Harsh sea conditions constitute a major threat to the safety of shipping and floating body. In this study, a fully nonlinear boundary element method has been introduced to solve the hydrodynamic properties of a container ship. A mixed Euler-Lagrange method is utilized to calculate the velocity on free surface and further update the wet surface in each time step, which make capturing the transient free surface possible even when the hull motion is large. To avoid the instability from temporal difference method and enhance the accuracy of program, we introduce the concept of acceleration potential to solve the time derivative term of velocity potential. The experimental measurements of the load response in regular wave were used to validation, and good agreements were achieved. The influence of wave direction and ship speed with corresponding nonlinear phenomenon are discussed in this study. The time consumed for each time step is also given in this study, implied that BEM method is efficient and suitable to solve the hydrodynamic problem.
This paper aims to explore the nonlinear hydrodynamic characteristics of a ship travelling in waves with forward speed under the frame of potential flow. We take advantage of time domain Rankine source method to deal with the transient problem. Such method is widely used in wave-body interaction problem (Feng et. al., 2016), body-body interaction problems (Graefe et. al., 2013; Yuan et. al., 2016); water entry problems (Sun et. al., 2019). Rankine type Green's function is also suitable for nonlinear issue especially for moving body with large motion. Shao and Faltinsen (2012) presented the linear seakeeping formulation and calculated the added resistance and body motion of a ship. Zhang and Beck (2007) studied the 2D large motion oscillation and impact problem by using linearized boundary conditions. He and Kashiwagi (2014) researched the radiation and diffraction problem for modified Wigley model. The Rankine source dissatisfies with any boundary conditions, all the surface within the closed domain have to be panelized. Among many different discretization schemes, the boundary element method has obvious advantages in terms of the reduced dimension. We also use parallel code to further improve the calculation efficiency.
