时域匹配直接边界元方法及其数值特性

Study on the numerical characteristics of time domain matching direct boundary element method

为了解决时域格林函数方法在计算非直壁浮体的数值发散问题,基于三维势流理论,对时域匹配直接边界元方法的数值特性进行了系统研究.该方法在流场中引入匹配控制面,将流场划分为内域和外域,内域中采用简单格林函数直接边界元方法,外域中采用满足线性自由面条件的时域格林函数方法,进行浮体时域水动力计算.研究结果表明:该方法外传波浪效率高,时域长期模拟结果稳定.基于同一网格模型,可以准确模拟不同波浪条件下浮体的时域水动力,无需重新划分网格,且网格数量大幅减少.

This paper presents an examination of the numerical characteristics of the time domain matching direct boundary element method, which is based on the three dimensional potential flow theories, to solve the numerical divergence problem of the time domain Green function method for calculating hydrodynamics of the non-sided-wall floating body. The control matching surface was introduced to flow field to decompose the flow field into the inner and outer domains. The simple Green function direct boundary element method was employed in the inner domain, and the time domain Green function method, which satisfies the linearized free surface condition, was applied in the outer domain. The time domain hydrodynamics of floating body was calculated. The results show the present method can transmit disturbing waves with high efficiency, and produce stable numerical results for longer simula- tions. Furthermore, based on the same grid model, the present approach can accurately evaluate the hydrodynamic problems of floating body under different wave conditions without re-meshing model in time domain, and the number of mesh grids substantially decrease.