二阶Stokes波对多个水平平行柱体的垂向绕射

Diffraction of second order Stokes wave for multiple horizontal cylinders

为了求解二阶Ｓｔｏｋｅｓ波对多个水平平行柱体垂向绕射问题的频域解，在内场中使用了简单Ｇｒｅｅｎ函数的边界元方法与外场的特征函数展开式相结合的方法，导出了有限深水域中二维二阶绕射势在外场的解析表达式，对绕射波的远场反射与透射特性给予清晰的物理解释。利用摄动展开数值求解了流场的二阶绕射势和各个剖面所受的一、二阶波浪力。与单个剖面的情况相比，数值结果证实了多个剖面引起的绕射问题会产生诸如水波共振等水动力干扰现象，这对于多体结构的锚泊系统和其它海洋工程设备的设计是很重要的。

Two dimensional diffraction problem for multiple horizontal cylinders of the second order Stokes waves is treated in frequency domain based on the boundary element method using simple Green's function in inner water region combined with the eigenfunction expansions in outer water regions. The analytical expression of second order diffraction potential in the outer regions of finite water depth gives a clear physical meaning of wave transmission and reflection characteristic in the far field. By perturbation method the numerical results are provided for the second order diffraction potentials and wave forces on each cylinder. Compared with the case of single isolated cylinder, hydrodynamic interference phenomena, such as wave resonance etc, of the diffraction problem due to multiple cylinders are identified, which is important to the design of moorings and other facilities involving multiple structures.