PREDICTION OF SHIP RESPONSE STATISTICS IN EXTREME SEAS USING MODEL TEST DATA AND NUMERICAL SIMULATIONS BASED ON THE RANKINE PANEL METHOD

摘要

Earlier investigations have indicated that proper prediction of non-linear response due to non-linear waves is important for ship safety in extreme seas. Nonlinearities may increase significantly ship response in steep sea-states. The topic has not been sufficiently investigated yet, particularly when rogue waves are considered. A question remains whether the existing linear codes can predict nonlinear responses with a satisfactory accuracy and how large the deviations from linear predictions are. To indicate it, response statistics have been studied based on the model tests carried out in the Spanish basin CEHIPAR and the sea-keeping tank of the Technical University of Berlin (TUB), and compared with the results derived from numerical simulations using the DNV code WASIM. It is a potential code for wave-ship interaction based on 3D Panel method, which can perform both linear and nonlinear simulations. The numerical simulations with WASIM and the model tests including extreme and rogue waves have been performed on 3 different ship types: Chemical tanker, LNG tanker and a Cruise ship. The analysis includes both regular and irregular waves. Ship motions and bending moments have been studied. The effect of water depth on ship responses is also investigated. The study indicates that nonlinearities may have significant impact on extreme motions and bending moment induced by strongly nonlinear waves. Uncertainties related to the results are also discussed.