Short-crested waves interaction with a concentric cylindrical structure with double-layered perforated walls

Abstract

This paper aims at extending the semi-analytical scaled boundary finite element method (SBFEM) to deal with the short-crested waves interaction with a surface-piercing concentric cylindrical structure, which consists of a solid inner cylinder and a coaxial double-layered perforated wall. The whole fluid domain is divided into three sub-domains including two bounded and one unbounded domains, and a variational principle formulation is used to derive the SBFEM equation in each sub-domain. Hankel functions and Bessel functions are chosen as the basis function for the solution of the unbounded and bounded domains, respectively. Although the structure adds a porous cylinder compared to that of Tao's work (2009), the SBFEM also needs to discretize only the outermost porous cylinder with curved surface finite-elements and keeps the radial differential equation solved completely analytically. However, the unknown coefficient vectors for solving the SBFEM equations increase compared with that of Tao's work. Thus we re-derive the solving process for the SBFEM equations. The results of numerical verification show that the present method yields excellent results with only a few nodes and quick convergence. The major factors including wave parameters and structure configuration that affect the wave forces, surface elevations and the diffracted wave contours are examined.