Advanced Applications in Naval Architecture Beyond the Prescriptions in Class Society Rules CAE Naval 2013, 13/06/2013 Sergio Mello Norman Neumann
Advanced Applications in Naval Architecture Introduction
Bureau Veritas Created in 1828 after the severe winter of 1821, which caused some 2,000 shipwrecks, 20,000 deaths and the bankrupt of most of insurance companies. Mission: keep underwriters up to date with the various premiums in use at different commercial centers and provide necessary information for determining the level of confidence in ships and equipment 3
Bureau Veritas 1829: First Register published with more than 10,000 ships "Nothing either in France or overseas can be compared to this manual (the Bureau Veritas Register) in any industrial branch, so absolutely necessary to the insurer and so useful to the maritime commerce in general. We do not understand how this institution does not benefit from the government s protection and solicitude for we consider it, beyond its usefulness, as being mainly of public interest." Underwriters' magazine "Revue des Assurances", 1830 Since then the role of the Class Societies has expanded and their contribution to the safety of navigation and operations in the sea is essential. Accidents may still occur, but we are convinced that we have avoided many others. 4
Bureau Veritas: The Rules Usually the Class Society verifies the conformity of ships design and maintenance state against Rules internally developed The Rules are updated or new Rules are developed to incorporate: New concept or significant change on operation mode is made; Results of research and development projects; Feedback of users (internal and clients); Accidents New concept or phenomenon Research and development Improvement of state-of-the-art Standardization 5
The Numerical Simulations inside Bureau Veritas Numerical Simulations are carried out normally as part of the independent verification process for classification or certification 6
The Numerical Simulations inside Bureau Veritas Some applications present particular issues sometimes not completely solved and therefore not covered properly in Rules, as for example: Behavior of water colunm inside moonpool or in confined area (gap between structures) Some applications are quite recent Monocolunm platform Side-by-side offloading for LNG Ultra-large vessels 7
Advanced Applications in Naval Architecture Ultra large vessels
The issue with ultra large vessels The hydro-structure problem is extremely complex 9
The classical approach The classical approach: Operation conditions Sea states RULES Linear hydrodynamic Problem Motions and accelerations Pressures Global loads Stresses Linear Structural model 10
The issue with ultra large vessels Ultra large ships are more flexible and the ship may suffer dynamic deformations due to the action of the waves o Whipping: transient vibration due to wave impact 11
The issue with ultra large vessels o Springing: resonant vibration of the structure when the natural modes match the encounter waves frequencies 12
The issue with ultra large vessels Our solution FE Model SPRINGING WHIPPING 13
The issue with ultra large vessels 14
The issue with ultra large vessels In case of whipping the local impact problem is solved and the nonlinear loads are included in a time domain scheme 15
The issue with ultra large vessels To validate our tools and methods we use model tests and full scale measurements 16
Advanced Applications in Naval Architecture Sloshing assessment
Sloshing Sloshing is probably the most complex hydro-elastic problem observed in the naval & offshore sector (Mark III type tank) 18
Sloshing assessment: our approach Our approach HYDRO-ELASTIC NUMERICAL METHODS HYDRO-ELASTIC IMPACT TESTS OPERATION & NAVIGATION CONDITIONS NUMERICAL SLOSHING SIMULATION IMPACT CONDITIONS & WAVE KINEMATICS HYDRO-ELASTIC NUMERICAL MODELS HYDRO-ELASTIC STRUCTURAL RESPONSE SMALL-SCALE SLOSHING MODEL TESTS CCS: FAILURE MODES, ULTIMATE STRENGTH CCS + INNER HULL: STRENGTH ASSESSMENT, ACCEPTANCE CRITERIA, SAFETY FACTOR HydroSTAR 19
Advanced Applications in Naval Architecture Water column behavior in confined areas
The water column behavior in confined areas A number of applications present confined water column 21
The water column behavior in confined areas The wave kinematics in confined area is very complex and at specific frequencies there may be a resonant phenomenon 22
The water column behavior in confined areas The resonance is a realistic phenomenon. However, the waves amplitudes at the resonance are not realistic since potential theory does not account for viscous dissipation. BV method (HydroStar) includes artificial dissipation in potential theory Linear dissipation F H 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 23
The water column behavior in confined areas 24
The water colunm behavior in confined areas However the dissipation in potential theory is artificial. The question is how to calibrate it: Model Tests CFD 25
Advanced Applications in Naval Architecture The ship energy efficiency
The ship energy efficiency Today there is a strong focus in improving energy efficiency of ships due to environmental (IMO requirements) and economical (price of bunker) concerns This improvement may be reached in several ways: o Improving hydrodynamic performance: o o o o Hull form; Saving devices; Propeller optimization; Operation conditions o o Changing the type of fuel (ex. lng); Optimizing the power generators 27
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 hull with 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 28
The ship energy efficiency: the optimization loop Automatic and efficient optimisation loop allowing evaluation of hundreds of hulls in few days Hull Modeling OPTNAV Automatic meshing Solvers : ICARE, ISIS, StarCCM+... Inputs Hull parameters Constraints Objectives Outputs Total drag, stability... Dedicated post-processing tools allowing simple visualisation and analysis by the client 29
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 Initial Optimised 30
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 31
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 32
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 33
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 34
Conclusions In naval and offshore Industry we are always at the edge of technology We have shown few examples of complex applications. There are a lot more... Our advice to the clients: WE WILL BE WITH YOU! 35