A Numerical Wave Tank (NWT) for 3-D problems is developed. The motion of an ideal fluid and the motion of a floating body are simulated in a time domain. The Boundary Value Problems (BVP) for velocity field and acceleration field are solved taking into account the interaction between the fluid and floating body motions. The Quadratic Boundary Element Method (QBEM) is used to solve these fields. Implicit boundary condition method is used for the acceleration field. Time integration is carried out with the 4th order Runge-Kutta method (RK4). Free surface is updated with the Semi-Lagrangian time marching scheme. A double-node technique is used to properly update the intersections between the free surface and the body. Some calculations are carried out by the newly developed 3-D NWT and the following three cases are presented in this paper i. The simulation of 3-D waves in a circular wave basin. 2. The simulation of hydrodynamic forces on a sphere in forced heave motion. 3. The simulation of the free heave motion of a sphere in a circular wave basin.
The accurate prediction of wave-induced motions of floating structures and hydrodynamic forces acting on their hulls are one of the main concerns in ocean engineering. When the amplitude of waves and body motions are large in rough seas, nonlinear effects become large. To predict these motions and forces, fully nonlinear Numerical Wave Tanks (NWT) have been developed by many researchers in the past decade based on the pioneer work of Longuet-Higgins and Cokelet (1976). Kim et a1.(1999) summarized recent studies on the use and development of NWT. These studies on the motion of a free-floating body are reviewed here. Vinje and Brevig (1982), Cointe et a1.(1991) decomposed acceleration field into 4 modes and simulated the motion of a 2-D floating body.