Study on Ship Motions Based on Three Dimensional Nonlinear Multi-domain Method

Based on three-dimensional potential flow theory in the time domain, a nonlinear multi-domain method is established to calculate ship motions in waves. The computation domain is divided into the inner domain and outer domain with an imaginary control surface. In the outer domain, the transient Green's function method is adopted. In the inner domain, the Rankine source method is used, in which the boundary condition on the free surface is linearized to guarantee the continuity of the potential and its derivative on the control surface, and a transition function is introduced. Coupled boundary integral equations are solved in both inner and outer domain to obtain the disturbance velocity potential and induced hydrodynamic forces. Incident wave forces and restoring forces are computed on transient wet surface. Motion of a math ship model Wigley-3 is calculated with the present method. Factors affecting the convergence of the computation are discussed, and accuracy and reliability of the present method and program code are validated. Motions of practical ships with flares in series 60 and series 175 are calculated. The results are compared with experiment and that obtained with other methods. Advantage of the three-dimensional nonlinear multi-domain method in forecasting practical ship's motion is validated. © 2020, Editorial Office of Ship Building of China. All right reserved.