Numerical Simulations for Highly Nonlinear Behavior of a Ship in Large-Amplitude Waves

(1)编制了气液固多相流数值计算程序。该程序以CIP-CUP方法为基础，具有数值扩散小、能同时求解可压缩流体和不可压缩流体的特点。作为对程序的检验，对波浪冲击问题进行了研究，发现即使在破碎和飞溅发生的情况下，该程序也是非常通用的。(2)对静水上固定的平台在大振幅孤波作用下产生的冲击压力和合力进行了数值计算和实验比较。不仅对于这种情况，而且对于进入L结构甲板上的绿水与甲板上的反射波之间的复杂相互作用，都得到了很好的吻合。(3)建立了数值波浪水池，安装了柱塞式或襟翼式造波机，并设置了数值吸波滩来防止波浪反射。然后在该数值波浪水池中对大振幅波浪作用下浮体的非线性运动进行了数值模拟。验证了漂移力和脉冲波浪力的计算是成功的，且计算方法具有很强的通用性。(4)利用三维时域格林函数法，研究了所谓的船体非线性计算方法。即使是在船首有火炬的情况下，也成功地模拟了波浪诱导的运动和波浪中的附加阻力，计算结果与实验结果吻合较好。

(1) A numerical calculation program was developed for simulating the multi-phase flow with gas, liquid and solid. This program is based on the CIP-CUP method, which is featured in less numerical diffusion and being capable of solving the compressible and incompressible fluids simultaneously with the same equations. The wave impact problem was studied as a check of the program and we found the program very versatile even for the breaker and splash occurring.(2) Comparison between numerical results and corresponding experiments was made for the impulsive pressure and resultant force acting on a platform fixed above the still water due to a large-amplitude soliton wave. Good agreement was confirmed not only for this case but also for complicated interactions between the green water coming onto the deck of a L-shaped structure and the reflected waves on the deck.(3) A numerical wave tank was established, with a plunger-type or flap-type wavemaker installed and the numerical absorbing beach to prevent the wave reflection. Then numerical simulations were performed in this numerical wave tank for the nonlinear motions of a floating body caused by large-amplitude waves. It was confirmed that the drift force and impulsive wave force were successfully computed and the computations were very versatile.(4) By means of the 3-D time-domain Green function method, the so-called body nonlinear calculation method was studied. The wave-induced motion and the added resistance in waves were successfully predicted even for an actual ship with flare near the bow, which was found to be in good agreement with experiments.