应用混合格林函数法计算波浪中浮体运动及离散参数取值的算例分析

Analysis of Motions of Floating Body in Waves by Hybrid Green Function Method and Discretization of Parameters

通过假想的直壁控制面将流场分割成内域和外域,分别引入Rankine源和自由面Green函数并结合控制面上的连续条件进行耦合求解,应用混合格林函数法对浮体在波浪中的运动进行了时域计算。以wigley型船为例,针对不同的时间步长、自由面和控制面的不同区域范围、面元划分的不同密度等进行了一系列数值计算和比较,讨论了离散区域大小、网格密度等参数对计算结果的影响,并给出其合理的取值范围。在此基础上,对一艘LNG船在不同浪向入射波中的运动响应进行计算,并与试验数据对比。结果证明,该方法能有效解决外飘船型时域计算的发散问题,可以对浮体在斜浪中的运动进行时域模拟。

In order to simulate motions of floating body in oblique waves, a hybrid Green function method in time domain is employed. Fluid filed is decomposed into inner and outer domain by an imaginary control surface. Rankine source method is applied in the inner domain, while transient Green function method is used in the outer domain. Based on a series of numerical calculations for a Wigley-hull ship, influences of time step, discretization of both free surface and control surface on the solution are discussed and a reasonable value range of the parameters is given out. Motions of a LNG ship in waves are calculated, and the numerical results agree well with the experimental data. It is shown that present method is effective in simulating motions of floating body in oblique waves.