Nonlinear Wave-Body Interactions for Arbitrarily Shaped Body Using 3D Numerical Wave Tank

Abstract In this study, general hydrodynamic performances of two different types of floating foundations, vertical cylinder and that with roof buoy, for power generation by multiply-stacked LEGs (linear electricity generators). Their hydrostatic capability and body motions in waves are analyzed and systematically compared. Those results were obtained by using three independent computer programs, commercial WAMIT as linear frequency-domain calculation and commercial OrcaFlex and in-house NWT (numerical wave tank) programs for time-domain linear and body-nonlinear simulations. The numerical results from the three independent programs generally agree well. The cylinder with roof buoy has twice as larger hydrostatic pitch restoring moment than that of vertical cylinder alone so that the increased destabilizing moment caused by more sliding magnets can be overcome. The roof-buoy also significantly increases nonlinear Froude-Krilov pitch exciting moment compared to vertical cylinder to enhance power generation in relatively low sea states. The body-nonlinear simulations can be appreciably different from the linear simulation especially for the hull shape with roof buoy.