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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


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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 of insurance 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


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Bureau Veritas

1829: First Register published with more than 10,000 ships

Since then the role of the Class Societies has expanded and their

contribution 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 governmentsprotection and solicitude for we consider it, beyond its

usefulness, as being mainly of public interest."Underwriters' magazine " Revue des Assurances" , 1830


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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


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The Numerical Simulations inside Bureau Veritas

Numerical Simulations are carried out normally as part of theindependent verification process for classification or certification


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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


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Ultra large vessels


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The issue with ul tra 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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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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o Springing: resonant vibration of the structure when the natural modesmatch the encounter waves frequencies


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Our solution

FE Model

SPRINGING

WHIPPING


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In case of whipping the local impact problem is solved and the non-linear loads are included in a time domain scheme


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To validate our tools and methods we use model tests and full scalemeasurements


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Sloshing assessment


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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-SCALE

SLOSHING

MODEL TESTS

NUMERICAL

SLOSHING

SIMULATION

IMPACT CONDITIONS

& WAVE KINEMATICS

HYDRO-ELASTIC

STRUCTURAL

RESPONSE

HYDRO-ELASTIC

IMPACT TESTS

CCS:

FAILURE MODES,

ULTIMATE

STRENGTH

HYDRO-ELASTIC

NUMERICAL

METHODS

HYDRO-ELASTIC

NUMERICAL MODELS

OPERATION

& NAVIGATION

CONDITIONS

HydroSTAR


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Water column behavior in confined areas


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The water column behavior in confined areas

A number of applications present confined water column


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The wave kinematics in confined area is very complex and at specificfrequencies there may be a resonant phenomenon



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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


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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However the dissipation in potential theory is artificial. The question ishow to calibrate it:

The water colunm behavior in confined areas

Model Tests CFD


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The ship energy efficiency


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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



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Bureau Veritas has established a partnership with theFrench specialized firm HydrOcean in order to performhydrodynamic optimization:

Of the hull forms (optimization on10 to 30 hull forms)

Of the propeller design (CFD)

Of the overall efficiency of the hullwith rotating propeller behindand rudder in the wakeof the propeller (CFD)

Of various types of energy savingdevices (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

OPTNAVAutomatic meshing

Solvers :

ICARE, ISIS, StarCCM+...

Outputs

Total drag, stability ...

Inputs

Hull parameters

Constraints

Objectives

Automatic and efficient optimisation loop allowing

evaluation of hundreds of hulls in few days

Dedicated post-processing toolsallowing simple visualisation and

analysis by the client


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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 rotatingpropeller


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


Kt, Kq and efficiency of the propeller in open water

Estimation of cavitation onset risks


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


Kt, Kq and efficiency of the propeller with or without ESD

Ship drag with or without ESD


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, throughholistic 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!

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