WAVE SCATTERING BY SUBMERGED POROUS DISK

Linearized potential wave theory is applied in the present paper to in vestigate the phenomenon of wave scattering by a submerged porous disk . By means of the eigenfunction expansion method, harmonic expressions of the velocity potential in terms of unknown constants are obtained in two subregions of the domain by taking into account the boundary co nditions on the free surface, the porous disk surface, and sea bottom surface, as well as the Sommerfeld condition at infinity. These unknow n constants are then determined by the matching conditions. Variation of the wave height around the disk and the wave load on the disk versu s the dimensionless disk radius, the relative water depth, and the por ous-effect parameter is discussed. It is found that the wave scatterin g by a disk includes a process of focusing wave energy near the rear o f the disk for small dimensionless porous-effect parameters. An increa se of the dimensionless porous-effect parameter decreases the wave hei ght, and the behavior of a porous disk is similar to that of a wave ab sorber that may lead to setdown for a large disk radius.