GFD simulation of the interaction of large-amplitude ship motion with the large deformation of the free-surface

船舶在实际海况下的性能预报技术对船舶设计尤为重要。波浪在海面上是普遍存在的，船舶作大振幅、非线性运动。这严重影响了海上运输的经济性和安全性。本文以流体力学为基础，以贴体坐标系下的有限体积法为基本工具，采用密度函数技术来满足自由面条件，通过计算机模拟来预测船舶在波浪中的性能。将这些技术结合起来，模拟了最大振幅的纵摇和垂荡运动，具有足够的精度，与实验结果吻合良好。将该方法推广到斜波和行波中的运动。然而，值得注意的是，鲁棒性和稳定性的程度不是很令人满意。为此，本文发展了一种将矩形网格用于产生波浪的外部网格和船舶周围的边界拟合网格的重叠技术。用这种新方法模拟了六个自由度的所有运动。另一方面，另一种数值生成海浪的技术正在发展，这种模拟技术还没有完全发展到可以科普船舶在任何海洋环境中的任何运动。有些部分在不久的将来仍有待开发。然而，实质性的架构和组件是由这项研究工作完成的。

The technique to predict ship performance in actual sea condition is especially important for ship design. Waves always exist on the ocean surface and ships make large-amplitude, nonlinear motion. This gives serious influences on the economy and safety of sea transportation. The objective of this research is to develop such a technology to predict ship performance in waves by use of computer simulation based on fluid dynamics.The finite-volume method in the framework of the boundary-fitted coordinate system is chosen as a basical tool and the density function technique is introduced for the fulfillment of the free-surface conditions. With the combination of these technique the motions of largest amplitude such as pitching and heaving are simulated with sufficient degree of accuracy, having good agreement with experimental results. This method is extended to the motions in oblique waves and following waves. However, it is noted that the degree of robustness and stability is not very satisfactory. Therefore the overlapping technique is developed with the rectangular grids for the outer grids where waves are generated and the boundary fitted grids about a ship. With this new method all motions with six degrees of freedom are simulated. On the other hand another technique of numerically generating ocean waves is developed.The simulation technique is not fully developed to cope with any motion of a ship in any ocean circumstances. Some part is still left developed in the near future. However, the substantial architecture and components are completed by this research work.