Embed Size (px)
Citation preview
Innovative CFD Innovative CFD tools for tools for
hydrodynamic hydrodynamic design of IACC design of IACC
boatsboatsJ. García-Espinosa, COMPASS IS, J. García-Espinosa, COMPASS IS,
[email protected]@compassis.com
A. Souto, ETSIN, [email protected]. Souto, ETSIN, [email protected]
CFDCFDComputational Fluid Computational Fluid
DynamicsDynamics►Techniques to solve problems in Techniques to solve problems in
fluid mechanics on computersfluid mechanics on computers►Algorithms to simulate real Algorithms to simulate real
behavior of fluidsbehavior of fluids►Tools used to predict/understand Tools used to predict/understand
real behavior of a system in a fluid real behavior of a system in a fluid flowflow
Numerical Simulation Numerical Simulation Model TestingModel Testing
Numerical Numerical simulation simulation + Validation + Validation
Model testingModel testing + Extrapolation + Extrapolation
(Available) CFD Applications(Available) CFD Applications
Hull and appendages hydrodynamic resistance Hull and appendages hydrodynamic resistance calculation / Wave pattern analysiscalculation / Wave pattern analysis
Lift forces calculationLift forces calculation 2D profiles optimisation2D profiles optimisation Local phenomena analysisLocal phenomena analysis Sails simulationSails simulation Mast profile optimisationMast profile optimisation Aerodynamic resistanceAerodynamic resistance Seakeeping analysisSeakeeping analysis Other (dynamic loads estimation, velocity Other (dynamic loads estimation, velocity
prediction, ...)prediction, ...)
(Current) CFD Applications(Current) CFD Applications Hull and appendages hydrodynamic resistance calculation / Wave pattern analysis. Hull and appendages hydrodynamic resistance calculation / Wave pattern analysis.
Widely used: Linear/Nonlinear FS potential flow solverWidely used: Linear/Nonlinear FS potential flow solver Frequently used: Fully nonlinear FS RANSE solverFrequently used: Fully nonlinear FS RANSE solver
Lift forces calculationLift forces calculation Widely used: Linear/Nonlinear FS potential flow solverWidely used: Linear/Nonlinear FS potential flow solver Frequently used: Fully nonlinear FS RANSE solverFrequently used: Fully nonlinear FS RANSE solver
2D profiles optimisation2D profiles optimisation Widely used: RANSE solverWidely used: RANSE solver
Local phenomena analysisLocal phenomena analysis Widely used: Reynolds-averaged Navier Stokes (RANSE) solver.Widely used: Reynolds-averaged Navier Stokes (RANSE) solver. Comming: LES turbulence models, direct simulationsComming: LES turbulence models, direct simulations
Sails simulationSails simulation Widely used: Potential flow solver coupled to boundary layer solverWidely used: Potential flow solver coupled to boundary layer solver Coming: ALE RANSE solversComing: ALE RANSE solvers
Mast profile optimisationMast profile optimisation Widely used: RANSE solverWidely used: RANSE solver
Aerodynamic resistanceAerodynamic resistance Widely used: RANSE solverWidely used: RANSE solver
Seakeeping analysisSeakeeping analysis Widely used: Linear (frequency domain) solvers.Widely used: Linear (frequency domain) solvers. Comming: Non linear FS (time domain) solvers.Comming: Non linear FS (time domain) solvers.
Other (dynamic loads estimation, velocity prediction, ...)Other (dynamic loads estimation, velocity prediction, ...) Frequently used: RANSE VOF – Level Set methodsFrequently used: RANSE VOF – Level Set methods Comming: Lagrangean - Meshless methods Comming: Lagrangean - Meshless methods
Tdyn: Main CharacteristicsTdyn: Main Characteristics► Tdyn includes a fully integrated Tdyn includes a fully integrated
pre/postprocessor based on GiD system, pre/postprocessor based on GiD system, incorporating advanced CAD tools (NURBS incorporating advanced CAD tools (NURBS importation, creation and edition)importation, creation and edition)
► Data insertion (control volume Data insertion (control volume generation, physical properties, boundary generation, physical properties, boundary conditions, etc) is guided by the use of conditions, etc) is guided by the use of specific wizard tools for naval specific wizard tools for naval applicationsapplications
► Mesh can be automatically generated Mesh can be automatically generated from the CAD information within the from the CAD information within the system. It also allows elements size system. It also allows elements size assignment and quality check of the assignment and quality check of the resulting meshresulting mesh
► System also includes a great variety of System also includes a great variety of postprocessing options and tools for fast postprocessing options and tools for fast report generationreport generation
► System includes a tool (procserver) which System includes a tool (procserver) which allows to perform Grid-Computing allows to perform Grid-Computing calculationscalculations
► The same environment includes tools for The same environment includes tools for performing a variety of analysis performing a variety of analysis (structural, heat transfer, transport of (structural, heat transfer, transport of species, user defined problems, …) species, user defined problems, …)
TdynTdynFEM Fluid DynamicsFEM Fluid Dynamics
RANSE-NAVAL RANSE-NAVAL modulemodule
RANSE solver. RANSE solver. Characteristics.Characteristics.
Implicit and accurate scheme: In most of the cases of interest for the Implicit and accurate scheme: In most of the cases of interest for the naval architecture the time step imposed by the stability criteria naval architecture the time step imposed by the stability criteria (smallest elements) may be orders of magnitude smaller than the time (smallest elements) may be orders of magnitude smaller than the time step required to obtain time-accurate results (physical time step), step required to obtain time-accurate results (physical time step), rendering explicit schemes impractical. rendering explicit schemes impractical. -> Developed a new Predictor--> Developed a new Predictor-Corrector implicit-second-order-time-accurate methodCorrector implicit-second-order-time-accurate method
Pressure-Velocity segregation: Pressure-Velocity coupled schemes are Pressure-Velocity segregation: Pressure-Velocity coupled schemes are very expensive from a computational point of view (velocity and very expensive from a computational point of view (velocity and pressure discrete equations are coupled). However the use of standard pressure discrete equations are coupled). However the use of standard Pressure-Velocity segregation schemes impose strong limitations to the Pressure-Velocity segregation schemes impose strong limitations to the stability of the algorithm. stability of the algorithm. -> Developed a new implicit-second-order--> Developed a new implicit-second-order-time-accurate method based on a pressure-velocity segregation schemetime-accurate method based on a pressure-velocity segregation scheme
Stable algorithm: Stability of the numerical algorithm is still today an Stable algorithm: Stability of the numerical algorithm is still today an open issue. There is a need for an accurate, pressure and advection open issue. There is a need for an accurate, pressure and advection stable algorithm, based on the physics of the problem. stable algorithm, based on the physics of the problem. -> Developed a -> Developed a new stabilization methodology: Finite Increment Calculus based on the new stabilization methodology: Finite Increment Calculus based on the discrete balance of the quantitiesdiscrete balance of the quantities
Coupled free surface solver: Free surface condition must be coupled to Coupled free surface solver: Free surface condition must be coupled to the fluid flow solver in a stable and accurate way. the fluid flow solver in a stable and accurate way. -> Use of the -> Use of the transpiration technique.transpiration technique.
Numerical and Implementation Numerical and Implementation AspectsAspects
RANSE-NAVAL moduleRANSE-NAVAL module► RANSE and FS equations are integrated by RANSE and FS equations are integrated by
standard Finite Element Method (linear/quadratic standard Finite Element Method (linear/quadratic tetrahedra, hexahedra, prisms, …)tetrahedra, hexahedra, prisms, …)
► RANSE and FS solvers have been optimized for RANSE and FS solvers have been optimized for working with unstructured meshed of linear working with unstructured meshed of linear tetrahedra/trianglestetrahedra/triangles
► Implicit 2nd order time accurate fractional step Implicit 2nd order time accurate fractional step algorithm is used to go faster to steady statealgorithm is used to go faster to steady state
► Boundary conditions may be defined by analytical Boundary conditions may be defined by analytical functions (i.e. allowing to run different drifts functions (i.e. allowing to run different drifts angles with the same geometry/mesh)angles with the same geometry/mesh)
► RANSE-FS solver has been fully integrated within RANSE-FS solver has been fully integrated within the multi-physics environment Tdynthe multi-physics environment Tdyn
RANSE solver. Real Free Surface RANSE solver. Real Free Surface deformation and Sink and Trim deformation and Sink and Trim
treatment.treatment.
Free surface deformation as well as dynamic sinkage and trim angle are calculated during the program execution being boundary conditions and mesh automatically updated.Finally a new calculation is performed with the real geometry. This is done in four steps:1.New free surface NURBS definition, taking the resulting deformation into account, is generated:
• NURBS Cartesian support grid of MxN points is created.
• Z coordinate of the points, representing the wave elevation, is interpolated into the grid.
• Finally, the NURBS surface based on the support grid is generated.
2.Geometry of the vessel if moved according to calculated sinkage and trim angle. 3.New control volume and mesh are automatically generated. New mesh is generated with a quality criterion based on using an error estimator based on FIC technique.4.New calculation is carried out with fixed mesh
Numerical and Implementation Numerical and Implementation AspectsAspects
LINEAR moduleLINEAR module► FS - Potential flow equations are FS - Potential flow equations are
integrated by panel methodintegrated by panel method► The algorithm uses structured meshes of The algorithm uses structured meshes of
quadrilateral panels for free surface quadrilateral panels for free surface calculations calculations
► Boundary conditions are easily defined Boundary conditions are easily defined and automatically transferred to the meshand automatically transferred to the mesh
► Potential solver has been fully integrated Potential solver has been fully integrated within the multi-physics environment Tdynwithin the multi-physics environment Tdyn
9 kn
Application: IACC exampleApplication: IACC example
9 kn
Application: IACC exampleApplication: IACC example
Application: Rioja de EspañaApplication: Rioja de España► We present as example, the We present as example, the
Spanish America’s Cup boat Rioja Spanish America’s Cup boat Rioja de España, participant in the races de España, participant in the races of 1995of 1995
► POTENTIAL Flow simulations have POTENTIAL Flow simulations have been carried out with a symmetric been carried out with a symmetric full geometryfull geometry
► RANSE simulations have been RANSE simulations have been carried out at full scale, using a carried out at full scale, using a two layer k-e turbulence model, in two layer k-e turbulence model, in combination with an extended law combination with an extended law of the wallof the wall
► Results are compared to Results are compared to experimental data extrapolations experimental data extrapolations performed at El Pardo towing tank performed at El Pardo towing tank with awith a model at scale 1/3.5 model at scale 1/3.5
ApplicationApplication: Rioja de España: Rioja de España
Acknowledgements: Authors thank National Institute of Aerospace Technique (INTA) for permitting the publication of the towing tank tests of Rioja de España, and the model basin El Pardo (CEHIPAR) for sending the full documentation of the tests. Special gratefulness to IZAR shipbuilders for allowing the publication of the Rioja de España hull forms.
ApplicationApplication: Rioja de España: Rioja de EspañaExperimental dataExperimental data
TestTest GeometryGeometry Heel Heel angleangle
Drift Drift angleangle
C0D0C0D0 Hull, no Hull, no appendagesappendages 0º0º 0º0º
E0D0E0D0 Hull, bulb and keelHull, bulb and keel 0º0º 0º0º
E15D2E15D2 Hull, bulb, keel and Hull, bulb, keel and rudderrudder 15º15º 2º2º
E15D4E15D4 Hull, bulb, keel and Hull, bulb, keel and rudderrudder 15º15º 4º4º
E25D2E25D2 Hull, bulb, keel and Hull, bulb, keel and rudderrudder 25º25º 2º2º
Every case was towed at equivalent velocities of 10, 9, 8.5, 8.0, 7.5 and 7.0 knots
9 kn
Application: Rioja de EspañaApplication: Rioja de España
Longitudinal Wave Cut (8 Kn 0ºT 15ºH 2ºL)
-120
-100
-80
-60
-40
-20
0
20
40
60
80
-0.5 0 0.5 1 1.5 2
Adimensional LengthW
ave
Hig
th (
mm
)
EXPERIMENTAL
TDYNLIN
Longitudinal Wave Cut (8.5 Kn 0ºT 25ºH 2ºL)
-200
-150
-100
-50
0
50
100
-0.5 0 0.5 1 1.5 2
Adimensional Length
Wav
e H
igth
(m
m)
TDYNLIN
EXPERIMENTAL
ApplicationApplication: Rioja de España: Rioja de España
TestTest SymmetrySymmetry # Elements# Elements # Nodes# Nodes
C0D0C0D0 YesYes 300 000300 000 75 00075 000
E0D0E0D0 YesYes 700 000700 000 175 000175 000
E15D2E15D2 NoNo 1 500 0001 500 000 380 000380 000
E15D4E15D4 NoNo 1 500 0001 500 000 380 000380 000
E25D2E25D2 NoNo 1 500 0001 500 000 380 000380 000All grids used have been generated with the same quality criteria (in terms of size transition and minimum angle) and using element sizes from 5mm to 2000 mm.
All meshes have been generated with the same quality criteria (in terms of size transition and minimum angle) and using element sizes from 5mm to 2000 mm.
Application: Rioja de EspañaApplication: Rioja de España
E15D2 keel-bulb union detail
Final meshE0D0
E25D2 Final Mesh
E15D2 Initial mesh
Application: Rioja de EspañaApplication: Rioja de EspañaE25D2 Streamlines and E25D2 Streamlines and velocity modulus contours velocity modulus contours (V = 9 Kn)(V = 9 Kn)
Application: Rioja de EspañaApplication: Rioja de España
E25D2 Wave profile 9Kn
Experimental Simulation
ApplicationApplication: Rioja de España: Rioja de EspañaE25D2 Wave profiles and pressure contours 9Kn
ApplicationApplication: Rioja de España: Rioja de EspañaE0D0 Pressure contours 10Kn
ApplicationApplication: Rioja de España: Rioja de EspañaE25D2 Pressure contours and streamlines 9Kn
ApplicationApplication: Rioja de España: Rioja de España
E0D0 E15D2
E15D4
E25D2
CommentsComments► RANSE solver. Numerical results obtained in the analysis of America’s Cup RANSE solver. Numerical results obtained in the analysis of America’s Cup Rioja de EspañaRioja de España
boat indicate that Tdyn can be an useful tool for practical design purposes.boat indicate that Tdyn can be an useful tool for practical design purposes. Evaluation of total resistance gives less that 5% difference with towing tank Evaluation of total resistance gives less that 5% difference with towing tank
extrapolations in most part of the analysis range.extrapolations in most part of the analysis range. Evaluation of induced (lift) forces in non-symmetric cases gives even less differences.Evaluation of induced (lift) forces in non-symmetric cases gives even less differences. Obtained wave profiles are also very close to those measured in towing tank.Obtained wave profiles are also very close to those measured in towing tank. Qualitative results including: wave maps, streamlines, pressure and velocity contours Qualitative results including: wave maps, streamlines, pressure and velocity contours
and turbulence distribution, show also reasonable patternsand turbulence distribution, show also reasonable patterns► Numerical experience indicates that the RANSE formulation is very efficient for free Numerical experience indicates that the RANSE formulation is very efficient for free
surfaces flows, when the critical time step of the problem is some orders of magnitude surfaces flows, when the critical time step of the problem is some orders of magnitude smaller than the time step required to obtain time-accurate results - physical time step - smaller than the time step required to obtain time-accurate results - physical time step - (i.e. 4 CPU h / 1.5Mtetras standard PC single processor, including s&t final calculation – (i.e. 4 CPU h / 1.5Mtetras standard PC single processor, including s&t final calculation – use of a integrated Grid Computing System “ProcServer”).use of a integrated Grid Computing System “ProcServer”).
► Potential flow solver. Numerical results obtained in the analysis of America’s Cup Potential flow solver. Numerical results obtained in the analysis of America’s Cup Rioja de Rioja de EspañaEspaña boat indicate that the proposed method can be a useful tool for practical design boat indicate that the proposed method can be a useful tool for practical design purposes.purposes. Evaluation of wave resistance gives less that 5% difference with towing tank Evaluation of wave resistance gives less that 5% difference with towing tank
estimation in most part of the analysis range.estimation in most part of the analysis range. Evaluation of induced (lift) forces in non-symmetric cases gives even less differences.Evaluation of induced (lift) forces in non-symmetric cases gives even less differences. Obtained wave profiles are also very close to those measured in towing tank.Obtained wave profiles are also very close to those measured in towing tank. Qualitative results including: wave maps, pressure and velocity contours show also Qualitative results including: wave maps, pressure and velocity contours show also
reasonable patternsreasonable patterns► Potential flow solver is a very efficient tool for free surfaces flows. It can be used instead Potential flow solver is a very efficient tool for free surfaces flows. It can be used instead
of RANSE solver when local effect hasn’t interest for design (first stages of the design). of RANSE solver when local effect hasn’t interest for design (first stages of the design). Standard PC-CPU time required for one calculation is about 10 min.Standard PC-CPU time required for one calculation is about 10 min.
► Tdyn system has been used in the design of ALIGNHI and GBR America’s Cup boatsTdyn system has been used in the design of ALIGNHI and GBR America’s Cup boats
(Future) CFD Applications(Future) CFD Applications Highly accurate resultsHighly accurate results
Automatic mesh generation.Automatic mesh generation. Boundary layer simulation.Boundary layer simulation. Accurate turbulence models.Accurate turbulence models. Error estimation.Error estimation. Mesh refinement.Mesh refinement.
Automatic optimization of designAutomatic optimization of design Complex criteria (stability)Complex criteria (stability) Parametric geometry definitionParametric geometry definition Automatic geometry/mesh updateAutomatic geometry/mesh update
Coupled fluid-structure calculation (hydro-elasticity)Coupled fluid-structure calculation (hydro-elasticity) VPP-CFD tool (coupled)VPP-CFD tool (coupled)
Hydrodynamic flow. Free surface.Hydrodynamic flow. Free surface. Aerodynamic flow.Aerodynamic flow. Structural (membrane) analysis.Structural (membrane) analysis. Automatic mesh regeneration.Automatic mesh regeneration.
VPP-CFD tool in wavesVPP-CFD tool in waves Hydrodynamic flow. Free surface.Hydrodynamic flow. Free surface. Aerodynamic flow.Aerodynamic flow. Structural (membrane) analysis.Structural (membrane) analysis.
Small CPU time requirementsSmall CPU time requirements
further information at ...further information at ...
http://www.compassis.comhttp://www.compassis.com
http://www.gidhome.comhttp://www.gidhome.com
