A Time-Domain Nonlinear Simulation Method for Wave-Induced Motions of a Floating Body

Abstract

A nonlinear calculation method based on the Mixed Eulerian Lagrangian method is presented for wave-induced motions of a 2-D floating body. Attention is placed on an effective calculation of the hydrodynamic force associated with the temporal derivative of the velocity potential in Bernoulli's pressure equation. Unlike other existing methods, the acceleration field can be computed simultaneously with the velocity field, which contributes greatly to reduction of the computation time. By use of Green's second identity, the new method is explained as an extension from the mode decomposition method, and close relations between the two methods are emphasized. Computations are performed for a wall-sided model and a flared model, and numerical results of the waves at upwave and downwave positions and the body motions (sway, heave, and roll) are compared with corresponding experiments. The overall agreement is very good, confirming validity of the present method. Discussion is also made on the parametric oscillation in roll, observed for the flared model.