field is decomposed into an (propagating) field carrying out the effects of the background (parallel-contour) bathymetry, and an associated scattering field with forcing restricted only on the surface of three dimensional inhomogeneities (localized scatterers). The wave parameters in the horizontal (propagation) space are different at infinity in different directions, rendering the estimation of the scattering far-field pattern a part of the problem. The vertical distribution of the scattering potential is represented by a uniformly convergent series of local modes. This series consists of the vertical eigenfunctions associated with the propagating and evanescent modes, plus an additional mode, accounting for the sloping bottom boundary condition, which is important when the bottom slope is not negligible. By applying a variational principle, the scattering problem is reduced to a system of horizontal differential equations in the propagation space (the scattering system). No simplifying assumptions concerning the bottom slope and curvature are made, and thus, the scattering system is equivalent to the complete 3D boundary-value problem for the scattering potential. To restrict the support of the scattering system, the Perfectly Matched Layer (PML) absorbing model, introduced by Berenger (1994) for the absorption of electromagnetic waves, and formulated for the Helmholtz equation by Turkel & Yefet (1998) and by Collino & Monk (1998), is optimized, by direct minimization of the reflection coefficient. Then, the PML model is applied as the closure condition of the scattering system, at a finite distance far from the localized three-dimensional bathymetric features. Results are presented concerning the optimum choice of the discrete PML coefficients for various values of the physical and numerical parameters, which are useful for the discretization of the scattering system by a second-order finite difference scheme. The present coupled-mode model can provide an improved rate of convergence of the modal series ensuring the uniform convergence of the three-dimensional acoustic field up to and including the boundaries, and produces solutions consistent with the conservation of energy. b.13 Belibassakis, K.A., Athanassoulis, G.A., 2002, Harmonic generation past a generally shaped bottom profile, 10th Congress of International Maritime Association of the Mediterranean, ΙΜΑΜ 2002, Rethymnon-Crete. The second-order Stokes water-wave theory has been extended by Belibassakis & Athanassoulis (2001), to the case of a generally-shaped bottom profile connecting two half-strips of constant (but possibly different) depths, initiating a method for generalizing the Stokes hierarchy of second and higher order theory without the assumption of spatial periodicity. Apart from the Stokes small-amplitude expansibility assumption, no additional asymptotic assumptions have been introduced, e.g., bottom slope and curvature may be arbitrary, provided that the resulting wave dynamics is Stokes compatible. Accordingly, this theory permits the study of various wave phenomena, both linear (propagation, reflection, diffraction) and nonlinear (harmonic generation, non-resonant interaction), arising from the interaction of weakly non-linear waves with a general bottom topography, in intermediate water depth. In the present work, we focus on the phenomenon of second-order harmonic generation. The theoretical predictions have been validated against experimental results and fully nonlinear numerical

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solutions. It has been found that the present theory correctly predicts the second-order harmonic generation, and the amplitude non-linearity of the second harmonic, over an abrupt shoal, up to a limiting configuration, after which a large amount of energy is transferred to higher harmonics. Non-resonant interaction between first and second free harmonics in the transmission region is also correctly predicted. b.14 Athanassoulis, G.A., Belibassakis, K.A., 2002, A Coupled-Mode, Fully-dispersive, Weakly-nonlinear Model for Water Waves over a General Bathymetry, 12th Intern. Offshore and Polar Conference and Exhibition, ISOPE2002, Kitakyushu, Japan In this paper a coupled-mode system of horizontal equations is derived with the aid of Luke’s (1967) variational principle, which models the evolution of nonlinear water waves in intermediate depth over a general bathymetry. The vertical structure of the wave field is exactly represented by means of a local-mode series expansion of the wave potential, Athanassoulis & Belibassakis (2000). This series contains the usual propagating and evanescent modes, plus two additional modes, enabling to consistently treat the non-vertical end-conditions at the free-surface and the bottom boundaries. The system fully accounts for the effects of non-linearity and dispersion. In the present work the fully nonlinear coupled-mode system is simplified keeping only up to second-order terms, and the derived weakly non-linear model is applied to water waves propagating over a flat bottom and over an arbitrary bathymetry, in the time and in the frequency domain b.15 Athanassoulis, G.A., Belibassakis, K.A., 2002, A nonlinear coupled-mode model for water waves over a general bathymetry, 21st International Conference on Offshore Mechanics and Arctic Enginnering, OMAE2002 Oslo, Norway A non-linear coupled-mode system of horizontal equations is derived with the aid of Luke’s (1967) variational principle, which models the evolution of nonlinear water waves in intermediate depth over a general bathymetry. The vertical structure of the wave field is exactly represented by means of a local-mode series expansion of the wave potential, Athanassoulis & Belibassakis (2000). This series contains the usual propagating and evanescent modes, plus two additional modes, the free-surface mode and the sloping-bottom mode, enabling to consistently treat the non-vertical end-conditions at the free-surface and the bottom boundaries. The system fully accounts for the effects of non-linearity and dispersion. b.16 Athanassoulis, G.A., Belibassakis, K.A., Stefanakos, Ch.N, 2002, Wave power prediction in nearshore areas based on offshore wave information. A case study, 21st IASTED, Power and Energy Systems (EuroPES 2002), Crete, Greece. In the present work, a methodology for the calculation of the wave conditions in nearshore/ coastal areas is applied to the prediction of the corresponding wave energy potential. The methodology has been developed in the framework of the EUROWAVES project, and is based on transforming the available offshore wave information to any nearshore/coastal site of interest, using the third-generation, phase-averaged, nearshore wave model (SWAN, Booij et al 1999, Ris et al 1999), and exploiting available geographical information concerning the bathymetry and coastline of the area under consideration. Numerical results are presented demonstrating the application of the above methodology to nearshore and coastal sites of the Greek Seas. b.17 Athanassoulis, G.A., Belibassakis, 2003, Rapidly-convergent local-mode representations for wave propagation and scattering in curved-boundary waveguides, 6th Int. Conference on Mathematical and Numerical Aspects of Wave Propagation (WAVES 2003), organized by SIAM and INRIA, Finland A new general method for treating wave propagation and scattering problems in partially limited domains with curved boundaries is established, based on an enhanced local-mode series, which includes an additional term accounting for the effects of the curved boundary. The additional mode provides an implicit summation of the slowly convergent part O(n-2) of the local-mode series, rendering the remaining part to converge much faster, like O(n-4), where n is the mode order.

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b.18 Athanassoulis, G.A., Belibassakis, K.A., Georgiou Y., 2003, Transformation of the Point Spectrum over Variable Bathymetry Regions, 13th Intern. Offshore and Polar Conference and Exhibition, ISOPE2002, Honolulu, Hawaii, USA. The problem of transformation of the spectrum of an incident wave system over a region of strongly varying bottom topography is studied, in the context of linear theory. The present work focuses on cases where the typical wave length and the characteristic length of the bottom profile variations are comparable, and the waves propagate in intermediate-to-shallow water depth. The Consistent Coupled-Mode Model (Athanassoulis and Belibassakis, 1999) is exploited for the calculation of the linear transfer function, connecting the incident wave with the wave conditions at each point in the field. Our model takes into account propagation, reflection and diffraction phenomena. The present approach permits the consistent transformation of the full incident wave spectrum over variable bathymetry regions and the calculation of the spatial evolution of point spectra of all interesting wave quantities (free surface elevation, velocity, pressure), at every point in the domain. The present approach can be extended to treat obliquely incident waves, as well as weakly non-linear waves. b.19 Barstow, S., Mørk, G., Lønseth L, Schjølberg, P., Machado, U., Athanassoulis, G., Belibassakis, K., Gerostathis, T., Stefanakos, Ch., Spaan, G., 2003, WORLDWAVES: Fusion of data from many sources in a user-friendly software package for timely calculation of wave statistics in global coastal waters, 13th Intern. Offshore and Polar Conference and Exhibition, ISOPE2003, Honolulu, Hawaii, USA. In the absence of long term wave data collected at a site of interest, the calculation of reliable wave statistics at a coastal site requires various data sets to be assembled, including temporal long term representative directional wave data offshore of the site, in addition to bathymetric and coastline data. Further, a suitable wave model, capable of modelling the transfer of the offshore conditions to the site, is required, incorporating the relevant shallow water wave phenomena. WORLDWAVES simplifies and speeds up the modelling of wave conditions in coastal waters by integrating the following under a single Matlab toolbox: High quality long-term wave data offshore all global coasts; worldwide bathymetric and coastline data; SWAN and backward raytracing wave models; sophisticated offshore and nearshore wave statistics toolboxes with tabular and graphical presentations, including a facility to export ASCII time series data at offshore or inshore locations; a geographic module with easy zooming to any area worldwide; tools to set up model grids and displaying and editing bathymetry and coastline; a facility for the import of user offshore data and export of inshore time series data. In this paper we describe the design and implementation of WorldWaves including the fusion of satellite, model and buoy wave and wind data in the global offshore database. b.20 Barstow, S., Mørk, G., Lønseth L, Schjølberg, P., Machado, U., Athanassoulis, G., Belibassakis, K., Gerostathis, T., Stefanakos, Ch., Spaan, G., 2003, WORLDWAVES: High quality coastal and offshore wave data within minutes for any global site, 22nd International Conference on Offshore Mechanics and Arctic Engineering, OMAE2003, Cancun, Mexico. There has been a growing demand for reliable information on the wave conditions, in particular at coastal sites, as a result of increased utilisation of the coastal zone to a multitude of activities including various shoreline developments related to transportation, tourism, fish farming and recently wind and wave energy industries. This trend is likely to continue. Reliable data is also needed with respect to the management and protection of these often fragile environments. Many of those concerned with these wave-impacted environments still use antiquated data sources, usually from offshore waters as, in the absence of long term wave data collected at the site of interest, the calculation of reliable wave statistics at a coastal site is a complicated, time consuming and expensive business, requiring various data sets to be assembled. WORLDWAVES simplifies and speeds up the modelling of wave conditions in coastal waters by integrating the following under a single Matlab toolbox: High quality long-term wave data offshore all global coasts; worldwide bathymetric and coastline data; SWAN and backward raytracing wave models; sophisticated offshore and nearshore wave statistics toolboxes with tabular and graphical presentations, including a facility to export ASCII time series data at offshore or inshore locations; a geographic module with easy zooming to any area worldwide; tools to set up model grids and display and edit bathymetry and coastline; a facility for the import of user offshore data and export of inshore time series data. In this paper we describe the design and implementation of WorldWaves including the fusion of satellite, model and buoy wave and wind data in the global offshore database and the new raytracing model.

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b.21 Belibassakis K.A. and Athanassoulis G.A., 2004, Hydroelastic responses of Very Large Floating Structures lying over variable bathymetry regions, 14th Intern. Offshore and Polar Conference and Exhibition, ISOPE2004, Toulon, France. In the present work, a coupled-mode technique is developed and applied to the hydroelastic analysis of very large floating platforms of shallow draft lying over variable bathymetry regions. Under the assumption of small-amplitude incident waves and small deflections, the linearised water-wave equations have been used, and the shallow-draft platform has been modelled as a thin elastic plate. In order to consistently treat the wave field beneath the elastic floating structure, the present approach is based on appropriate extensions of the coupled-mode model developed by Athanassoulis & Belibassakis (1999) for waves propagating in variable bathymetry regions, which is free of any mild-slope assumption concerning the bottom boundary. Numerical results concerning floating structures lying over flat and sloping beds are comparatively presented, and the effects of the bottom slope on the hydroelastic responses of the system are examined and discussed. Some of the important features of the present approach is that it can be further extended to treat the 3D problem and to include the effects of weak nonlinearity. b.22 Belibassakis K.A. and Athanassoulis G.A., 2004, A Coupled-Mode technique for wave-current interaction in variable bathymetry regions, 14th Intern. Offshore and Polar Conference and Exhibition, ISOPE2004, Toulon, France. A coupled-mode technique for wave-current interaction is presented, with application to the problem of wave scattering by steady currents in variable bathymetry regions, and current variations on various scales. We consider obliquely incident waves on a horizontally non-homogeneous current in a variable-depth strip, which is characterized by straight and parallel bottom contours. The flow associated with the current is assumed to be parallel to the bottom contours (along-axis current) and it is considered to be known. In a finite subregion containing the bottom irregularity we assume an arbitrary horizontal current structure. Outside this region, the current is assumed to be uniform (or zero). At a first-order of approximation the wave flow is assumed to be irrotational, i.e. the vorticity of the total field is the same with the vorticity associated with the current. Then, restricting ourselves to linear, monochromatic (harmonic) waves of absolute frequency ω, the wave potential, including the scattering effect by the current, is obtained as a solution to the modified Helmholtz equation, subject to the free-surface boundary condition formulated with respect to the intrinsic frequency, the bottom boundary condition, and the conditions at infinity. Based on an appropriate variational principle, in conjunction with a rapidly-convergent local-mode series expansion of the wave field in a finite subregion containing the current variation and the bottom irregularity, a coupled-mode system is obtained that can be considered as a generalization of the one derived by Athanassoulis & Belibassakis (1999). The present approach can be considered as an extension of the works by Smith (1983, 1987), and some of its main features are that it can be further elaborated to treat lateral discontinuities (e.g. vertical vortex sheets) and more general vertical current profiles with cross-jet component, and to include the effects of weak nonlinearity. b.23 Belibassakis K.A. and Athanassoulis G.A., Hydroelastic behavior of floating flexible plates on surface gravity waves with the effects of variable bathymetry, 7th National Congress on Mechanics HSTAM 2004, June 24-26, 2004, Chania-Crete, Greece. A coupled-mode technique is developed and applied to the hydroelastic analysis of flexible plates on surface gravity waves, modelling very large floating platforms of shallow draft lying over variable bathymetry regions. Under the assumption of small-amplitude incident waves and small deflections, the linearised equations have been used. In order to consistently treat the wave field beneath the elastic floating plate, the present approach is based on appropriate extensions of the coupled-mode model developed by Athanassoulis & Belibassakis [1] for waves propagating in variable bathymetry regions, which is free of any mild-slope assumption concerning the bottom boundary. Numerical results concerning floating structures lying over flat and sloping beds are presented, and the effects of the bottom slope on the hydroelastic responses of the system are discussed. An important feature of the present approach is that it can be further extended to include the effects of weak nonlinearity. b.24 Belibassakis, K.A., 2004, Hydrodynamic analysis of floating bodies in variable bathymetry regions, 1st Intern. Conference from Scientific Computing to Computation Engineering IC-SCCE, Athens, Greece, 2004.

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The interaction of free-surface gravity waves with floating bodies, in water of intermediate depth with a general bathymetry, is a mathematically interesting problem finding important applications, as e.g., in evaluating ship and structure performance operating in nearshore and coastal waters. Moreover, pontoon-type floating bodies of relatively small dimensions find applications as coastal protection devices (floating breakwaters) and are frequently used as small boat marinas. In most applications, the water depth is assumed to be constant, which is practically valid in the case when depth variations are small. However, in cases involving the operation of ships and floating structures in coastal waters, the variations of bathymetry may have a significant effect. In the present work, a hybrid model, based on the consistent coupled-mode theory developed by Athanassoulis & Belibassakis (1999) and extended to 3D by Belibassakis et al (2001), which is free of any mild-slope assumption, in conjunction with a boundary integral representation of the wave field in the vicinity of the floating body, is used to treat the problem of hydrodynamic analysis of floating bodies in variable bathymetry regions. Numerical results are presented concerning floating bodies of simple geometry lying over sloping beds. With the aid of systematic comparisons, the effects of bottom slope on the hydrodynamic characteristics (hydrodynamic coefficients and responses) are presented and discussed. b.25 Belibassakis, K.A., Stephanakos, C.N, Bratsos, A., Prospathopoulos, A., 2004, Numerical simulation of weakly nonlinear wave propagation in variable bathymetry regions, Intern. Conference of Numerical Analysis and Applied Mathematics (ICNAAM 2004), Chalkis, Greece, 10-14 Sept. 2004. In the present work, we study and optimize a numerical scheme, to simulate weakly-nonlinear wave propagation over variable bathymetry regions, both in shallow-water and intermediate water depth. In order to test and validate the optimized numerical model, comparisons are presented between our results, experimental measurements [S. Beji and J.A. Battjes, Coastal Engng. 23, 1-16, 1994], the consistent coupled-mode model [G.A. Athanassoulis and K.A. Belibassakis, J. Fluid Mech. 389, 275-301, 1999] which is appropriate for waves in intermediate water depth, and the predictions by the commercial software package MIKE 21 BW, developed by DHI [MIKE 21 BW, User Guide, in: MIKE 21, Wave Modelling, DHI, 2002], for various test cases. b.26 Belibassakis, K.A., 2005, Hydrodynamic Analysis of Floating Bodies in General Bathymetry, 24th International Conference on Offshore Mechanics and Arctic Engineering, OMAE2005, Halkidiki, Greece. A hybrid technique, based on the coupled-mode theory developed by Athanassoulis & Belibassakis (1999) and extended to 3D by Belibassakis et al (2001) and Belibassakis & Athanassoulis (2004), which is free of any mild-slope assumption, is used, in conjunction with a boundary integral representation of the near field in the vicinity of the body, to treat the problem of hydrodynamic analysis of floating bodies in the presence of variable bathymetry. Numerical results are presented concerning floating bodies of simple geometry lying over sloping seabeds. With the aid of systematic comparisons, the effects of bottom slope on the hydrodynamic characteristics (hydrodynamic coefficients and responses) are illustrated and discussed. b.27 Stefanakos, Ch., Belibassakis, K.A., 2005, Nonstationary Stochastic Modelling Of Multivariate Long-Term Wind And Wave Data, 24th International Conference on Offshore Mechanics and Arctic Engineering, OMAE2005, Halkidiki, Greece. In the present work, a nonstationary stochastic model, which is suitable for the analysis and simulation of multivariate time series of wind and wave data, is being presented and validated. This model belongs to the class of periodically correlated stochastic processes with yearly periodic mean value and standard deviation (periodically correlated or cyclostationary stochastic process). First, the time series is appropriately transformed to become Gaussian using the Box-Cox transformation. Then, the series is decomposed, using an appropriate seasonal standardization procedure, to a periodic (deterministic) mean value and a (stochastic) residual time series multiplied by a periodic (deterministic) standard deviation. The periodic components are estimated using appropriate time series of monthly data. The residual stochastic part, which is proved to be stationary, is modelled as a VARMA process. This way the initial process can be given the structure of a multivariate periodically correlated process. The present methodology permits a reliable reproduction of available information about wind and wave conditions, which is required for a number of applications.

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b.28 Gerostathis, T., Belibassakis, K.A., Athanassoulis, G.A., 2005, A Coupled-Mode, Phase-Resolving Model For The Transformation Of Wave Spectrum Over Steep 3D Topography. A Parallel-Architecture Implementation, 24th International Conference on Offshore Mechanics and Arctic Engineering, OMAE2005, Halkidiki, Greece. The problem of transformation of the directional spectrum of an incident wave system over a region of strongly varying three-dimensional bottom topography is studied, in the context of linear theory. The Consistent Coupled-Mode Model (Athanassoulis and Belibassakis 1999, Belibassakis et al 2001) is exploited for the calculation of the linear transfer function, connecting the incident wave with the wave conditions at each point in the field. This model takes fully into account reflection, refraction and diffraction phenomena. The present approach permits the consistent transformation of any incident directional wave spectrum over a variable bathymetry region and the calculation of the spatial evolution of point spectra of all interesting wave quantities (free surface elevation, velocity, pressure), at every point in the domain. This approach can be extended to treat weakly non-linear waves. b.29 Belibassakis, K.A., 2005, Propagation of water waves through shearing currents in general bathymetry International Maritime Association of the Mediterranean, Maritime Transportation and Exploitation of Ocean and Coastal Resources, IMAM2005, Lisbon, Portugal A coupled-mode model is presented for wave-current-seabed interaction, with application to the problem of wave scattering by steady shearing currents in variable bathymetry regions. We consider obliquely incident waves on a horizontally non-homogeneous current in a variable-depth strip, which is characterized by straight and parallel bottom contours. The flow associated with the current is assumed to be parallel to the bottom contours and it is considered to be known. In a finite subregion containing the bottom irregularity, we assume an arbitrary horizontal current structure. Outside this region, the current is assumed to be uniform (or zero). Based on a variational principle, in conjunction with a rapidly-convergent local-mode series expansion of the wave pressure field in a finite subregion containing the current variation and the bottom irregularity, a coupled-mode system is obtained. The present model can be considered as an extension of the works by Smith (1983, 1987) and McKee (1987,1996), and it can be further elaborated to treat more general current profiles with vertical structure and cross-jet component, and to include the effects of weak nonlinearity. b.30 Belibassakis, K.A., Hatzikostandis, G.K, Theotokatos G,. Stefanakos Ch.N., Sarantopoulos S., Gerostathis Th., Georgiou Y.G, New challenges in the education of Naval Architects in TEI of Athens, WSEAS Intern. Conference on Engineering Education, Athens, Greece, July 8-10, 2005. In this work we describe recent advances in the curriculum offered and in the research conducted by the Department of Shipbuilding, School of Technological Applications at the Technological Educational Institute of Athens. The developments include the amendment of the curriculum by new specialized courses of the Naval Architecture and Marine Engineering discipline, as well as current research projects carried out by members of the Department, all funded in the framework of Operational Programme for Education and Initial Vocational Training (EPEAEK), coordinated by the Greek Ministry of Education and the European Union. b.31 Bratsos, A., Belibassakis, K.A., Natsis, D.G., Papadopoulos, D.P., 2005, On the numerical modeling of a shallow water equation, 17th IMACS World Congress on Scientific Computation, Applied Mathematics and Simulation, 11-15 July 2005, Paris, France (paper T1-I-28-0176). An implicit finite-difference method is presented for the numerical solution of the two dimensional Boussinesq-type set of equations as those were introduced by Peregrine (1967). The application of the finite-difference scheme results in an initial value problem and it is proposed the unknown quantities to be evaluated implicitly by solving a linear system of equations. The numerical treatment of the system is briefly discussed, while numerical results are the subject of a following work. b.32 Bratsos A. G., Famelis I. Th. and K. A. Belibassakis, 2005, An implicit numerical method for a shallow water equation in 2+1 dimensions, International Conference of Numerical Analysis and Applied Mathematics, ICNAAM2005, Rhodes, Greece, 16-20 Sept. 2005, Wiley-VCH, pp. 103-106. An implicit finite-difference method is presented for the numerical solution of the two-dimensional Boussinesq-type set of equations as those were introduced by Peregrine (1967). The application of the

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finite-difference scheme results in an initial value problem and it is proposed the unknown quantities to be evaluated implicitly by solving a linear system of equations. b.33 Athanassoulis, G.A., Belibassakis, K.A., 2005, Nonlinear water-wave problem: A consistent coupled-mode reformulation and derivation of families of travelling wave solutions, 7th Int. Conference on Mathematical and Numerical Aspects of Wave Propagation (WAVES 2005), Brown University, USA. A non-linear coupled-mode system of horizontal equations is derived with the aid of Luke’s (1967) variational principle, which models the evolution of nonlinear water waves in intermediate depth and over a general bathymetry, and applied to numerical investigation of travelling wave solutions in constant depth. The vertical structure of the wave field is represented by means of a local-mode series expansion of the wave potential, Athanassoulis & Belibassakis (2000, 2002). This series contains the usual propagating and evanescent modes, plus two additional modes, the free-surface mode and the sloping-bottom mode, enabling to consistently treat the non-vertical end-conditions at the free-surface and the sloping bottom boundaries. The system fully accounts for the effects of non-linearity and dispersion. b.34 Belibassakis K.A. and Athanassoulis G.A., 2006, A coupled mode technique for the run-up of non-breaking dispersive waves on plane beaches, 25th International Conference on Offshore Mechanics and Arctic Engineering, OMAE2006, Hamburg, Germany. A coupled-mode model is developed and applied to the transformation and run-up of dispersive water waves on plane beaches. The present work is based on the consistent coupled-mode theory for the propagation of water waves in variable bathymetry regions, developed by Athanassoulis & Belibassakis (1999) and extended to 3D by Belibassakis et al (2001), which is suitably modified to apply to a uniform plane beach. The key feature of the coupled-mode theory is a complete modal-type expansion of the wave potential, containing both propagating and evanescent modes, being able to consistently satisfy the Neumann boundary condition on the sloping bottom. Thus, the present approach extends previous works based on the modified mild-slope equation in conjunction with analytical solution of the linearised shallow water equations, see, e.g., Massel & Pelinovsky (2001). Numerical results concerning non-breaking waves on plane beaches are presented and compared with exact analytical solutions, Wehausen & Laitone (1960, Sec. 18). Also, numerical results are presented concerning the run-up of non-breaking solitary waves on plane beaches and compared with the ones obtained by the solution of the shallow-water wave equations, Synolakis (1987), Li & Raichlen (2002), and experimental data, Synolakis (1987). b.35 Xiros N.I., Belibassakis K.A., Athanassoulis G.A., 2006, Modeling and Assessment of the Underwater Acoustic Channel for Submerged End-Users Positioning Information Transmission and Applications, 16th Intern. Offshore and Polar Conference and Exhibition, ISOPE2006, San Fransisco. When performing underwater operations, submerged personnel, vessels and devices need constantly updated positioning information. A constellation of sea surface crafts of either conventional or buoy type, broadcasting broadband acoustic signals underwater, allows establishing positioning service to submerged end-users. This work investigates the underwater acoustic channel when used for transmission of positioning information. This task includes the appropriate description of the underwater medium and the impairments involved, e.g. ambient noise, chromatic dispersion, multipath and Doppler effects etc. In this end, time-frequency, time-scale, and frequency-scale representations of time-varying channels provide certain advantages, including a derivation of the rake receiver. b.36 Gkikas G.D., Xiros N.I., Athanassoulis G.A. and Belibassakis K.A., 2006, A nonlinear model for Oscillating Water Column analysis, design and control, 16th Intern. Offshore and Polar Conference and Exhibition, ISOPE2006, San Francisco. A model for the energy exchanges involved in OWC power-plants is proposed. The model is using data series generated by numerical codes developed on the basis of relative physical principles. The ocean wave field and the oscillating water column are modeled according to linear water wave theory as a waveguide excited at both ends. The thermodynamic process inside the chamber is modeled with a control-volume approach. Then by applying identification techniques for linear and nonlinear systems, the corresponding operator representations are obtained in the frequency domain. A closed-loop is finally constructed which may find use in analysis and synthesis of OWC systems.

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b.37 Athanassoulis, G.A., Belibassakis, K.A., Gerostathis, T., 2006, Wave data along ship routes in the Mediterranean Sea, 9th Int Conf. on Stability od Ships and Ocean Vehicles, STAB2006, Rio de Janeiro, Brazil. The calculation of reliable wave statistics for the probabilistic assessment of ship stability requires various data sets to be assembled, including temporal long term representative directional wave and wind data, for a set of geographical points distributed along the route. In the present paper we give a description of the above data available in the Mediterranean Sea, and their exploitation for the long-term probabilistic assessment of ship stability. We also discuss the problems and consequent limitations associated to each source of data. b.38 Athanassoulis, G.A., Belibassakis, K.A., 2006, A new unified theory for nonlinear steady travelling waves in constant, but arbitrary, depth, 7th Intern. Conference on Hydrodynamics, ICHD 2006, Ischia, Italy. A non-linear coupled-mode system of equations on the horizontal plane is derived with the aid of Luke’s (1967) variational principle, which models the evolution of nonlinear water waves in intermediate depth and over a general bathymetry. The vertical structure of the wave field is exactly represented by means of a local-mode series expansion of the wave potential, Athanassoulis & Belibassakis (2002). This series contains the usual propagating and evanescent modes, plus two additional modes, the free-surface mode and the sloping-bottom mode, enabling the consistent treatment of the non-vertical end-conditions at the free-surface and the bottom boundaries. The coupled-mode system fully accounts for the effects of non-linearity and dispersion. The main features of the present approach are the following: (i) various standard models of water-wave propagation are recovered by appropriate simplifications of the coupled-mode system, and (ii) a small number of modes are enough for a precise numerical solution, provided that the two new modes (the free-surface and the sloping-bottom ones) are included in the local-mode series. In the present work, the coupled-mode system is applied to the numerical derivation and investigation of families of steady travelling wave solutions in constant depth regions, corresponding to various water depths, ranging from intermediate to shallow wave conditions. b.39 Belibassakis, K.A., Gerostathis, T., Athanassoulis, G.A., 2007, A phase-resolving, coupled-mode model for wave-current-seabed interaction over steep 3D bottom topography. Parallel architecture implementation, 17th Intern. Offshore and Polar Conference and Exhibition, ISOPE2007, Lisbon A phase-resolving, coupled-mode model is developed for the wave-current-seabed interaction problem, with application to wave scattering by steady currents over steep three-dimensional bottom topography. The vertical distribution of the wave potential is represented by a series of local vertical modes. This series consists of the vertical eigenfunctions associated with the propagating and all evanescent modes, plus an additional mode, accounting for the bottom boundary condition when the bottom slope is not negligible, as thoroughly discussed in Athanassoulis & Belibassakis (1999). Using the above representation in conjunction with a variational principle, Luke (1967), the problem is reduced to a coupled system of differential equations on the horizontal plane. If only the propagating mode is retained in the vertical expansion of the wave potential, and after additional simplifications, the above coupled-mode system is reduced to the one-equation model derived by Kirby (1984) with application to the problem of wave-current interaction over slowly varying topography. To treat the problem of wave-current-seabed interaction in unbounded domain, the present model is applied in conjunction with open sea/lateral boundary conditions, see, e.g., Chen et al (2005). The present system is discretized by using a second-order finite difference scheme and numerically solved by means of a parallel implementation, developed using the message passing programming paradigm on a commodity computer cluster; see, e.g., Gerostathis et al (2005). Thus, direct numerical solution of the present system is made feasible for realistic domains corresponding to areas with size of the order of several kilometers. The analytical structure of the present model facilitates its extension to treat non-linear waves, and it can be further elaborated to study wave propagation over random bottom topography and currents. b.40 Belibassakis, K.A., Athanassoulis, G.A., 2007, A coupled-mode technique for the prediction of wave-induced set-up in variable bathymetry domains and groundwater circulation in permeable

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beaches, 17th Intern. Offshore and Polar Conf. and Exhibition, ISOPE2007, Lisbon In the present work a complete phase-resolving wave model is coupled with an iterative solver of the mean-flow equations, permitting an accurate calculation of wave-induced set-up in intermediate and shallow water environments with possibly steep bathymetric variations. The wave model is based on the consistent coupled-mode system for the propagation of water waves in variable bathymetry regions, developed by Athanassoulis & Belibassakis (1999) and extended to 3D by Belibassakis et al (2001). This model improves the predictions of the mild-slope equation(s), permitting accurate treatment of wave propagation in regions with steep bottom slope and/or large curvature. In addition, it supports the correct calculation of wave velocity up to the bottom boundary. The coupled-mode model has been further extended to include the effects of energy dissipation from bottom friction and wave breaking, which are important for the accurate calculation of radiation stresses on decreasing depth. Furthermore, it has been used in conjunction with the mean flow equations to predict wave-induced set up and flow in closed and open domains. Finally, the resulting phase-averaged mean-pressure has been applied to calculate the induced groundwater circulation on a permeable beach, in the set-up region. Under the assumption that the groundwater flow is in the Darcy law regime, in the case of a stationary mean flow, the porous flow velocity can be obtained in terms of the pressure gradient. In this case, Massel (2001), the problem concerning groundwater circulation is governed by the Laplace’s equation on the pressure, forced by Dirichlet data specified by the excess pressure on the sea bottom that is induced by the mean flow. b.41 Belibassakis, K.A., Gerostathis, T., Athanassoulis, G.A., 2007, Calculation of wave-induced set-up in variable bathymetry regions and groundwater flow in permeable beaches by a coupled-mode method, 8th HSTAM International Congress on Mechanics, Patras, Greece. A phase-resolving wave model is coupled with an iterative solver of the mean-flow equations and applied to the calculation of wave-induced set-up in intermediate and shallow water environments with general bathymetric variations. The wave model is based on the consistent coupled-mode model for the propagation of water waves in variable bathymetry regions, developed by Athanassoulis & Belibassakis (1999). This model improves the predictions of the mild-slope equation, permitting accurate treatment of wave propagation in regions with steep bottom slope and/or large curvature. In addition, it supports the correct calculation of wave velocity up to the bottom boundary. The above model has been further extended to include the effects of bottom friction and wave breaking, which are important for the calculation of radiation stresses on decreasing depth. Furthermore, it has been used in conjunction with the mean flow equations to predict wave-induced set up in open and closed domains. Finally, the resulting phase-averaged mean-pressure on the bottom has been used to calculate induced groundwater circulation in permeable beach in the set-up region, assuming that the groundwater flow is in the Darcy law regime. In this case, the problem concerning groundwater circulation is governed by the Laplace equation, forced by Dirichlet data for the excess pressure on the sea bottom induced by the mean flow. b.42 Belibassakis K.A., Stefanakos, C.N., Georgiou, Y., 2007, Extreme value predictions on decreasing depth by means of a nonlinear wave transformation model, 26th International Conference on Offshore Mechanics and Arctic Engineering, OMAE2007, San Diego, USA. In the present work a weakly nonlinear wave model originally developed by Rebaudengo Landò et al (1996) is applied to the transformation of wave spectra from offshore to nearshore, and subsequently, it has been systematically applied to the derivation of long-term time series of spectral wave parameters on decreasing depth from corresponding offshore wave data. The derived long-term series of nearshore parameters have been used as input to a new method, recently developed by Stefanakos & Athanassoulis (2006), for calculating return periods of various level values from nonstationary time series data. The latter method is based on a new definition of the return period, that uses the MEan Number of Upcrossings of the level *x (MENU method), and it has been shown to lead to predictions that are more realistic than traditional methods. To examine the effects of bottom topography on the nearshore extreme value predictions, Roseau (1976) bottom profiles have been used for which analytical expressions are available concerning the reflection and transmission coefficients. A parametric (JONSWAP) model is used to synthesize offshore spectra from integrated parameters, which are then linearly transformed based on the previous transmission coefficient to derive first-order nearshore wave spectra. Second-order random sea states have been simulated by following the approach of Hudspeth & Chen (1979) (see also Langley 1987, Lando et al 1996), exploiting the quadratic transfer functions on decreasing depth to calculate the second-order nearshore spectra.

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Finally, wave parameters are extracted from the nearshore spectra by calculating the first few moments. b.43 Belibassakis K.A., Th.P. Gerostathis and Athanassoulis G.A., 2007, A coupled-mode technique for the prediction of wave-induced set-up and mean flow in variable bathymetry domains 26th Int. Conference on Offshore Mechanics and Arctic Engineering, OMAE2007, San Diego, USA. In the present work, a complete, phase-resolving wave model is coupled with an iterative solver of the mean-flow equations in intermediate and shallow water depth, permitting an accurate calculation of wave set-up and wave-induced current in intermediate and shallow water environment with possibly steep bathymetric variations. The wave model is based on the consistent coupled-mode system of equations, developed by Athanassoulis & Belibassakis (1999) for the propagation of water waves in variable bathymetry regions. This model improves the predictions of the mild-slope equation, permitting the treatment of wave propagation in regions with steep bottom slope and/or large curvature. In addition, it supports the consistent calculation of wave velocity up to and including the bottom boundary. The above wave model has been further extended to include the effects of bottom friction and wave breaking, which are important factors for the calculation of radiation stresses on decreasing depth. The latter have been used as forcing terms to the mean flow equations in order to predict wave-induced set up and mean flow in open and closed domains. Numerical results obtained by the present model are presented and compared with predictions obtained by the mild-slope approximation (Massel & Gourlay 2000), and experi-mental data (Gourlay 1996). b.44 Belibassakis, K.A., Gerostathis, T., Athanassoulis, G.A., 2007, Wave-current systems in variable bathymetry regions, 12th International Congress of the International Maritime Association of the Mediterranean IMAM2007, Varna Boulgaria In the present work a new coupled-mode model, recently developed by the authors is applied to the wave-current-seabed interaction problem, with application to wave scattering by steady currents over three-dimensional bottom topography. The vertical structure of the wave field is represented by a series of local vertical modes, consisting of the propagating and all evanescent modes, plus an additional mode, accounting for the bottom boundary condition on the sloping bottom; see, e.g., Belibassakis et al (2001). If only the propagating mode is retained in the vertical expansion of the wave potential, and after additional simplifications, the above coupled-mode system reduces to the one-equation model earlier derived and studied by Kirby (1984). The present system is numerically solved by means of a parallel implementation, developed using the message passing programming paradigm on a commodity computer cluster; see, e.g., Gerostathis et al (2005). Thus, direct numerical solution of the present system is made feasible for realistic domains corresponding to areas with size of the order of several kilometres, facilitating the transformation of wave energy spectra in the presence of variable bottom topography and currents. b.45 Belibassakis, K.A., Chatzikostandis, G, Georgiou Y., 2007, Optimisation of naval technology for novel oil-spill combating technique, 12th International Congress of the International Maritime Association of the Mediterranean IMAM2007, Varna Boulgaria. Sea pollution by oil-spills is a huge environmental and economical problem, especially in regions with increased ship traffic. Despite considerable research, current oil-slick anti-pollution technologies have not been proved to be totally efficient. One technique is based on the method of magnetic separation, using an oleophilic, porous, magnetic material having density lower than the water. This material, after sprayed in granular form over the oil spill, absorbs the oil which subsequently can be collected from vessels equipped with appropriate magnetic means. A prototype, single-hull vessel, equipped with magnetic collection system has been designed, constructed and successfully tested. However, it is shown that a twin hull (catamaran-type) provides optimal solution, especially concerning the operability of the ship in the open sea and in the nearshore/coastal environment. The present analysis has been supported by new models for offshore- to-nearshore wave propagation and the hydrodynamic analysis of ships and floating units in variable bathymetry. b.46 Athanassoulis G.A., Belibassakis K.A., 2008, A unified coupled-mode approach to nonlinear waves in finite depth. Potential flow. 27th International Conference on Offshore Mechanics and Arctic Engineering, OMAE2008, Estoril, Portugal.

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A non-linear coupled-mode system of horizontal equations is presented, as derived from Luke’s (1967) variational principle, which models the evolution of nonlinear water waves in intermediate depth over a general bottom topography. The vertical structure of the wave field is represented by means of a complete local-mode series expansion of the wave potential. This series contains the usual propagating and evanescent modes, plus two additional terms, the free-surface mode and the sloping-bottom mode, enabling to consistently treat the non-vertical end-conditions at the free-surface and the bottom boundaries. The present coupled-mode system fully accounts for the effects of non-linearity and dispersion, and has the following main features: (i) various standard models of water-wave propagation are recovered by appropriate simplifications, and (ii) it exhibits fast convergenge, and thus, a small number of modes (up to 5) are usually enough for the precise numerical solution, provided that the two new modes (the free-surface and the sloping-bottom ones) are included in the local-mode series. In the present work, the coupled-mode system is applied to the numerical investigation of families of steady travelling wave solutions in constant depth, corresponding to a wide range of water depths, ranging from intermediate to shallow-water wave conditions and its results are compared vs. Stokes and cnoidal wave theories, respectively. Also, numerical results are presented for waves propagating over variable bathymetry regions and compared with second-order Stokes theory and experimental data. b.47 Belibassakis, K.A., Gerostathis, T., Athanassoulis, G.A., 2008, A weakly nonlinear couple-mode model for wave-current-seabed interaction over general bottom topography, 27th International Conference on Offshore Mechanics and Arctic Engineering, OMAE2008, Estoril, Portugal. A weakly nonlinear, coupled-mode model is developed for the wave-current-seabed interaction problem, with application to wave scattering by steady currents over general bottom topography. Based on previous work by the authors (Athanassoulis & Belibassakis 1999, Belibassakis et al 2001), the vertical distribution of the scattered wave potential is represented by a series of local vertical modes containing the propagating mode and all evanescent modes, plus an additional term accounting for the bottom boundary condition when the bottom slope is not negligible. Using the above representation, in conjunction with Luke’s (1967) variational principle, the wave-current-seabed interaction problem is reduced to a coupled system of differential equations on the horizontal plane. If only the propagating mode is retained in the vertical expansion of the wave potential, and after simplifications, the present system is reduced to an one-equation model compatible with Kirby’s (1984) mild-slope model with application to the problem of wave-current interaction over slowly varying topography. The present coupled-mode system is discretized on the horizontal plane by using a second-order finite difference scheme and numerically solved by iterations. Numerical results are presented for two representative test cases, demonstrating the importance of the first evanescent modes and the sloping-bottom mode. The analytical structure of the present model facilitates its extension to treat fully non-linear waves, and it can be further elaborated to study wave propagation over random bottom topography and general currents. b.48 Belibassakis, K.A., Athanassoulis, G.A., 2008, A coupled-mode approach to nonlinear waves in finite depth. Viscous bottom boundary-layer flow, 8th Intern. Conference on Hydrodynamics, ICHD 2008, Nantes, France. A weakly dissipative free-surface flow model is presented, based on the potential flow approach previously developed by the authors (Athanassoulis & Belibassakis 2002, 2006). The potential flow model is derived with the aid of Luke's (1967) variational principle, in conjunction with a complete vertical expansion, leading to a non-linear coupled-mode system of horizontal equations. The latter coupled-mode system models the evolution of nonlinear water waves over a general bathymetry in intermediate and shallow water depth conditions. The consistent coupled mode system has been applied to numerical investigation of families of steady travelling wave solutions in constant depth (Athanassoulis & Belibassakis 2007) showing good agreement with known solutions both in the Stokes and the cnoidal wave regimes. In the present work, the above coupled-mode model is linked with laminar bottom boundary layer equations, permitting the investigation of viscous effects on wave propagation up to leading-order. b.49 Belibassakis, K.A., Athanassoulis, G.A., 2009, A fast convergent modal-expansion of the wave potential with application to the hydrodynamic and hydroelastic analysis of floating bodies in general bathymetry,28th International Conference on Offshore Mechanics and Arctic Engineering, OMAE2009, Hawaii.

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A non-linear coupled-mode system of horizontal equations has been derived with the aid of Luke’s (1967) variational principle, modelling the evolution of nonlinear water waves in intermediate depth and over a general bathymetry Athanassoulis & Belibassakis (2002, 2008). Following previous work by the authors in the case of linearised water waves (Athanassoulis & Belibassakis 1999), the vertical structure of the wave field is exactly represented by means of a local-mode series expansion of the wave potential. This series contains the usual propagating and evanescent modes, plus two additional modes, the free-surface mode and the sloping-bottom mode, enabling to consistently treat the non-vertical end-conditions at the free-surface and the bottom boundaries. The coupled-mode system fully accounts for the effects of non-linearity and dispersion. The main feature of this approach that a small number of modes (of the order of 5-6) are enough for the precise numerical solution, provided that the two new modes (the free-surface and the sloping-bottom ones) are included in the local-mode series. The consistent coupled-mode system has been applied to numerical investigation of families of steady nonlinear travelling wave solutions in constant depth (Athanassoulis & Belibassakis 2007) showing good agreement with known solutions both in the Stokes and the cnoidal wave regimes. In the present work we focus on the hydroelastic analysis of floating bodies lying over variable bathymetry regions, with application to the non-linear scattering of water waves by large floating structures (of VLFS type or ice sheets) characterised by variable thickness (draft), flexural rigidity and mass distributions, modelled as thin plates of variable thickness, extending previous approaches (see, e.g., Porter & Porter 2004, Belibassakis & Athanassoulis 2005, 2006, Bennets et al 2007). b.50 Belibassakis, K.A., Athanassoulis, G.A., 2009, A coupled-mode model with application to wave scattering by VLFS or ice sheets of varying thickness over general bottom topography , 5th Int. Conf. on Hydroelasticity in Marine Technology, Southapton. In the present work, the coupled-mode model developed by the authors (Belibassakis & Athanassoulis 2005, 2006) is extended and applied to the hydroelastic analysis of large floating bodies or ice sheets, characterised by variable thickness (draft), flexural rigidity and mass distributions, lying over variable bathymetry regions. A parallel-contour bathymetry is considered joining two regions of constant but possibly different depths. We treat the scattering problem of harmonic, obliquely-incident, surface waves, under the combined effects of variable bathymetry and a floating elastic plate in the variable bathymetry region. Under the assumption of small-amplitude incident waves and small plate deflections, the hydroelastic problem is formulated within the context of linearised water-wave and thin elastic-plate theory. Using domain decomposition, the problem is reformulated as a transmission one in a bounded subdomain containing the elastic body and the bottom irregularity. In order to consistently represent the wave field beneath the elastic floating plate, down to the sloping bottom boundary, a complete, local, hydroelastic-mode series expansion of the wave field is used, enhanced by an appropriate sloping-bottom mode. The latter permits the consistent satisfaction of the Neumann bottom-boundary condition on a general topography, enabling thus modelling of scattering over steep bottom topography, and extending previous approaches to the same problem invoking the mild-slope approximation (Porter&Porter 2004) or more complete modal expansions (Bennets et al 2007). Numerical results concerning floating structures of variable characteristics or ice sheets of variable thickness, lying over general shoaling seabeds, are presented and discussed. b.51 Politis, C, Ginnis, A., Kaklis, P., Belibassakis, K., Feurer, C., 2009, An isogeometric BEM for exterior potential-flow problems in the plane. SIAM - ACM Joint Conference on Geometric Design, San Francisco. In this paper, the isogeometric concept introduced by Hughes, in the context of Finite Element Method, is applied to Boundary Element Method (BEM), for solving an exterior planar Neumann problem. The developed isogeometric-BEM concept is based on NURBS, for representing the exact body geometry and employs the same basis for representing the potential and/or the density of the single layer. In order to examine the accuracy of the scheme, numerical results for the case of a circle and a free-form body are presented and compared against analytical solutions. This enables performing a numerical error analysis, verifying the superior convergence rate of the isogeometric BEM versus low-order BEM. When starting from the initial NURBS representation of the geometry and then using knot insertion for refinement of the NURBS basis, the achieved rate of convergence is O(DoF¡4). This rate may be further improved by using a degree-elevated initial NURBS representation of the geometry (kh-refinement).

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b.52 Belibassakis, K., A combined panel method / coupled-mode technique for the spatial evolution of ship-generated wave systems over variable bathymetry regions, 10th International Conference on Fast Sea Transportation, FAST 2009, Athens, Greece. In the present work, a combined panel method/coupled-mode technique is presented with application to the evolution of the ship wave system over variable bathymetry regions, characterised by parallel depth contours, without any mild-slope approximation. Under the assumption that the ship’s track is straight and parallel to the depth contours, and relatively far from the bottom irregularity, the spatial evolution of the ship wave system in a coastal environment is efficiently calculated by means of a coupled-mode model able to transform the ship’s spectrum over variable bathymetry regions. This model takes into account propagation, refraction and diffraction wave phenomena. The present method can be used, in conjunction with ship’s near-field wave data in deep water or in constant depth, as obtained by the application of ship CFD codes, or experimental measurements, to support the study of wave wash generated by fast ships and its impact on the nearshore/coastal environment b.53 Belibassakis, K., Gerostathis, Th, Politis, C., Kaklis, P., Ginnis, A., Mourkogianis, D., 2009, A novel BEM-isogeometric method with application to the wavemaking resistance problem of bodies at constant speed. Intern. Maritime Association Mediterranean Conference, IMAM 2009, Istanbul. In the present work IsoGeometric Analysis (IGA), initially proposed by Hughes et al (2005), is applied to the solution of the Boundary Integral Equation (BIE) associated with the Neumann-Kelvin (NK) problem and the calculation of the wave resistance of ships, following the formulation by Brard (1972) and Baar & Price (1988). As opposed to low-order panel methods, where the body is represented by a large number of quadrilateral panels and the velocity potential is assumed to be piecewise constant or approximated by low degree polynomials on each panel, the isogeometric concept is based on exploiting the NURBS basis of the representation the body geometry and adopts the same basis for approximating the singularity distribution or, in general, the dependent physical quantities. To this respect, the present approach, although focusing on the linear NK problem which is appropriate for thin ship hulls, it has the novelty of bringing together modern integrated CAD systems for ship-hull design with CFD solvers. In order to examine the accuracy of the present method, at a first stage, numerical results obtained in the case of a submerged prolate spheroid are compared against the analytical solution (Farell 1973) and low-order panel method predictions (Belibassakis 2004), illustrating the superior performance of the isogeometric approach. b.54 Belibassakis, K., 2009, Effects of wave-induced ship motion on propeller-hull interaction with application to fouling estimation and propulsion optimization. Internat. Maritime Association Mediterranean Conference, IMAM 2009 Istanbul. In this work we examine the effects of ship wave-induced vertical oscillatory motion on the modification of propeller’s thrust deduction and relative rotative efficiency, obtained by means of a non-linear BEM for unsteady propeller analysis (Belibassakis & Politis 1998, 2002). Results from the present analysis, in conjunction with predictions of the added resistance obtained by strip theory and the radiated energy method (see, e.g., Arribas 2007), are then used to illustrate applicability in the case of an AFRAMAX 105000tn DWT tanker, for which continuously measured data are available including ship’s load and speed, shaft RPM, thrust and torque, environmental conditions etc. The present analysis could support ship and fleet monitoring systems integrated with engine and control systems aiming to maximize operating efficiency and optimize ship’s planning of docking for hull cleaning and propeller polishing. b.55 Belibassakis, K.A., Gerostathis, Th.P., Athanassoulis, G.A., 2010, A coupled-mode model for the transformation of wave systems over inhomogeneous sea/coastal environment, 29th International Conference on Offshore Mechanics and Arctic Engineering, OMAE2010, Shanghai, China. The transformation of the directional wave spectrum over an inhomogeneous sea/coastal environment is considered. Inhomogeneities include intermediate-water depth, strongly varying 3D bottom topography and ambient currents. The consistent coupled-mode model, developed by Athanassoulis and Belibassakis (1999), extended to three dimensions by Belibassakis et al. (2001) and applied to the transformation of wave systems over 3D bottom topography (Gerostathis et al 2008) is exploited for the calculation of the transfer function, connecting the incident wave with the wave conditions at each point in the field. This model is fully dispersive and takes into account reflection, refraction, and diffraction phenomena. In the present work, the coupled mode system is enhanced to account also for

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the effects of steady currents (Belibassakis et al, 2008), as well as, the effect of wave energy dissipation due to bottom friction and wave breaking. Numerical results obtained by the present model are compared with other models (as, e.g., Li et al 1993, Yoon et al 2004) and experimental measurements (Vincent and Briggs 1989), demonstrating the usefulness and practical applicability of the present method. b.56 Belibassakis K.A. A coupled-mode model with application to the prediction of long-waves induced by short-wave groups, in general bathymetry regions, 9th HSTAM International Congress on Mechanics Limassol, Cyprus, 12 – 14 July, 2010 In the present work the coupled-mode model, developed by Athanassoulis & Belibassakis (1999) for the propagation of water waves over variable bathymetry regions, and generalized to include dissipation due to bottom friction and breaking effects, is applied to calculate the spatial evolution of short-wave groups propagating over a shoaling area, characterized by general bottom topography. The present model is appropriately modified in the surf zone in order to destroy the short-wave modulation, keeping the wave height decay in proportion to the local water-depth, and is used to calculate radiation stresses associated with shoaling of short-wave groups in the area of general bathymetry and in the surf zone. Then, the system of long-wave equations, corresponding to zero (set-down/set-up) and first harmonics, forced by the radiation stresses, is numerically solved. Except of the treatment of general bottom topography, the present approach also includes the effect of reflection/diffraction to the propagation/modulation of short-wave groups, as well as to the induced long wave motion. Results are presented showing that the present model provides reasonable predictions, supporting the study of infragravity waves induced by short-wave groups and their effects on harbors and large-vessel mooring systems operating in nearshore/coastal regions. b.57 Belibassakis, K.A., 2010, Roll response of ship-hull sections in variable bathymetry regions by a hybrid BEM - vortex particle method, 9th Intern. Conference on Hydrodynamics, ICHD 2010, Shanghai, China. A non-linear, hybrid method has been developed with application to the problem of roll response of ship-hull sections of general shape, floating in general bathymetry regions. Using domain decomposition, the present method is based on boundary element formulation for the representation of the non-linear potential wave motion around the floating body, in combination with vortex particle method for the generation of vorticity in the boundary layer and numerical simulation of vorticity convection and viscous diffusion in subregions close to the solid boundary. Subsequently, hydrodynamic forces on the floating body are obtained by pressure integration, and the hydrodynamic coefficients (added mass, damping) are calculated. Numerical results are presented and compared with experimental data and other methods. It is shown that the present method provides results of reasonable accuracy, illustrating that the mixing of boundary integral methods and particle methods is a useful tool for the evaluation of ship-hull characteristics in rolling motion, where viscous effects associated with boundary layer separation could be significant. b.58 Belibassakis, K., Gerostathis, Th, Kostas, K., Politis, C., Kaklis, P., Ginnis, A., Feurer, C., 2011, A BEM-isogeometric method with application to the wavemaking resistance problem of ships at constant speed. 30th International Conference on Offshore Mechanics and Arctic Engineering, OMAE2011, Rotterdam, The Netherlands. In the present work IsoGeometric Analysis (IGA), initially proposed by Hughes et al (2005), is applied to the solution of the boundary integral equation associated with the Neumann-Kelvin (NK) problem and the calculation of the wave resistance of ships, following the formulation by Brard (1972) and Baar & Price (1988). As opposed to low-order panel methods, where the body is represented by a large number of quadrilateral panels and the velocity potential is assumed to be piecewise constant (or approximated by low degree polynomials) on each panel, the isogeometric concept is based on exploiting the NURBS basis, which is used for representing exactly the body geometry and adopts the very same basis functions for approximating the singularity distribution (or in general the dependent physical quantities). In order to examine the accuracy of the present method, in a previous paper Belibassakis et al (2009), numerical results obtained in the case of submerged bodies are compared against analytical and benchmark solutions and low-order panel method predictions, illustrating the superior efficiency of the isogeometric approach. In the present paper we extent previous analysis to the case of wavemaking resistance problem of surface piercing bodies. The present approach, although

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focusing on the linear NK problem which is more appropriate for thin ship hulls, it carries the IGA novelty of integrating CAD systems for ship-hull design with computational hydrodynamics solvers. b.59 Belibassakis, K., 2011, Infragravity waves induced by short-wave groups in coastal regions characterized by general bottom topography, 30th International Conference on Offshore Mechanics and Arctic Engineering, OMAE2011, Rotterdam, The Netherlands. The free long-wave generation by short-wave groups over a sloping bottom is studied both experimentally and theoretically by various authors showing important results concerning the modelling of energy transfer from the short waves to subharmonics. In the present work, the coupled-mode model developed by Athanassoulis & Belibassakis (1999) for the propagation of water waves over variable bathymetry regions, as generalized to include dissipation due to bottom friction and breaking effects, is applied to calculate the spatial evolution of short-wave groups propagating over a shoaling area, characterized by general bottom topography. Following Schäffer (1993), the present model is appropriately modified in the surf zone in order to destroy the short-wave modulation, keeping the wave height decay in proportion to the local water-depth, and is then used to calculate radiation stresses associated with shoaling and breaking of short-wave groups in the area of general bathymetry and in the surf zone. Subsequently, the system of long wave equations, corresponding to zero (set-down/set-up) and first few harmonics, forced by the radiation stresses, is numerically solved. Results are presented showing that the present model provides reasonable predictions, supporting the study of infragravity waves induced by short-wave groups and their effects on harbors and mooring systems of large vessel operating in nearshore/coastal regions. b.60 Athanassoulis, G.A., Belibassakis, 2011, A fast-convergent spectral method for wave propagation and scattering in non-uniform waveguides, 7th GRACM International Congress on Computational Mechanics, Athens June 2011. We consider the problem of time-harmonic wave propagation and scattering in a non uniform waveguide governed by a general second-order, strongly elliptic equation, with variable coefficients. An improved coupled-mode method is presented, based on an enhanced local-mode series for the representation of the wave field, which includes an additional mode accounting for the effects of the boundary slope. The additional mode provides an implicit summation of the slowly convergent part of the local-mode series, rendering the remaining part to be fast convergent. Using the enhanced representation, in conjunction with an appropriate variational principle, a new system of coupled-mode equations is derived for the determination of the unknown modal-amplitude functions. Numerical applications are presented illustrating the role and significance of the additional mode and the efficiency of the present coupled-mode theory, which can be naturally extended to treat propagation and scattering problems in three-dimensional multi-layered waveguides. b.61 Belibassakis, K., 2011, A panel method based on vorticity distribution for the calculation of free surface flows around ship hull configurations with lifting bodies. Intern. Maritime Association Mediterranean Conference, IMAM 2011, Genoa, Italy. In the present paper a panel method is developed for the calculation of free surface flows around ship hull configurations including lifting bodies. The method is based on source distribution on the wetted surface of the hull and the free-surface, in conjunction with vorticity distribution of the lifting bodies and trailing vortex sheets. A free wake analysis has been applied in order to locate the position of the vortex sheets. The non-linear boundary conditions on the free surface are satisfied by iterations, starting from a linearization. Detailed numerical results are presented, including initial comparisons against other methods and measured data, illustrating the efficiency and usefulness of the present approach. b.62 Belibassakis, K., 2011, A coupled-mode model for water-wave induced groundwater pressure and flow in variable bathymetry regions and beaches. Intern. Maritime Association Mediterranean Conference, IMAM 2011, Genoa, Italy. Beach groundwater-swash interaction is a subject of interest in coastal engineering, sediment transport and groundwater circulation. Focusing on the region where water depths are greater than the wave breaking depth, a phase-resolving coupled-mode model is developed for modelling water wave

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propagation in variable bathymetry and coastal regions and its interaction with porous flow in the porous layer under the penetrable seabed of general shape, characterized by sloping parts and undulations. Theoretical analysis and experimental results in this direction have been presented by Massel (2004, 2005) who developed a closed-form solution, in constant depth, for the pore-water pressure component and velocity circulation pattern induced by surface waves. The present model is also based on Biot’s theory, taking into account volume change and pore-water flow, and extends previous work (Athanassoulis & Belibassakis 1999, Belibassakis et al 2007) to variable bottom topography in the presence of penetrable bottom, enabling prediction of wave-induced groundwater dynamic pressure and flow in the porous medium. b.63 Belibassakis K.A., Georgiou Y., Athanassoulis G.A. 2012, Interaction of Random Sea Waves with Floating Structures in General Bathymetry Regions, 22 International Offshore and Polar Engineering Conference Rhodes (ISOPE2012), Greece. The interaction of a random incident wave field with a floating structure in variable bathymetry regions is studied, considering the free surface displacement process in the context of first-order potential theory. The hybrid model developed by Belibassakis (2008) is employed to obtain the hydrodynamic analysis of the system. The above model is based on the coupled-mode theory for the propagation of water waves in general bottom topography, developed by Athanassoulis and Belibassakis (1999), in conjunction with a boundary integral equation formulation using Rankine source-sink distributions for the representation of the near field. In the simple 2D case and normally incident waves, the far-field is modelled by normal-mode series expansions derived by separation of variables in the constant-depth half-strips modelling the regions of wave incidence and transmission, respectively. Numerical results are presented demonstrating that wave-structure-bottom interactions could have a significant effect on the free surface elevation, quite similarly as in the case of wave-bottom interaction in variable bathymetry studied by Athanassoulis et al (2003). The modifications are interpreted according to a variation parameter defined as the ratio of the standard deviation of the free surface elevation in the scattered-radiated wave field over the standard deviation of the free surface of the incident wave. Generalizing the approach recently presented by Malara et al (2011), the interaction between a high wave and the floating structure is subsequently investigated, in the space domain and in the time domain, by means of the Quasi-Determinism theory (see Boccotti 2000), allowing the estimation of the free surface displacement when an extreme wave crest occurs in the vicinity of the floating structure. b.64 Belibassakis K.A., Politis, G.K., 2012, Hydrodynamic Analysis of Flapping Wing Systems for Augmenting Ship Propulsion in Rough Sea, 22 International Offshore and Polar Engineering Conference Rhodes (ISOPE2012), Greece. In the present work the analysis of an oscillating wing, located beneath the ship’s hull, in random motion, is examined as an unsteady thrust production mechanism, augmenting the overall propulsion system of the ship. The wing undergoes a combined vertical and angular oscillatory motion, while travelling at constant forward speed. The vertical motion is induced by the random motion of the ship in waves, essentially due to ship heave and pitch, while the wing pitching motion is selected as a proper function of wing vertical motion and it is imposed by an external mechanism. Numerical results are presented for the thrust produced by the biomimetic wing as well as the resulting reduction in ship motions over a range of motion parameters. Our calculations indicate that the biomimetic wing is the proper mechanism for transforming the hull kinetic energy to useful thrust, augmenting, thus, the ship propulsion in rough seas with simultaneous reduction in ship motions. The present method can serve as a useful tool for the assessment and the preliminary design and control of such thrust-augmenting devices, which enhance the overall performance of a ship in a wavy environment. b.65 Belibassakis K.A., Papathanasiou Th., Filopoulos S.P, 2012, A fast-convergent spectral method for harmonic wave propagation in inhomogeneous layered waveguides, 22 International Offshore and Polar Engineering Conference Rhodes (ISOPE2012), Greece. A fast-convergent spectral model is presented for harmonic wave propagation and scattering problems in stratified, non uniform waveguides, governed by the Helmholtz equation. The method is based on a local mode series expansion, obtained by utilizing variable cross-section eigenfunction systems defined through the solution of eigenvalue problems formulated along the waveguide, and including additional modes accounting for the effects of inhomogeneous waveguide boundaries and/or interfaces. The

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additional modes provide an implicit summation of the slowly convergent part of the local-mode series, rendering the remaining part to be fast convergent, increasing the efficiency of the method, especially in long-range propagation applications. Using the enhanced representation, in conjunction with an energy-type variational principle, a coupled-mode system of equations is derived for the determination of the unknown modal-amplitude functions. In order to treat the local vertical eigenvalue problems in the case of multilayered waveguides h- and p-Finite Element Methods have been applied exhibiting robustness and good rates of convergence. On the basis of the above, the coefficients of the coupled-mode system are calculated by numerical integration. Finally, the solution of the present coupled-mode system is obtained by using a finite difference scheme based on a uniform grid and using second-order central differences to approximate derivatives. Numerical examples are presented in simple 2D acoustic propagation problems, illustrating the role and significance of the additional mode(s) and the efficiency of the present model, that can be naturally extended to treat propagation and scattering problems in more complicated 3D waveguides. b.66 Katsardi V., Boundris G., Tsoukala VK., Belibassakis K.A., 2012, Study of wave transformation due to flushing culverts in coastal structures, 22 International Offshore and Polar Engineering Conference Rhodes (ISOPE2012), Greece. In the present paper is investigated whether certain advances in numerical methods can describe the phenomenon of wave transmission from windward to leeward of a coastal structure through flushing culverts. A series of experimental data is presented, where a 2-D physical model has been constructed which can be characterized as a typical part of a rubble mound breakwater, and compared with a non-linear coupled-mode system of horizontal equations, modeling the evolution of nonlinear water waves in finite depth over general bottom topography. Numerical results are presented for waves propagating over regions with submerged breakwaters, simulating flushing curvets that are never perfectly filled with water. The discussion focuses on the comparisons between the model and the experimental data in terms of the reflection and transmission coefficients. b.67 Belibassakis K.A., Politis, G.K., 2012, Roll stabilization by vertical thrust-producing flapping wings using active pitch control, Proceedings of the 11th International Conference on the Stability of Ships and Ocean Vehicles (STAB2012), 23-28 September 2012, Athens, Greece. The analysis of vertical oscillating wing located beneath the ship’s hull is investigated as an unsteady thrust production mechanism, augmenting the overall propulsion system of the ship. The wing undergoes a combined flapping and pitching oscillatory motion, in a uniform inflow and in the presence of waves. The flapping motion is induced by the motion of the ship in waves, essentially ship rolling and swaying. The pitching motion of the wing about its pivot axis is properly selected as a function of the ship rolling motion in order to produce thrust, with simultaneous generation of useful antirolling moment for ship stabilization. Ship flow hydrodynamics are modeled using a Rankine source-sink formulation and ship responses are calculated taking into account the additional forces and moments due to the above biomimetic propulsion system. Extending previous approach by the authors, a 3-D panel method is applied to model the unsteady lifting flow around the system. Free-wake analysis is incorporated to account for the effects of non-linear wing wake dynamics, at high translation velocities and amplitudes of the oscillatory motion. b.68 Belibassakis K.A., Athanassoulis G.A., Gerostathis Th.P. 2013, Hydroelastic analysis of Very Large Floating bodies over variable bathymetry regions , 10th HSTAM International Congress on Mechanics Chania, Crete, Greece, 25 – 27 May, 2013. The coupled-mode model developed by Belibassakis & Athanassoulis (2005) is extended and applied to the hydroelastic analysis of three-dimensional large floating bodies of shallow draft or ice sheets of small thickness, lying over variable bathymetry regions. A general bathymetry is assumed, characterised by a continuous depth function, joining two regions of constant, but possibly different, depth. Following previous works for the propagation and diffraction of water waves over three-dimensional bathymetric terrains (Belibassakis et al 2001, Gerostathis et al 2008), we consider the scattering problem of harmonic, obliquely-incident surface waves, under the combined effects of variable bathymetry and a floating elastic plate of orthogonal planform shape. Under the assumption of small-amplitude waves and small plate deflections, the hydroelastic problem is formulated within the context of linearised water-wave and thin elastic-plate theory. In order to consistently treat the wave field beneath the elastic floating plate, down to the sloping bottom boundary, a complete, local, hydroelastic-mode series expansion of the wave field is used, enhanced by an appropriate sloping-

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bottom mode. The latter enables the consistent satisfaction of the Neumann bottom-boundary condition on a general topography. Numerical results concerning floating structures lying over flat and inhomogeneous seabeds are comparatively presented, and the effects of wave direction, bottom slope and bottom corrugations on the hydroelastic response are presented and discussed. b.69 Belibassakis K.A., Athanassoulis G.A., Papathanasiou T.K. , Markolefas S.I., Kokkinos Tr., 2013, A coupled-mode system for shear deformable beams and plates of non-uniform thickness, 10th HSTAM International Congress on Mechanics Chania, Crete, Greece, 25 – 27 May, 2013. A new coupled system of horizontal equations is presented, based on the theory of shear deformable plates (or beams), derived by an enhanced representation of the elastic displacement field. The present model contains additional elastic vertical modes, permitting the shear stress to vanish on both the upper and lower boundaries of an elastic body characterized by non-uniform finite thickness. It naturally extends third-order plate theories by Reddy and Bickford (1984) to plates and beams of general shape; see also Wang & Reddy (2000). In the case of beams such a model was introduced and studied by Athanassoulis and Belibassakis (1999), in the context of hydloelastic analysis of thick floating ice-sheets. The present coupled-mode system of horizontal differential equations is obtained by means of Kantorovič’s method as applied to the variational principle for the Hamiltonian of an elastic deformable body. The proposed representation of the displacement field extends the models of Reddy and Bickford by introducing additional terms in the expansion, permitting shear stress to vanish at the sloping boundary surfaces of a plate of finite and non-uniform thickness. The extended model is presented and discussed for the case of both beams and plates. Numerical examples concerning modal analysis of beams are presented and compared against FEM solutions. Finally, the utilization of the derived model for the hydroelastic analysis of generally shaped floating bodies of very large horizontal dimensions, such as ice sheets or VLFS lying over general bathymetry regions, is discussed.

b.70 Filippas, E., Belibassakis K.A., 2013, Free surface effects on hydrodynamic analysis of flapping foil thrusterS in waves, 32th International Conference on Offshore Mechanics and Arctic Engineering (OMAE2013), June 9-14, 2013 - Nantes, France.

The analysis of an oscillating wing located beneath the ship’s hull is investigated as an unsteady thruster, augmenting the overall propulsion of the ship and offering dynamic stabilization. The unsteady thruster undergoes a combined oscillatory motion in the presence of waves. For the system in horizontal arrangement the vertical heaving motion is induced by the motion of the ship in waves, essentially ship heave and pitch, while the rotational pitching motion of the flapping propulsor about its pivot axis is set by an active control mechanism. Our method is based on coupling the seakeeping operators associated with the longitudinal and transverse ship motions with the hydrodynamic forces and moments produced by the flapping lifting surfaces, using simplified unsteady lifting line theory. First numerical results presented in Belibassakis & Politis (2012) indicate that high levels of efficiency are obtained in sea conditions of moderate and higher severity, under optimal control settings. For the detailed investigation of the effects of the free surface in the present paper a potential-based panel method has been developed for the hydrodynamic analysis of 2D hydrofoil operating beneath the free surface, undergoing heaving and pitching oscillations while moving with constant forward speed. The instantaneous angle of attack is influenced by the foil oscillatory motion and by the incident waves. At a first stage of development we consider moderate submergence and relatively low speeds permitting us to approximately neglect effects due to breaking waves and cavitation. Numerical results are presented concerning the numerical performance of the developed BEM. Also, results concerning the thrust coefficient and the efficiency of the system over a range of motion parameters, including reduced frequency, Strouhal number, and feathering parameter, are compared against other methods. Our analysis indicates that significant efficiency can be obtained under optimal operating conditions. Thus, the present method can serve as a useful tool for assessment and the preliminary design and control of such systems extracting energy from sea waves for marine propulsion. b.71 Katsardi V., Tsoukala VK., Belibassakis K.A., 2013, Estimation of Wave Transmission through Flushing Culverts in Breakwaters Study of wave transformation due to flushing culverts in coastal structures, 32th International Conference on Offshore Mechanics and Arctic Engineering (OMAE2013), June 9-14, 2013 - Nantes, France.

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In the present paper a Coupled-Mode System Model is used for the numerical simulation of wave transmission through flushing culverts. Numerical results are presented for waves propagating over regions with submerged breakwaters, simulating flushing culverts that are never perfectly filled with water. These are compared with a series of 64 experiments, for different wave conditions and/or geometrical characteristics of the openings. The present numerical approach has given good comparisons with more than the 50% of the experimental data. Deviations were observed when simulating steeper waves and/or narrower culverts, enabling the identification of the cases where the increased effects of nonlinearity, the generation of higher harmonics and 3D effects are important and should be taken into account. Nevertheless, the present model can be used as a useful starting tool in calculating efficiently the effectiveness of a flushing culvert in terms of maintaining water quality in a harbor basin. b.72 Belibassakis K.A., Politis, G.K., Gerostathis Th.P. 2013, Calculation of ship hydrodynamic propulsion in rough seas by non-linear BEM with application to reduction of energy losses in waves, 32th International Conference on Offshore Mechanics and Arctic Engineering (OMAE2013), June 9-14, 2013 - Nantes, France. Environmental conditions corresponding to realistic sea states (which can be rarely considered calm) significantly affect ship propulsion due to added wave resistance, wind resistance and other factors, as e.g., continuous rudder motion for steering in adverse conditions. In addition, external factors such as ocean currents, which determine the actual flow on the ship, critically affect the actual behavior of the propulsion system. All the above cause significant additional energy losses that sometimes could drive the propulsion system of a ship at its limits. On the other hand, the operation of ship propellers and thrusters in real sea conditions is quite different from their design specifications, usually considered in calm conditions. For example, the vertical stern motion of the ship significantly affects propeller efficiency and becomes dramatically worse if emergence of propeller occurs in high waves. Operation of the ship propulsion system in random waves causes significant variations in performance. In this work we examine in detail the effects of wave-induced motions of the ship on the modification of propulsive thrust and efficiency. Our analysis is based on the non-linear Unsteady Boundary Element Modeling Code UBEM which is applied for the analysis of an unsteadily moving propeller in a wake field, in conjunction with seakeeping analysis in regular and irregular waves. Results from the present hydrodynamic analysis, in conjunction with predictions of added resistance, are used to illustrate applicability in the case of an AFRAMAX tanker, investigating the benefits of small regulation of ship speed and engine RPM from the point of view of optimizing ship’s propulsive performance and reduction of energy losses. The present analysis could support the development of ship monitoring and decision support systems, integrated with engine control systems, aiming to maximize operating efficiency in realistic sea conditions. b.73 Katsardi V., Tsoukala VK., Belibassakis K.A., 2013, 3D Wave Transformation through Openings in Coastal Structures, 32th International Conference on Offshore Mechanics and Arctic Engineering (OMAE2013), June 9-14, 2013 - Nantes, France. Standard openings in coastal structures are the flushing culverts at breakwaters, allowing periodic exchange of the harbor basin water leading to improved water quality. These openings involve sudden water depth changes occurring when the incident waves meet these openings and transmitted into the harbour. The wave transformations during wave propagation through flushing culverts are dominated by 3D diffraction effects due to sudden water depth changes, along with the finite width of the culvert. A new coupled-mode model, based on eigenfunctions expansions of the Laplace equation, is developed and applied to the numerical solution of the local 3D wave flow problem at the opening. The harmonic wave field is excited by incident parallel waves. The numerical solution converges rapidly, permitting the series truncation at its first terms. The proposed method fully accounts for the 3D diffraction effects and produces information to couple with mild-slope models describing efficiently wave propagation and transformation in coastal regions. b.74 Belibassakis K.A., Athanassoulis G.A., Papathanasiou Th., Filopoulos S.P, 2013, A coupled mode – hp FEM for the hydroelastic analysis of shear-deformable floating bodies of general thickness in variable bathymetry Computational Methods for Coupled Problems in Science and Engineering V, 17-19 June 2013, Ibiza, Spain.

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An efficient computational procedure is presented for the solution of coupled hydroelastic problems involving bodies of general thickness, floating over variable bathymetry regions. The problem is treated by the coupled mode system of horizontal equations derived by Athanassoulis and Belibassakis (2009), for the analysis of floating, shear deformable plates or beams. The proposed plate (or beam) model is based on the addition of extra vertical elastic deformation modes, at each horizontal position along the floating body, permitting shear strain and stress to vanish on both the upper and lower boundaries and extending third-order plate theories. The final coupled mode system is derived from a variational principle combining the one – field functional of the elastodynamics in the plate region with the pressure functional in the water region. The wave potential in the water column is represented by means of a local – mode expansion that also contains an extra mode, accounting for not mildly sloped bottom variations. The addition of the additional modes results to increased convergence rate, enabling high accuracy with the use of a relatively small number of vertical modes. In the present work the hp version of the Finite Element Method is applied to the solution of the resulting system of coupled horizontal differential equations with respect to the modal amplitudes, providing good convergence rates and adaptivity capabilities, and increasing the overall efficiency of the solution strategy. Numerical results are presented demonstrating the overall robustness of the modelling and solution procedure. b.75 Belibassakis K.A., Athanassoulis, G.A., Gerostathis Th.P., Katsardi V., 2013, Transformation of wave conditions in nearshore and coastal areas by a 3D coupled-mode wave model Intern. Maritime Association Mediterranean Conference, IMAM 2013, La Coruna, Spain. The fully dispersive, coupled-mode model introduced by Athanassoulis & Belibassakis (1999), and further extended to 3D by Belibassakis et al (2001), Gerostathis et al (2008) and modified to include effects of ambient currents by Belibassakis et al (2011), is exploited in order to transform wave conditions from offshore to nearshore and coastal areas of interest, which are characterized by possibly non-mild spatial inhomogeneities. The present model takes fully into account reflection, refraction, and diffraction phenomena, due general bottom topography, permanent structures and ambient currents, and includes dissipation of wave energy due to bottom friction and wave breaking. Numerical results are presented and compared with other methods and experimental data for model validation, demonstrating also the usefulness and practical applicability of the present approach, as for example, for determining the wave conditions in nearshore and coastal areas for studying further wave-seabed-body interaction problems with large floating structures. b.76 Filippas, E., Belibassakis K.A., 2013, A boundary element method for the hydrodynamic analysis of flapping-foil thrusters operating beneath the free surface and in waves, IMAM 2013, La Coruna, Spain. Flapping foil systems located beneath the ship’s hull are investigated as unsteady thrusters, augmenting the overall propulsion of the ship by extracting energy from the waves and offering dynamic ship stabilization Belibassakis & Politis (2012a,b). The foil undergoes a combined oscillatory motion in the presence of waves. For the system in the horizontal arrangement the vertical heaving motion is induced by the motion of the ship in waves, essentially ship heave and pitch, while the rotational pitching motion of the foil about its pivot axis is set by an active control mechanism. A potential-based panel method has been developed for the hydrodynamic analysis of unsteady thrust-producing hydrofoil operating beneath the free surface while moving with constant forward speed Filippas & Belibassakis (2013). In the present paper a non-linear pressure-type Kutta condition is applied leading to better agreement with experimental results. Systematic numerical results are presented concerning the thrust coefficient and the efficiency of the system over a range of motion parameters, Strouhal number, amplitude of pitching motion and phase lag between oscillatory motions and the incident waves. Our results indicate that significant efficiency can be obtained under optimal operating conditions. Thus, the present method can serve as a useful tool for assessment and the preliminary design and control of such systems (see also De Silva & Yamaguchi 2012) extracting energy from sea waves for marine propulsion. b.77 Ginnis A.-A.I, Duvigneau R., Politis C., Kostas K., Belibassakis K., Gerostathis T., Kaklis P.D., 2013, A multi-objective optimization environment for ship-hull design based on a BEM-isogeometric solver, V International Conference on Computational Methods in Marine Engineering (MARINE 2013), Hamburg, Germany.

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We present a ship-hull optimization environment integrating modern optimization techniques, a parametric ship-hull model and a novel BEM solver for the calculation of ship wave resistance. The environment is tested for a pair of optimization scenarios (local/global) for a container ship. b.78 Papathanasiou T.K., Belibassakis K.A., 2014, Hydroelastic analysis of very large floating structures based on modal expansions and FEM, EUROPMENT 2014, Venice, Italy. Three models for the interaction of water waves with large floating elastic structures (like VLFS and ice sheets) are analyzed and compared. Very Large Floating Structures are modelled as flexible beams/plates of variable thickness. The first of the models to be discussed is based on the classical Euler-Bernoulli beam theory for thin beams. This system has already been extensively studied in Adrianov & Hermans (2004), Belibassakis & Athanassoulis (2006). The second is based on the Rayleigh beam equation and introduces the effect of rotary inertia. It is a direct generalization of the first model for thin beams. Finally, the third approach utilizes the Timoshenko approximation for thick beams and is thus capable of incorporating shear deformation as well as rotary inertia effects. Anovelty aspect of the proposed hydroelastic interaction systems is that the underlying hydrodynamic field, interacting with the floating structure, is represented through a consistent local mode expansion, leading to coupled mode systems with respect to the modal amplitudes of the wave potential and the surface elevation, Belibassakis & Athanassoulis (2005, 2006). The above representation is rapidly convergent to the solution of the full hydroelastic problem, without any additional approximation concerning mildness of bathymetry and/or shallowness of water depth. In this work, the dispersion relations of the aforementioned models are derived and their characteristics are analyzed and compared, supporting at a next stage the efficient development of FEM solvers of the coupled system. b.79 Chondros, M., Katsardi, V., Tsoukala, V.K., Belibassakis, K., 2014. Experimental verification of a new 3D numerical model involving wave transformation through flushing culverts, Proc. 3rd IAHR Europe Congress of International Association for Hydro-Environment Engineering and Research, Porto, Portugal. Numerical modeling of the local 3D wave flow problem at the openings of coastal structures,such as flushing culverts at breakwaters, that allow the periodic exchange of the harbor basin water leading to an improvement of the water quality, has not been studied adequately yet. These openings involve additionally sudden changes in water depth occurring when the incident waves meet the flushing culverts and transmitted into the harbor. A new coupledmode model, based on Eigen functions expansions of the Laplace equation, has been developed and applied to the numerical simulation of such a wave field. The behavior of the numerical solution is examined showing that it converges rapidly, permitting the truncation of the series keeping only its first terms. In order to illustrate the usefulness and applicability of the above method, a new physical model was constructed and experimental measurements were undertaken in the Laboratory of Harbor Works of NTUA. The problem involves measuring time series of surface elevation of regular incident waves to a semi-infinite breakwater that includes a flushing culvert. The wave conditions vary in frequency and amplitude and the culvert dimensions vary both in width and height. In the experimental work, the wave transformations during wave propagation through flushing culverts have shown that the phenomenon is dominated by 3D diffraction effects due to sudden changes in water depth, in conjunction with the finite width of the culvert. Comparisons with the numerical model are presented indicating its ability to simulate 3D diffraction effects, as well as wave transmission through the opening monitored in the experiments. b.80 Belibassakis K.A., Athanassoulis, G.A., 2014, A coupled-mode method for acoustic propagation and scattering in inhomogeneous waveguides, 33th International Conference on Offshore Mechanics and Arctic Engineering (OMAE2014), June 8-13, 2014, San Francisco CA. We consider the problem of acoustic propagation and scattering in inhomogeneous waveguide governed by the Helmholtz equation. We focus on an ideal, cylindrically symmetric ocean waveguide, limited above by an acoustically soft boundary modelling the free surface, and below by a hard boundary modelling the impenetrable seabed with general bottom topography. The wave field is excited by a monochromatic point source, and thus, the present solution is equivalent to the construction of the Green’s function in the inhomogeneous domain. An improved coupled-mode method is developed, based on an enhanced local-mode series for the representation of the acoustic field, which includes an additional mode accounting for the effects of the bottom slope and curvature. The additional mode

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provides an implicit summation of the slowly convergent part of the series, rendering the remaining part to converge much faster, pemitting truncation of the modal expansions keeping only a few evanescent terms. Using the enhanced representation, in conjunction with an appropriate variational principle, a system of coupled-mode equations on the horizontal plane is derived for the determination of the complex modal-amplitude functions. Numerical results are presented including comparisons with analytical solutions illustrating the role and significance of the additional mode and the efficiency of the present coupled-mode tmodel, which can be naturally extended to treat propagation and scattering problems in three-dimensional, multi-layered ocean acoustic waveguides.

b.81 Filippas, E., Belibassakis K.A., 2014, Hydrodynamic analysis of flapping-foil thruster operating in random waves, 33th International Conference on Offshore Mechanics and Arctic Engineering (OMAE2014), June 8-13, 2014, San Francisco CA. Oscillating foils located beneath the ship’s hull are investigated an unsteady thrusters, augmenting the overall propulsion of the ship in rough seas and offering dynamic roll stabilization. The foil undergoes a combined oscillatory motion in the presence of waves. For the system in the horizontal arrangement the vertical heaving motion of the hydrofoil is induced by the motion of the ship in waves, essentially ship heave and pitch, while the rotational pitching motion of the foil about its pivot axis is set by an active control mechanism. In previous works, a potential-based panel method has been developed for the detailed investigation of the effects of free surface in harmonic waves, and the results are found to be in good agreement with numerical predictions from other methods and experimental data. Also, it has been demonstrated that significant energy can be extracted from the waves. In the present work we examine further the possibility of energy extraction under random wave conditions using active pitch control. More specifically, we consider operation of the foil in head waves characterized by a given frequency spectrum, corresponding to specific sea states. The effects of the wavy free surface are taken into account through the satisfaction of the corresponding boundary conditions. Numerical results concerning thrust coefficient are shown, indicating that significant efficiency can be obtained under optimal operating conditions. Thus, the present method can serve as a useful tool for the preliminary design, assessment and optimum control of such systems extracting energy from sea waves and augmenting marine propulsion. b.82 Politis C.G., Papagiannopoulos A., Belibassakis K.A., Kaklis P.D., Kostas K.V., Ginnis A.I. Gerostathis T.P., 2014, An isogeometric BEM for exterior potential-flow problems around lifting bodies, 11th World Congress on Computational Mechanics (WCCM XI & ECCM V & ECFD VI), July 20-25, Barcelona, Spain. In this paper, the Isogeometric Analysis (IGA) concept is combined with the Boundary Element Method (BEM) for solving the exterior Neumann problem associated with the steady lifting flow around a hydrofoil. The formulation of the problem is based on a Boundary Integral Equation for the associated velocity potential combined with the null-pressure jump Kutta condition at the trailing edge. The developed Isogeometric-BEM is based on a parametric NURBS representation of the hydrofoil and employs the very same basis for representing the velocity potential. The Boundary Integral Equation is numerically solved by collocating at the Greville abscissas of the knot vector of the hydrofoil's parametric representation. Numerical error analysis of the Isogeometric-BEM using h-refinement is performed and compared with classical low-order panel methods. b.83 Filippas, E., Belibassakis K.A., 2014, Design of flapping-foil thrusters for augmenting ship propulsion in waves, Proc.2nd International Conference on Maritime Technology and Engineering (MARTECH 2014), 2014 Lisbon, Portugal. Flapping wings, located beneath or sideways the ship's hull, are investigated as unsteady thrusters, augmenting the overall propulsion in waves. The main arrangement consists of horizontal wing(s) in vertical oscillatory motion induced by ship heave and pitch, while pitching about the wing pivot axis is actively controlled. In this work we examine the possibility of energy extraction in irregular wave conditions using active pitch control. We consider operation of the foil in head waves characterized by a spectrum, corresponding to specific sea states, taking into account the coupling between the hull and the flapping foil dynamics. Numerical results concerning thrust coefficient are presented, indicating that significant thrust can be obtained under general operating conditions. The present work can be exploited to derive guidelines concerning the design and optimum control of such systems extracting

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energy from sea waves for augmenting marine propulsion in rough seas, with simultaneous reduction of ship responses. b.84 Tsarsitalidis V., Politis G.K., Belibassakis K.A., 2014, Flapping wing systems for augmenting ship propulsion in waves by employing systematic data, active control and exploiting hydroelastic effects, Proc. 9th International Conference on High-Performance Marine Vehicles (HIPER 2014), 2014, Athens, Greece. The urge for increased efficiency and also for added safety lead to serious consideration of unconventional systems. Biomimetic systems (i.e. flapping -pitching and heaving- foils), have been long studied and acknowledged as highly efficient, but disregarded as difficult to design and operate, as the number of parameters for the motion of such system is larger, compared to conventional. After the development of a systematic series (Politis & Tsarsitalidis 2014) and further enrichment with additional cases, it is possible to design prescribed motion propulsors, but also to produce an active control system (by analysing the data for system identification), for the pitching motion, so that it is capable of adapting to wave induced motions. In this paper, the concept of a system that is capable of harvesting the energy of wave induced motions and converting it directly to thrust, thus working as an energy saving system and a seakeeping device, is presented and analysed. The system may be an active Propulsor (mechanically induced heaving foil motion), or an energy saving system (heaving from the ship’s motions), while the pitching motion is determined either by a simple control method like “pitch control parameter” (Politis & Politis 2012, Belibassakis & Politis 2013), a more complex state-space controller produced by analysis of the systematic data (Belibassakis, Xiros et al 2014) or a spring loading on the pitching axis. The potential of all methods is evaluated and designs that will lead to proof of concept experiments are presented, as well as concept designs of the final system. b.85 Makropoulos, Ch, Tsoukala, V.K., Belibassakis, K., Lykou A., Chondros M., GOourgoura P., Nikolopoulos D., 2014, Managing flood risk in coastal cities through an integrated modelling framework supporting stakeholders’ involvement: The case of Rethymno, Crete, Proc. E-proceedings of the 36th IAHR World Congress 28 June – 3 July, 2015, The Hague, theNetherlands. Coastal communities are increasingly at risk from coastal hazards such as floods. Extreme hydro-meteorological events related to sea level rise, storm surges, heavy precipitation, shoreline erosion are driven by climate variability and increase the exposure of people, livelihoods, environmental services, resources and infrastructure to hazard. Flood risk management, which aims to reduce the likelihood and/or the impacts of floods, is considered inevitable. Rethymno city in Crete is one of the case study areas that PEARL project, an EU funded research project – to be completed by 2017, will develop and apply a holistic risk reduction framework that will include multi-stressor risk assessment and risk cascading while strengthening risk governance by supporting the participation of key actors. The development of a multiscale integrated modelling framework will enable the simulation of extreme event scenarios and multiple stressors covering the whole domain from the Mediterranean Sea all the way up to hydrological boundaries of Rethymo’s river basins. The integrated modelling framework, briefly outlined in this paper, will include the estimation of atmospheric variables and the use of climate change scenarios, the estimation of wave characteristic based on a four level downscaling approach, the modelling of near shore response to hurricane impacts and storms e.g. storm surges, wave propagation, sediment transport, erosion, wave diffraction and refraction, as well as catchment hydrological and urban flood modelling. The socio-economic dimension of Rethymno’s urban system as a risk evolution factor will be also investigated through the application of Agent Based Models and Cellular Automata techniques. The developed scenarios will take into account local conditions and flood problems as well as stakeholders’ perspective, needs and ambitions. Stakeholders’ involvement and their engagement with the integrated modelling framework and its outcomes will assist the development of an actionable roadmap for flood risk management for Rethymno. b.86 Tsarsitalidis V., Politis G.K., Belibassakis K.A., 2015, Active and passive pitch-controlled flapping wing propulsors; Usage of the wake structure as performance qualifier, Proceedings VI International Conference on Computational Methods in Marine Engineering (MARINE 2015) Conference, Rome Italy. Economic and ecological needs dictate for an ever growing need for increased efficiency, both in marine propulsion and energy saving systems. Biomimetic (flapping wing) systems, have already shown a serious potential as propulsors (Politis & Tsarsitalidis 2014) and an even greater as a mechanism that converts energy from ship motions to thrust (Belibassakis & Politis 2013, Politis & Politis 2014). In this paper, the problem of passively (spring loaded) or actively pitched controlled wing is formulated and

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solved using a free wake 3D Boundary Element Method [4]. For the spring loaded case, the unsteady BEM code is used to calculate the instantaneous forcing (i.e. pitching moment) entered in the nonlinear second order PDE in time, expressing equilibrium of moments including damping and inertia, around the pitch axis. Systematic simulations were conducted for a series of harmonically heaving wings of different aspect ratios, with the instantaneous pitch selected either passively via a spring-damper system or actively using a proper control algorithm. The results regarding developed mean thrust coefficient are presented in the form of systematic diagrams compatible with the design diagrams introduced in Politis & Tsarsitalidis (2014), allowing comparison of the different flapping wing propulsors. Results are also presented for the wake patterns of the different configurations, at similar propulsive conditions, revealing the connection between the propulsive effectiveness and 3D wake structure. b.87 Karperaki A., Belibassakis K.A., Markolefas, S., Papathanasiou T.K., 2015, Higher-order FEM for nonlinear hydroelastic analysis of a floating elastic strip in shallow-water conditions, PROC. International Conference on Computational Methods for Coupled Problems in Science and Engineering (COUPLED PROBLEMS 2015) 18 - 20 May 2015, Venice, Italy. The hydroelastic response of a thin, nonlinear, elastic strip floating in shalow-water environment is studied by means of a special higher order finite element. Considering non-negligible stress variation in lateral direction, the nonlinear beam model developed by Gao is used for the simulation of large flexural displacement. Full hydroelastic coupling between the floating strip and incident waves is assumed. The derived set of equations is intended to serve as a simplified model for tsunami impact on Very Large Floating Structures (VLFS) or ice floes. The proposed finite element method incorporates Hermite polynomials of fifth degree for the approximation of the beam deflection/upper surface elevation in the hydroelastic coupling region and 5-node Lagrange finite elements for the simulation of the velocity potential in the water region. The resulting second order ordinary differential equation system is converted into a first order one and integrated with respect to time with the Crank-Nicolson method. Two distinct cases of long wave forcing, namely an elevation pulse and an N-wave pulse, are considered. Comparisons against the respective results of the standard, linear Euler-Bernoulli floating beam model are performed and the effect of large displacement in the beam response is studied. b.88 Belibassakis K.A. Athanassoulis, G.A., Karperaki A., Papathanasiou T.K., Propagation of acoustic-gravity waves in inhomogeneous ocean environment based on modal expansions and hp-FEM, Proc. International Conference on Computational Methods for Coupled Problems in Science and Engineering (COUPLED PROBLEMS 2015) 18 - 20 May 2015, Venice, Italy. A coupled mode model is presented for the propagation of acoustic-gravity waves in layered ocean waveguides. The analysis extends previous work for acoustic waves in inhomogeneous environment. The coupled mode system is derived by means of a variational principle in conjunction with local mode series expansion, obtained by utilizing eigenfunction systems defined in the vertical section. These are obtained through the solution of vertical eigenvalue problems formulated along the waveguide. A crucial factor is the inclusion of additional modes accounting for the effects of spatialy varying boundaries and interfaces. This enhancement provides an implicit summation for the slowly convergent part of the local-mode series, rendering the series rapidly convergent, increasing substantialy the efficiency of the method. Particular aspects of the method include high order Lagrange Finite Element Methods for the solution of local vertical eigenvalue problems in the case of multilayered waveguides, and Gauss-type quadrature for the computation of the coupled-mode system coefficients. The above aspects make the present method quite efficient for long range propagation in extended waveguides, such as the ones found in geophysical applications, e.g. ocean basins, as only few modes are needed for the accurate representation of the wave field. b.89 Belibassakis K., Gerostathis Th., Filippas E., Touboul J., Rey V., 2015, Oscillating hydrofoils as energy devices operating in waves and currents, 11th European Wave & Tidal Energy Conference (EWTEC2015) Nantes, France. The present work focuses on the investigation of oscillating hydrofoils in the presence of waves and currents examined as new systems for extraction and exploitation of this kind of renewable energy sources. In previous works concerning the application of flapping foil thrusters operating in waves, while travelling at constant forward speed, augmenting ship propulsion in waves (Belibassakis & Politis 2013, Filippas & Belibassakis 2014]), potential based panel methods have been developed for the

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hydrodynamic analysis of flapping hydrofoils, including the effects of the free surface. Predictions are found to be in agreement with other methods and experimental data, demonstrating that significant energy can be extracted by the present system from waves. In this work we examine the possibility of energy extraction by oscillating hydrofoils in harmonic waves and currents using active pitch control. The present method takes into account the effect of the wavy free surface through the satisfaction of the corresponding boundary conditions, as well as the velocity component due to waves and currents on the formation of the incident flow. Numerical results concerning the extracted power and the operability characteristics of the system are presented, indicating that significant output can be obtained under general operating conditions. Conclusions and guidelines are provided useful for the design and optimum control of such systems operating in the nearshore region and extracting energy from waves in the presence of ambient currents. b.90 Belibassakis K., 2015, Power absorption by arrays of wave energy converters over variable bottom topography, 11th European Wave & Tidal Energy Conference (EWTEC2015) Nantes, France. Interaction of Wave Energy Converters (WEC) operating in nearshore and coastal areas, characterized by variable bottom topography, is important for the estimation of wave power absorption, determination of the operational characteristics of the system and could significantly contribute to the efficient design and layout of WEC farms. In this case wave-seabed interactions could have a significant effect, see, e.g., Charaye et al (2014). In this work, a methodology based on the coupled-mode theory developed by Athanassoulis & Belibassakis (1999) and extended by Belibassakis et al (2001) for water wave propagation over general 3D bottom topography, is developed and applied, in conjunction with Boundary Element Method for the hydrodynamic analysis of floating bodies over general bottom topography (Belibassakis 2009) and the corresponding 3D Green’s function, to treat the propagation-diffraction-radiation problems around WEC, and calculate interaction effects of floating units with variable bottom topography at the scale of the array. An important feature of the present method is that it is free of mild-slope assumptions and restrictions. Numerical results are presented and discussed concerning simple bodies (heaving vertical cylinders) illustrating the applicability of the present method. b.91 Belibassakis K., Filippas E., Touboul J., Rey V., 2015, Hydrodynamic analysis of oscillating hydrofoils in waves and currents, Proc. 16th International Maritime Association of the Mediterranean (IMAM2015), Pula Croatia. In the present work a low-order BEM is developed and applied to numerically treat flow problems around bodies and hydrofoils operating in waves and currents. For validation and optimisation of the present model, numerical results are compared against experimental data and against theoretical predictions obtained by other methods in the case of horizontal plate in waves and current. Then, the present method is used for oscillating hydrofoils and numerical results are presented illustrating the effects of important geometrical and hydrodynamic parameters. Our results support further the investigation of performance of the above systems operating in waves and currents examined as novel biomimetic marine renewable energy convertors. b.92 Belibassakis K.A., Touboul J., Rey V., 2016, On the modeling of linear waves interacting with bathymetry in the presence of vertically sheared currents , Proc. 26th Intern. Ocean & Polae Engineering Conference (ΙSOPE2016), Rhodes, Greece. Propagation of water waves in coastal zones is strongly affected by the combined influence of currents and bathymetry variations. In the case of small amplitude waves, a coupled-mode model is developed in this work for treating the wave-current-seabed interaction problem, with application to wave scattering by non-homogeneous, vertically sheared current over general bottom topography. The scattered wave potential is represented by a series of local vertical modes containing the propagating mode and all evanescent modes, plus additional terms accounting for the satisfaction of the boundary conditions on a sloping seabed. Using the above representation, in conjunction with a variational principle, a coupled system of differential equations on the horizontal plane, with respect to the modal amplitudes, is derived. In the case of no shear the above coupled-mode system reduces to the one developed by Belibassakis et al (2011) for the propagation of small-amplitude water waves over variable bathymetry regions in the presence of ambient currents. Furthermore, if only the propagating mode is maintained in the local-mode series, the present coupled mode system reduces to a form compatible to the Extended Mild-Slope equation for surface waves interacting with a linear shear

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current recently derived and studied by Touboul et al (2015). Results are obtained by using second-order finite differences to discretize the equations which are numerically solved by iterations. Various representative test cases are considered demonstrating the effect of vorticity, which is assumed to be slowly varying in the horizontal directions, in conjunction with the additional effect of depth variations.

b.93 Belibassakis K.A., Molin B., Kimmoun O., 2016, Weakly nonlinear transformation of wavegroups

over variable bathymetry, Proc. 26th Intern. Ocean & Polae Engineering Conference (ΙSOPE2016),

Rhodes, Greece.

A coupled-mode model is developed and applied to the solution of bichromatic second-order Stokes

problem, for water waves propagating over variable bathymetry regions. The bottom profile is assumed

to be general, connecting two half-strips of constant, but possibly different depths. The present

method, in conjunction with the treatment of the corresponding monochromatic problems developed

by Belibassakis & Athanassoulis (2002), complements the second-order Stokes theory in variable

bathymetry regions, without restrictions concerning the mildness of bottom slope and without the

assumption of spatial periodicity. A specific example considered in this work deals with the generation

of long-waves by short-wave groups propagating and interacting over a sloping seabed. This problem

has been extensively studied both experimentally and theoretically, showing important results

concerning the modelling of energy transfer from the short waves to subharmonics. Results are

presented showing that the present model provides reasonable predictions, supporting the study of

infragravity waves induced by short-wave groups and their effects on harbors and mooring systems of

large vessel operating in nearshore/coastal regions. b.94 Papathanasiou T.K., Karperaki A., Belibassakis K.A., 2016, An efficient coupled-mode/FEM numerical method for linear wave propagation over 3D variable bathymetry domains, Proc. 26th Intern.Ocean & Polae Engineering Conference (ΙSOPE2016), Rhodes, Greece. A robust numerical algorithm for the simulation of linear water wave propagation over uneven bottom topography is developed. The solution strategy is based on a highly efficient reduction of the 3D problem to a system of partial differential equations by means of a consistent coupled mode series expansion for water wave propagation over variable seabed. The main feature of the proposed series representation is the incorporation of special terms in the vertical expansion basis, accounting for the bottom boundary condition of the varying seabed. The formulation of the 2D system follows from the variations, with respect to the expansion coefficients (functions of the horizontal plane spatial coordinates), of a suitably chosen energy functional. The resulting model is a variable coefficient system of second order, with respect to the spatial coordinates, Partial Differential Equations (PDEs). Linear triangular finite elements are employed for the solution of this PDE system offering flexibility in the discretization of complex 2D domains. The numerical method developed has been applied to several test cases yielding accurate representations of the wave field at relatively low computational cost and small execution times. b.95 Belibassakis K.A., Xiros N., Politis, G., Filippas, E., Aktosun E., Tsarsitalidis, V., 2016, Identification of Flapper Fin Oscillations for Active Flow Control Applications in Improved Watercraft Propulsion, Proc. 26th Intern.Ocean & Polae Engineering Conference (ΙSOPE2016), Rhodes, Greece. In this study, the data analysis of an oscillating flapping wing is conducted for the development of a describing function model obtained using a Boundary Element Method (BEM) for different geometrical kinds of flapping wings. The wing experiences a combination of vertical and angular oscillatory motion, while travelling at constant forward speed. The vertical motion is induced by ship motion in waves, essentially due to ship heave and pitch, while the wing pitching motion is selected as a proper function of wing vertical motion and it is imposed by an external mechanism. The data series obtained by simulation of the unsteady lifting flow around the system was applied to develop a closed-form lumped phenomenological model for fin motion control synthesis. Using this model a state-space controller for thrust augmentation flappers will be later developed. Our study concerning post-processing data series of thrust-producing flapping foils can in effect be a useful application for feedback control law design.

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b.96 Belibassakis K., Filippas E., Gerostathis Th., 2016, Biomimetic marine energy devices in waves and sheared currents, 2nd International Conference on Renewable Energies Offshore (RENEW2016) 24 - 26 October 2016, Lisbon, Portugal. Oscillating hydrofoils in waves and currents are considered as a novel system for the exploitation of this kind of combined renewable energy sources. Special attention is paid to the case of waves and vertically sheared currents, as appearing in the case of nearshore tidal flows. The analysis is based on an appropriate mild-slope model, in conjunction with time-domain Boundary Element Methods. The methodology takes into account the velocity due to waves and currents on the formation of the incident flow, the free surface through the satisfaction of the corresponding boundary conditions and the effects of variable bathymetry and sheared currents. Results are presented concerning the harvested power, demonstrating that significant energy output can be obtained. Our method, after further enhancements and verification, it can be applied for the design and control of such systems, extracting energy from waves in the presence of ambient currents in nearshore regions. b.97 Belibassakis K., Gerostathis Th., Athanassoulis, G.A., 2016, A 3D-BEM coupled-mode method for WEC arrays in variable bathymetry, 2nd International Conference on Renewable Energies Offshore (RENEW2016) 24 - 26 October 2016, Lisbon, Portugal. The hydrodynamic interaction of Wave Energy Converters (WECs) deployed in nearshore areas, where the bottom topography presents significant variabilities, is important for the estimation of the harvested wave power and the determination of the operational characteristics of the system, and it could be of great significance for the design and optimization of WEC array layout. In this work a methodology is presented for the treatment of the propagation-diffraction-radiation of water waves around arrays of Wave Energy Converters (WEC) taking into account the interaction of the floating units with the bottom topography at the installation area. The methodology is based on the coupled-mode model developed by Belibassakis et al (2001), for the water wave field over three dimensional general bottom topography, in combination with a Boundary Element Method, Belibassakis (2008), for the treatment of the diffraction/radiation problems and the evaluation of the flow details at the local scale of the energy absorbers. An important feature of the methodology is that it is free of mild-slope assumptions and restrictions. Numerical results are presented and discussed concerning the wave filed and the power output of a single floater as well as of an array of heaving vertical cylinders. C. CONFERENCE PAPERS (reviewed on the basis of abstract) c.1 Athanassoulis, A.M. Prospathopoulos and K.A. Belibassakis, 1996, A normal-mode solution for 3D acoustic scattering from a cylindrical island, Proceedings 3rd European Conference on Underwater Acoustics, Heraklion, Greece, (24-28 June 1996). A normal-mode solution is presented for the three-dimensional (3D) problem ofacoustic scattering from non-penetrable cylindrical island in shallow water. The acou-stic field is generated by an harmonic point source, located outside the island. The ocean environment around the island is considered range independent, with arbitrary sound speed profile, and the bottom is assumed to be rigid. A new decomposition techniqueir applied to the representation of the acoustic pressure field, which improves the efficiuncy of normal-mode calculations, enabling thus the extension of the solution to higherfrequlncies. Resuits concerning the transmission loss around an acoustically soft andan acoustically hard cyliudrical island are presented for moderate frequencies (500H2and lkHz) and isovelocity ocean environment. Generalizations to more realistic oceanenvironments are discussed. c.2 Athanassoulis and K.A. Belibassakis, 1996, Three-dimensional acoustic scattering of a source-generated field from an axisymmetric obstacle of general vertical section in a waveguide, Proceedings 3rd European Conference on Underwater Acoustics, Heraklion, Greece, (24-28 June 1996). A numerical solution technique of the Helmholtz equation in a three dimensional (3D) environment, containing axisymmetric, impenetrable obstacle (island) of arbitrary vertical section is presented. The acoustic field is generated by a point-harmonic source, located somewhere outside the scatterer. The parameters characterizing the acoustic environmenet outside the scatterer are assumed range independent, and the pioblems corresponding to aNeumann or a Dirichlet boundary condition on the scatterer af,e examined. The solution technique is based on the application of Green's theorem with an appropriate Green’s function. In the case of a scatterer with a nearly cylindrical boundary, an

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approximate solution is obtained by expanding the Green's function into a normal-mode series and applying a Galerkin’s method in order to determine the coefficients of the expansion. Numericat results are presented for the case of a conical island at low frequencies. c.3 The ‘Amfitriti’ group, National Technical University of Athens, 1996, The integrated software AMFITRITI and its application to the calculation of Transmission Losses in the Aegean Sea environment, Proceedings of the Intern. Conference Circuits, Systems and Computers 96, Piraeus, Greece, July 1996. The ‘Amfitriti’ integrated software is developed in the framework of ‘Amfitriti’ project, which is funded by the Hellenic Navy General Staff, and is carried out at the Laboratory of Ship and Marine Hydrodynamics of the National Technical University of Athens. The purpose of the ‘Amfitriti’ project is the systematical study of the hydroacoustic characteristics of the Aegean Sea. In particular, one of the principal goals of the project is the development of an integrated, user-friendly software, enabling by means of a graphical user interface system the retrieval, management and updating of environmental (geographical, oceanographic, hydroacoustic and geoacoustic) data, the execution of computations by means of available and well-established numerical codes, and the visualization of the results concerning propagation losses in underwater sound transmissions. In the present work a brief description of the main characteristics of the hydroacoustic codes for TL-calculations, which are incorporated in the integrated ‘Amfitriti’ software, is given, and selected examples from its application to typical environments from the Aegean Sea are presented. c.4 Belibassakis, K.A., Prospathopoulos, I.M., Voutsinas, S.G., Numerical modelling of noise propagation in the atmospheric environment and application to wind energy installation, Proceedings of European Wind Energy Conference, EWEC’97, Ireland October 1997. The modelling of noise propagation in the atmosphere using a combination of two well-known methodologies is examjned. The developed computational model uses a normal modes methodology for the Iow frequencypart and a raytheory methodology for the high frequency part. The capabilities and shortcomings of the model are discussed andindicative results are presented. The perspective is the application of this model to the propagation of the noiseemitted from wind turbines or parks.

c.5 Athanassoulis, G.A., Belibassakis, K.A., Development and study of the Green’s function for water

waves over variable bathymetry domains, Intern. Symposium WAVES’98, Ocean Wave Kinematics,

Dynamics and Loads on Structures, American Society of Civil Engineers, Houston Texas, April 1998.

An enhanced local-mode representation of the wave potential in variable bathymetry regions is applied

to the problem of propagation of water waves, emitted from a monochromatic point source. The

representation includes, except of the propagating mode and the infinite system of evanescent modes,

also an additional mode, which takes into account the effects of the bottom slope. Using this

representation in conjunction with a variational principle, a forced system of horizontal coupled-mode

equations is derived for the determination of the complex modal-amplitude functions. This system

contains an additional equation associated with the sloping-bottom mode and produces solutions

consistent with the bottom boundary condition. The present method provides the means for the

efficient treatment of complex wave-body interaction problems, in the case when the structures are

large and thus the local bathymetry variation effects are important. c.6 Athanassoulis, G.A., Belibassakis, K.A., Livaditi, E.L., An enhanced coupled-mode theory for sound propagation over an arbitrary bottom topography, 4th European Conference on Underwater Acoustics ECUA’98, Rome, Italy, September 1998. In the present work, the consistent coupled-mode theory derived by Athanassoulis et al (1998) is generalized in (2+1) dimensions and applied to the diffraction problem of acoustic waves from localized 3D scatterers superimposed over a parallel-contour bathymetry. The total acoustic field is decomposed into an incident field carrying out the effects of the parallel-contour bathymetry, and an associated diffraction field with forcing restricted only on the surface of the localized scatterer(s). The

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wave parameters in the horizontal (propagation) space are different at infinity in different directions, rendering the estimation of the diffraction far-field pattern a part of the problem. The vertical distribution of the diffraction potential is represented by a uniformly convergent series of local vertical modes. This series consists of the vertical eigenfunctions associated with the propagating and all evanescent modes, plus an additional mode, accounting for the bottom boundary condition when the bottom slope is not negligible. By applying an appropriate variational principle, the diffraction problem is reduced to a system of horizontal differential equations in the propagation space (the diffraction system). No simplifying assumptions concerning the bottom slope and curvature are made, and thus, the diffraction system is equivalent to the 3D boundary-value problem for the diffraction potential. To restrict the support of the diffraction system, the perfectly matched layer (PML) technique, introduced by Berenger (1994) for the absorption of electromagnetic waves, and formulated for the Helmholtz equation by Turkel & Yefet (1998) and by Collino & Monk (1998), is optimized by direct minimization of the reflection coefficient and then applied as the closure condition of the diffraction system at a finite distance from the localized scatterer. Results are presented concerning the optimum choice of the discrete PML coefficients for various values of the physical and numerical parameters, useful for the discretization of the diffraction system by a second-order finite difference scheme. The present coupled-mode theory can provide an improved rate of convergence of the modal series ensuring the uniform convergence of the 3D acoustic field up to and including the boundaries. c.7 Prospathopoulos, I.M., Belibassakis, K.A., Voutsinas, S.G., 1999, Numerical modelling of propagation of noise emitted from wind parks, Proceedings of European Wind Energy Conference, EWEC 99, Nice, France March 1999. A numerical model for the propagation of noise emissions from wind parks is described and evaluated in several cases. The model combines the well-known normal modes and ray theory methodologies. It takes into account most of the mechanisms that affect sound propagation: atmospheric absorption, ground impedance, wind velocity and terrain orography. Predictions are found in good agreement with measurements in flat terrain and are acceptable in compiex terrain. Conclusions about the behaviour of the model are deduced and further developments for improvement are suggested. c.8 Athanassoulis, G.A., Belibassakis, K.A., Gerostathis, Th., 2000, A coupled-mode theory for the scattering of acoustic waves from localized 3D scatterers superimposed over a parallel contour bathymetry , 5th European Conference on Underwater Acoustics, Lyon 2000. The consistent coupled-mode theory derived by Athanassoulis et al (1998) is generalized in (2+1) dimensions and applied to the scattering problem of acoustic waves from localized 3D scatterer(s) superimposed over a parallel-contour bathymetry. The total acoustic field is decomposed into an incident field carrying out the effects of the parallel-contour bathymetry, and an associated scattering field with forcing restricted only on the surface of the localized scatterer(s). The wave parameters in the horizontal space are different at infinity in different directions, rendering the estimation of the far-field a part of the problem. In the representation of the vertical distribution of the acoustic pressure an additional mode is introduced accounting for the bottom boundary condition when the bottom slope is not negligible. To restrict the support of the scattering problem, the Perfectly MatchedLayer technique is used as the closure condition of the scattering problem. c.9 Athanassoulis, G.A., Belibassakis, K.A., 2000, Nonlinear water wave problems over a general bathymetry: A unified theory, Proceedings of “Rogue Waves 2000”, organised by IFREMER, Brest, France Under the assumptions of incompressibility and irrotationality, the problem of evolution of water waves over a variable bathymetry region admits of at least two different variational formulations. A Hamiltonian one, proposed by Petrov (1964) and exploited further by Zakharov (1968), and an unconstrained one, proposed by Luke (1967). The present development is based on Luke's variational principle, in which the admissible fields are free of essential conditions, except for smoothness and completeness prerequisites. A complete local-mode series expansion of the wave potential is constructed, which represents exactly the vertical structure of the wave field. This series contains the usual propagating and evanescent modes, plus two additional modes, called the free-surface modeand the sloping-bottom mode, introduced in order to consistently treat the non-vertical end-conditions at the free-surface and the bottom boundaries, respectively. Using this expansion, in conjunction with

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the variational principle, the original problem is reformulated as an infinite, coupled-mode, non-linear system of second-order differential equations in the propagation (horizontal) space, fully accounting for the effects of non-linearity and dispersion. The main features of this approach are the following: (i) Various standard models of water-wave propagation are recovered by appropriate simplifications of the coupled-mode system. Among them are included the mild-slope equation(s), the second-order Stokes solutions, and the Boussinesq equation. (ii) In all cases examined, a small number of modes (up to 5 or 7) are enough for the precise numerical solution, provided that the two new modes (the free-surface and the sloping-bottom ones) are included in the local-mode series. c.10 Athanassoulis, G.A., Belibassakis, K.A., 2001, Nonlinear water wave problems over a general bathymetry: A unified variational approach, Proceedings of the Intern. Conference Progress in Nonlinear Science, Nizhny Novgorod, Russia. In the present work we consider the problemof non-linear gravity waves propagating over a general bathymetry. A complete local-mode series expansion of the wave potential has been developed and used, in conjunction with Luke's variational principle, to reformulate the original problemas an infinite, coupled- mode systemof equations in the propagation (horizontal) space. The present local-mode expansion represents exactly the vertical structure of the wave field. The series contains the usual propagating and evanescent modes, modelling the internal kinematics, plus two additional modes, the free-surface modeand the sloping-bottom mode, introduced in order to consistently treat the non-vertical end-conditions at the free-surface and the bottom boundaries, which model the boundary kinematics. The resulting coupled-mode system fully accounts for the effects of non-linearity and dispersion, in interm ediate and shallow water depth. c.11 Athanassoulis, G.A., Belibassakis, K.A., Kanellopoulos, J., 2002, A coupled-mode model for the solution to the time-harmonic Maxwell's equations in a curved waveguide of rectangular cross section, 2nd European Symposium Numerical Methods in Electromagnetics, JEE’2002, Toulouse 2002. A semi-analytical, coupled-mode technique is developed and applied to the solution of the time-harmonic Maxwell's equations and the determination of electromagnetic wave field in a curved waveguide of rectangular cross section, used as the junction of two straight waveguides. It is assumed that one dimension of the cross section of the waveguide remains constant all along the curved part. This permits us to introduce partial separation of variables, and reformulate the problem in two dimensions. The Maxwell's equations are used in tensor form, in orthogonal curvilinear coordinates, in conjunction with a local-mode series representation of the electric field. The local modes are defined, at each position along the bent waveguide, by formulating and solving local, regular Sturm-Liouville problems. Exploiting the orthogonality properties of the local modes, a coupled-mode system of differential equations with respect to the modal amplitudes is derived by a Galerkin approach. The coupled-mode system is considered in conjunction with appropriate end-conditions, ensuring the matching at the input and output ends of the bent waveguide with the incident and the transmitted fields. c.12 Athanassoulis, G.A., Belibassakis, K.A., 2002, A consistent coupled-mode theory for underwater sound propagation in a general, stratified acoustic environment, 6th European Conference on Underwater Acoustics, Gdansk 2002. The underwater acoustic b.v.p. in a sea environment characterised by general stratification and an arbitrary sea-bottom topography is reformulated as a transmission problem by decomposing the domain into three subdomains: the range-independent "near" and "far" parts, and the rangedependent (intermediate) part containing the medium and bottom irregularity. The pressure field in the range-independent subdomains, is expressed in terms of standard normal-mode series expansion. In the intermediate subdomain, a variational principle is applied to the transmission problem, in conjunction with an enhanced local-mode representation of the acoustic-pressure field, resulting in a consistent coupled-mode system of equations. This system contains additional equations, associated with the additional sloping-interface modes, and produces solutions consistent with the interface conditions and the conservation of energy. Numerical results are presented in comparison with general FEM solvers demonstrating the efficiency of the present method. c.13 Athanassoulis, G.A., Belibassakis, K.A., Dougalis, V. A., Kampanis N.A and D. A. Mitsoudis, 2002, Simulation of underwater sound propagation in a general stratified environment by a coupled mode and

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a finite element method, Forum Acusticum, 3rd European Congress on Acoustics, European Acoustics Association, Sevilla 2002. A coupled mode and a finite element method are used in numerical simulations of underwater sound propagation in axially symmetric, multilayered environments with penetrable bottom and a number of fluid layers of different acoustic properties, separated by interfaces of general topography. The schemes are compared and applied to test problems with sea-mount type interfaces, and to sloping interface environments. c.14 Athanassoulis, G.A., Belibassakis, K.A., 2002, A coupled-mode theory for underwater sound propagation in a stratified environment. Comparison of results and validation vs. a finite element method, ACOUSTICS 2002, Hellenic Institute of Acoustics, Patras University, September 2002. We consider underwater acoustic wave propagation and scattering in an axially symmetric cylindrical waveguide, consisting of several fluid layers of variable thickness overlying an impenetrable bottom. The problem is reformulated as a transmission problem by decomposing the domain into three subdomains: the range independent "near" and "far" parts, and the range-dependent (intermediate) part containing the medium and bottom irregularity. The pressure field in the rangeindependent subdomain, is expressed in terms of standard normal-mode series expansions. In the intermediate subdomain a variational principle is applied to the transmission problem, in conjunction with an enhanced local-mode representation of the acoustic- pressure field, resulting in a consistent coupled-mode system of equations. This system contains additional equations, associated with the additional sloping-interface modes, and produces solutions consistent with the interface conditions and the conservation of energy. Numerical results are presented in comparison with general FEM solvers demonstrating the efficiency of the present method. c.15 Barstow S, Mørk G, Lasse Lønseth, Peter Schjølberg, Gerassimos Athanassoulis, Kostas Belibassakis, Theodore Gerostathis and Gerard Spaan, 2003, WORLDWAVES: High quality coastal and offshore wave data within minutes for any global site, COPEDEC VΙ, 2003 Colombo, Sri Lanka, September 2003. Increased utilisation of the coastal zone to a multitude of activities including various shoreline developments related to transportation, tourism, fish farming and increasingly the wind and wave energy industries has lead to a growing demand for reliable information on the wave conditions. Reliable data are also needed with respect to the management and protection of these often fragile environments. Many of those concerned with these wave-impacted environments still use antiquated data sources, usually from offshore waters as, in the absence of long term wave data collected at the site of interest, the calculation of reliable wave statistics at a coastal site is a complicated, time consuming and expensive business, requiring various data sets to be assembled. WorldWaves simplifies and speeds up the accurate modelling of wave conditions in coastal waters by integrating the following under a single Matlab toolbox: High quality long-term wave data offshore all global coasts; Worldwide bathymetric and coastline data; SWAN and backward raytracing wave models; Sophisticated offshore and nearshore wave statistics toolboxes with tabular and graphical presentations, A facility to export ASCII time series data at offshore or inshore locations; A geographic module with easy zooming to any area worldwide; Tools to set up model grids and display and edit bathymetry and coastline; A facility for the import of user offshore data. In this paper we describe the design and implementation of WorldWaves including the fusion of satellite, model and buoy wave and wind data in the global offshore database, and apply the package to hypothetical case studies in Sri Lanka. c.16 Steve Barstow, Gunnar Mørk, Lasse Lønseth, Peter Schjølberg, Ulla B. Machado, Gerassimos Athanassoulis, Kostas Belibassakis, Theodore Gerostathis and Gerard Spaan, 2003, WORLDWAVES: High quality coastal and offshore wave data within minutes for any global site, Coasts and Ports 2003, Auckland, New Zealand. The demand for reliable information on wave conditions, in particular at coastal sites, is increasing as a result of the increased utilisation of the coastal zone to a multitude of activities (e.g. shoreline developments related to transportation, oil and gas industries, wave energy industries, etc). Reliable data is also needed with respect to the management and protection of these, often fragile, environments. Many of those concerned with these wave-impacted environments still use antiquated data sources, usually from offshore waters as, in the absence of long term wave data collected at the

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site of interest, the calculation of reliable wave statistics at a coastal site is a complicated, time consuming and expensive business, requiring various data sets to be assembled. WorldWaves considerably simplifies the modelling of wave conditions in coastal waters, resulting in more timely data, at a lower cost and at the same time retaining a high reliability. In this paper, we describe the development of WorldWaves. The offshore wave database is described in some detail, including the validation of the long-term model data against satellite and buoy data around the world. The software is illustrated by a case study in the northern area of New Zealand. c.17 Athanassoulis, G.A., Belibassakis, K.A., Gerostathis, Th., 2006, Long-term wind and wave data for Port & Harbour Engineering: Exploiting existing offshore data and numerical models to get a timely, site-specific nearshore analysis, 5th Hellenic Conference of Port Engineering, Athens November 2006 (in Greek). For the efficient design of ports and harbours, reliable information concerning the wind and wave conditions in nearshore areas and coastal sites are needed. In the absence of long term wave data collected at the site of interest, the engineers still use nearby offshore data. The calculation of reliable wave statistics at a coastal site requires various data sets to be assembled, including temporal long term representative directional wave data offshore of the site, in addition to bathymetric and coastline data. Further, a suitable wave model, capable of modelling the transfer of the offshore conditions to the site of interest, is required, incorporating the relevant shallow water wave phenomena. In the present paper, an integrated software package is presented that simplifies and speeds up the modelling of wave conditions in coastal waters, enabling us to perform a timely, site-specific nearshore analysis everywhere. This package consists of high quality long-term wave data offshore all global coasts; worldwide bathymetric and coastline data; SWAN and backward raytracing wave models; sophisticated offshore and nearshore wave statistics toolboxes with tabular and graphical presentations, including facilities to export time series data at offshore or inshore locations; a geographic module with easy zooming to any area worldwide; tools to set up model grids and display and edit bathymetry and coastline; a facility for the import of user offshore data and export of inshore time series data. c.18 Belibassakis, K.A., Gerostathis, T., Athanassoulis, G.A., 2008, Wave-current-seabed interaction over general bottom topography, Coastal Technology Workshop, COAST2008, 29-30 May 2008, Trondheim Norway. A new coupled-mode model is presented for wave-current-seabed interaction, with application to wave scattering by steady currents over general bottom topography. The vertical structure of the scattering wave potential is represented by a series of local vertical modes containing the propagating mode and all evanescent modes, plus an additional term accounting for the bottom boundary condition when the bottom slope is not negligible. Using the above representation, in conjunction with Luke’s (1967) variational principle, the wave-current-seabed interaction problem is reduced to a coupled system of differential equations on the horizontal plane. If only the propagating mode is retained in the vertical expansion of the wave potential, and after simplifications, the present system is reduced to an one-equation model compatible with Kirby’s (1984) mild-slope model (see also Liu 1990) with application to the problem of wave-current interaction over slowly varying topography. c.19 Athanassoulis, G.A., Belibassakis, K.A., Gerostathis, T., 2013, Offshore to nearshore wave spectrum transformation, taking into account wave – current – seabed interaction. 2012 Intern. Conference on Advances in Coupled Systems Mechanics (ACEM'12), Seoul, Korea. Coastal morphodynamics requires detailed information about inshore wave conditions. Since information concerning sea states is practically available offshore (e.g., from satellites or from global forecasting models), there is a strong need for developing appropriate models transforming the offshore wave conditions to nearshore ones. In the present work, the fully dispersive, consistent coupled-mode model introduced in Athanassoulis & Belibassakis (1999), and further developed in Belibassakis et al (2001), Gerostathis et al (2008) and Belibassakis et al (2011), is exploited in order to implement an offshore to nearshore wave spectrum transformation. This is achieved by defining and calculating a distributed transfer function, connecting incident wave components with the wave conditions at each point in the nearshore field. The model takes full account of reflection, refraction, and diffraction phenomena, due to strongly varying, 3D bottom topography and ambient currents, as

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well as dissipation of wave energy due to bottom friction and wave breaking. Numerical results are presented and compared with other methods and experimental data demonstrating the usefulness and practical applicability of the present approach. c.20 Belibassakis K., Filippas E., 2014, Biomimetic flapping foil thrusters for augmenting ship propulsion in waves, Proceedings Hellenic Institute of Marine Technology. Biomimetic propulsors is the subject of intensive investigation, since they are ideally suited for converting environmental (atmospheric or sea wave) energy to useful thrust, succeeding efficiencies over 100%. Recent research and development results concerning biomimetic foils and wings, supported also by extensive experimental evidence and theoretical analysis, have shown that such systems, operating under conditions of optimal wake formation, could achieve such high levels of propulsive efficiency. On the other hand, the complexity of kinematics of flapping wings necessitates the development of more sophisticated power transmission mechanisms and control devices, as compared to the standard marine propeller systems, preventing at present its application as the main or sole propulsion system of ships. In this work we present results from recent research concerning innovative biomimetic-wing system for augmenting ship propulsion efficiency, in operating conditions corresponding to realistic sea states. For the system in the horizontal arrangement, the vertical heaving motion of the hydrofoil is induced by the motion of the ship in waves, essentially ship’s heave and pitch, while the rotational pitching motion of the foil about its pivot axis is set by an active control mechanism. The latter augments the overall propulsive efficiency of the ship by extracting energy from the waves, damping at the same time partially the vertical ship motion, and offering enhanced dynamic stability. After theoretical model development combined with experimental study and validation, the examined system could contribute to greening of sea transport and safer operation of ships. c.21 Karperaki A., Belibassakis K.A., Papathanasiou T.K., 2015, Propagation of acoustic-gravit wavs in inhomogeneous ocean environment generated by sea-bottom deformation, Proc. 8th GRACM International Congress on Computational Mechanics GRACM 2015 Volos, 12 July – 15 July 2015, Greece. A coupled-mode system for the propagation of acoustic-gravity waves in inhomogeneous ocean basins is presented. The applications of such simulation include the prediction of acoustic-gravity waves, generated by extended, seismic induced dislocations/landslides, associated with tsunamis. Assuming a certain degree of ocean compressibility, the water wave model equations are enhanced in order to predict the propagation of acoustic gravity pulses that accompany tsunami generation. These disturbances travel at a much greater speed than the free-surface modes and may be employed as early warning signals. The present work extends closed form solutions, presented for homogeneous, flat bottom environments, subjected to localized seabed dislocation, into a multi-layered ocean configuration. In pursue of more realistic models, the proposed system of equations incorporates variable bathymetry and interfaces, and accounts for diffraction and shoaling effects along with refraction index variability. The derivation of the coupled mode system of equations is based on the construction of local vertical bases along the horizontal domain and the representation of the solution as an enhanced local mode expansion. The series include additional terms for the consistent treatment of variable interfaces. The extra modes result in convergence acceleration for the modal series, making the method robust and easily extendable to 3-D environments. c.22 Belibassakis K.A., 2015, Marine propulsion in waves by flapping foil systems, Proc. 8th GRACM International Congress on Computational Mechanics GRACM 2015 Volos, 12 July – 15 July 2015, Greece. Flapping foils located beneath the hull of the ship are investigated as unsteady thrusters, augmenting ship propulsion in rough seas and offering dynamic stabilization. The foil undergoes a combined oscillatory motion in the presence of waves. For the system in the horizontal arrangement, the vertical heaving motion of the hydrofoil is induced by the motion of the ship in waves, essentially ship’s heave and pitch, while the rotational pitching motion of the foil about its pivot axis is set by an active control mechanism. For the detailed investigation of the effects of the free surface and waves potential-based panel methods have been developed, and the results are found to be in good agreement with numerical predictions from other methods and experimental data. Also, it has been demonstrated that significant energy can be extracted from the waves for propulsion.

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c.23 Belibassakis K., Filippas E., Gerostathis Th., 2016, Biomimetic Systems Operating as Marine Energy Devices in Waves and Sheared Currents, 11th HSTAM Intern. Congress on Mechanics, 27-30 May 2016, Athens. The present work is focused on the investigation of oscillating hydrofoils in the presence of waves and currents studied as new systems for the exploitation of this kind of combined renewable marine energy sources. We examine the possibility of energy extraction by oscillating hydrofoils operating as biomimetic systems in harmonic waves and currents in coastal regions using active pitch control. Except currents of uniform structure in depth, special attention is paid to the case of waves and vertically sheared currents. The present method takes into account the effect of the wavy free surface through the satisfaction of the corresponding boundary conditions, the velocity component due to waves and currents on the formation of the incident flow, as well as the effects of variable bathymetry and sheared currents. Numerical results concerning the extracted power and the operability characteristics of the system over variable bathymetry are presented, indicating that significant output can be obtained under general operating conditions. Our method after further enhancements and verification can be applied for the design and optimum control of such biomimetic systems operating in the nearshore/coastal region and extracting energy from waves in the presence of ambient currents. c.24 Belibassakis K., Gerostathis Th., Athanassoulis, G.A., 2016, Performance of Arrays of Wave Energy Converters Operating in Variable Bathymetry Regions, 11th HSTAM Intern. Congress on Mechanics, 27-30 May 2016, Athens. Focusing on the case of Wave Energy Converters of essentially cylindrical shape (point absorbers), in this work, a methodology is presented to treat the propagation-diffraction-radiation problem around a number of WECs, supporting the calculation of interaction effects of floating units with variable bottom topography at the scale of the array. The present method is based on the coupled-mode model developed by Athanassoulis & Belibassakis (1999), and extended to 3D by Belibassakis et al (2001), for the water wave propagation over general bottom topography, in conjunction with Boundary Element Method for the treatment of the diffraction/radiation problems providing the hydrodynamic analysis and interaction of floating bodies over general bottom topography. An important feature of the present method is that it is free of mild-slope assumptions and restrictions. Numerical results are presented and discussed concerning isolated floaters and array of simple heaving vertical cylinders illustrating the applicability of the method. c.25 Karperaki A., Papathanasiou T.K., Belibassakis K.A., 2016, A Coupled-Mode System for the Near-Trapping of Water Waves in the Presence of Variable Bathymetry, 11th HSTAM Intern. Congress on Mechanics, 27-30 May 2016, Athens. In the linear water wave theory, trapped modes are excited at certain frequencies in the presence of fixed bodies, other obstacles or specific bathymetry variations. This resonant phenomenon represents a local, perpetual oscillation for the inviscid fluid. In this work, the near-trapping of linear waves, caused by the interaction with a seabed featuring abrupt bathymetric variations, is investigated in the time domain by means of a consistent coupled-mode theory and discretized by higher-order FEM. The proposed scheme has been found to be very efficient as it combines a rapidly convergent series representation for the wave potential, high order finite element ansatz and the capability of h-refinement. The proposed numerical scheme has been found to be robust and applied to several, computationally demanding problems, featuring near-trapping phenomena. c.26 Lampropoulos N., Koubogiannis, D., Belibassakis K., 2016, Numerical Simulation of Flapping Foil Propulsion, 11th HSTAM Intern. Congress on Mechanics, 27-30 May 2016, Athens. Flapping foil propulsion is numerically investigated by means of CFD solver. A methodology using open source CFD software (OpenFOAM) is developed and described in detail. The method is validated in the case of a harmonically flapping foil (for which experimental results are available in the literature), that oscillates at a frequency under the combined effect of a heave (vertical displacement) and a pitch motion (rotation around its axis). The influences of Strouhal number and maximum angle of attack are investigated and the production of high thrust together with high efficiency is demonstrated for a fixed Reynolds number. Numerical results are presented and compared to experimental data and the simulation method is assessed. Future work concerns similar parametric studies for various Reynolds numbers, amplitudes and frequencies of the heave and pitch motions. The aim in the long-term is to

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develop a control methodology in conjunction with the present simulation method and study the problem of seeking the optimum foil motion parameters for maximum propulsion during ship motion in sea.