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© - Copyright Bureau Veritas
Advanced Applications in Naval Architecture
Beyond the Prescriptions in Class Society Rules
CAE Naval 2013, 13/06/2013
Sergio Mello
Norman Neumann
© - Copyright Bureau Veritas
Advanced Applications in Naval Architecture
Introduction
3© - Copyright Bureau Veritas
Bureau Veritas
►Created in 1828 after the severe winter of 1821, which caused some2,000 shipwrecks, 20,000 deaths and the bankrupt of most ofinsurance companies.
►Mission: keep underwriters up to date with the various premiums inuse at different commercial centers and provide necessaryinformation for determining the level of confidence in ships andequipment
4© - Copyright Bureau Veritas
Bureau Veritas
► 1829: First Register published with more than 10,000 ships
►Since then the role of the Class Societies has expanded and theircontribution to the safety of navigation and operations in the sea isessential. Accidents may still occur, but we are convinced that wehave avoided many others.
"Nothing either in France or overseas can be compared tothis manual (the Bureau Veritas Register) in any industrialbranch, so absolutely necessary to the insurer and so usefulto the maritime commerce in general. We do not understandhow this institution does not benefit from the government’sprotection and solicitude for we consider it, beyond itsusefulness, as being mainly of public interest."
Underwriters' magazine "Revue des Assurances", 1830
5© - Copyright Bureau Veritas
Bureau Veritas: The Rules
►Usually the Class Society verifies the conformity of shipsdesign and maintenance state against Rules internallydeveloped
► The Rules are updated or new Rules are developed toincorporate:
New concept or significant change on operationmode is made;
Results of research and development projects;
Feedback of users (internal and clients);
Accidents
New conceptor phenomenon
Research anddevelopment
Improvement ofstate-of-the-art Standardization
6© - Copyright Bureau Veritas
The Numerical Simulations inside Bureau Veritas
►Numerical Simulations are carried out normally as part of theindependent verification process for classification or certification
7© - Copyright Bureau Veritas
The Numerical Simulations inside Bureau Veritas
►Some applications present particular issues sometimes not completelysolved and therefore not covered properly in Rules, as for example:
►Some applications are quite recent
Behavior of water colunm inside moonpool or in confined area (gap between structures)
Monocolunm platform Side-by-side offloading for LNG Ultra-large vessels
© - Copyright Bureau Veritas
Advanced Applications in Naval Architecture
Ultra large vessels
9© - Copyright Bureau Veritas
The issue with ultra large vessels
► The hydro-structure problem is extremely complex
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The classical approach
► The classical approach:
Linear hydrodynamic Problem
Motions and accelerations
Pressures
Global loads
Linear Structural model
Stresses
Operation conditions
Sea states
RULES
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The issue with ultra large vessels
►Ultra large ships are more flexible and the ship may suffer dynamicdeformations due to the action of the waves
o Whipping: transient vibration due to wave impact
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The issue with ultra large vessels
o Springing: resonant vibration of the structure when the natural modesmatch the encounter waves frequencies
13© - Copyright Bureau Veritas
The issue with ultra large vessels
►Our solution
FE Model
SPRINGING
WHIPPING
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The issue with ultra large vessels
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The issue with ultra large vessels
► In case of whipping the local impact problem is solved and the non-linear loads are included in a time domain scheme
16© - Copyright Bureau Veritas
The issue with ultra large vessels
► To validate our tools and methods we use model tests and full scalemeasurements
© - Copyright Bureau Veritas
Advanced Applications in Naval Architecture
Sloshing assessment
18© - Copyright Bureau Veritas
Sloshing
►Sloshing is probably the most complex hydro-elastic problem observedin the naval & offshore sector (Mark III type tank)
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Sloshing assessment: our approach
►Our approach
CCS + INNER HULL:STRENGTH ASSESSMENT,ACCEPTANCE CRITERIA,
SAFETY FACTOR
SMALL-SCALESLOSHING
MODEL TESTS
NUMERICALSLOSHING
SIMULATIONIMPACT CONDITIONS & WAVE KINEMATICS
HYDRO-ELASTICSTRUCTURAL
RESPONSE
HYDRO-ELASTIC IMPACT TESTS
CCS:FAILURE MODES,
ULTIMATE STRENGTH
HYDRO-ELASTICNUMERICAL METHODS
HYDRO-ELASTIC NUMERICAL MODELS
OPERATION& NAVIGATIONCONDITIONS
HydroSTAR
© - Copyright Bureau Veritas
Advanced Applications in Naval Architecture
Water column behavior in confined areas
21© - Copyright Bureau Veritas
The water column behavior in confined areas
►A number of applications present confined water column
22© - Copyright Bureau Veritas
► The wave kinematics in confined area is very complex and at specificfrequencies there may be a resonant phenomenon
The water column behavior in confined areas
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► The resonance is a realistic phenomenon. However, the wavesamplitudes at the resonance are not realistic since potential theorydoes not account for viscous dissipation.
►BV method (HydroStar) includes artificial dissipation in potential theory
The water column behavior in confined areas
FH
• Linear dissipation
• Expression for the velocity potential
• Integral equation extended to a part of the free surface
Classical on body hull
Need to remove irr. Freq.
New over the damping zone
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The water column behavior in confined areas
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►However the dissipation in potential theory is artificial. The question ishow to calibrate it:
The water colunm behavior in confined areas
Model Tests CFD
© - Copyright Bureau Veritas
Advanced Applications in Naval Architecture
The ship energy efficiency
27© - Copyright Bureau Veritas
► Today there is a strong focus in improving energy efficiency of shipsdue to environmental (IMO requirements) and economical (price ofbunker) concerns
► This improvement may be reached in several ways:
o Improving hydrodynamic performance:
o Hull form;
o Saving devices;
o Propeller optimization;
o Operation conditions
o Changing the type of fuel (ex. lng);
o Optimizing the power generators
The ship energy efficiency
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The ship energy efficiency
►Bureau Veritas has established a partnership with the French specialized firm HydrOcean in order to perform hydrodynamic optimization: Of the hull forms (optimization on
10 to 30 hull forms)
Of the propeller design (CFD)
Of the overall efficiency of the hullwith rotating propeller behind and rudder in the wake of the propeller (CFD)
Of various types of energy saving devices (special designs of propellers, podded propellers, contrarotating propellers, fins, aft bulbs, ducts)
Example of bulb deformations generated with OPTNAVc
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The ship energy efficiency: the optimization loop
Hull Modeling OPTNAV
Automatic meshingSolvers :
ICARE, ISIS, StarCCM+...
OutputsTotal drag, stability ...
InputsHull parameters
Constraints Objectives
Automatic and efficient optimisation loop allowing evaluation of hundreds of hulls in few days
Dedicated post-processing tools allowing simple visualisation and analysis by the client
30© - Copyright Bureau Veritas
The ship energy efficiency: bare hull optimization
►Description : CFD with free surface simulations of the hull
►Outputs of the simulations :
Ship drag issued from initial hull
Sinkage and trim
Wave field, nominal wake …
►Example of applications :
Hull drag reduction and form optimisation
Wave field reduction
InitialOptimised
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The ship energy efficiency: self propulsion simulations
►Description : unsteady CFD simulations of hull and appendages, including rotating propeller
►Outputs of the simulations :
Propulsive performances of the ship
Evaluation of hull / propeller / appendages interactions
Cavitation onset risk, pressure pulses …
►Example of applications :
Hull power optimization
Appendages alignment (twisted rudder and shaft brackets …)
Evaluation of several propellers performances
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The ship energy efficiency: open water simulations
►Description : unsteady CFD simulations of a rotating propeller
►Outputs of the simulations :
Kt, Kq and efficiency of the propeller in open water
Estimation of cavitation onset risks
►Example of applications :
Evaluation of propeller performances
Evaluation Energy Saving Devices close to propeller
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The ship energy efficiency: saving devices evaluation
►Description : unsteady CFD simulations with or without rotating propeller
►Outputs of the simulations :
Kt, Kq and efficiency of the propeller with or without ESD
Ship drag with or without ESD
►Example of applications :
Evaluation of hull or propeller with and without ESD
Evaluation of hydrodynamic loads for structural design
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The ship energy efficiency: SEECAT
►All the results can be integrated in our SEECAT tool in order to simulate, through holistic approach, the energy flow of the ship
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► In naval and offshore Industry we are always at the edge of technology
►We have shown few examples of complex applications. There are a lotmore...
►Our advice to the clients:
Conclusions
WE WILL BE WITH YOU!