Effects of a thin vertical porous barrier on the water wave scattering by a porous breakwater

Abstract

Porous breakwaters are introduced to reduce the impact of wave load on various marine structures and dissipate unwanted wave energy by creating a tranquility zone. This type of marine structure can have practical implications for the development of artificial breeding or nursing grounds for fish and other sea animals. We theoretically investigated the water wave scattering by a surface-piercing porous breakwater in the presence of a thin vertical porous barrier in the framework of linear potential flow theory. Flow through the vertical porous barrier is considered using the model of Yu [“Diffraction of water waves by porous breakwaters,” J. Waterw., Port, Coastal, Ocean Eng. 121, 275–282 (1995)] under the assumption of fine pores. We use the eigenfunction expansion method to obtain solutions of the associated boundary value problems analytically. We develop semi-analytical solutions of the proposed mathematical problem using matching boundary conditions along boundaries of individual successive regions of the system. For wave scattering by a barrier-breakwater system with focus on wave energy dissipation, the effect of various wave and structural parameters on the reflection and transmission coefficients, dissipation coefficient, and wave force on the system are studied. The practical interest in this problem stems from the result that for the barrier-breakwater system, there exists a critical value of wave inclination angle below which wave reflection is minimum and wave energy dissipation is maximum. The results have implications for the proposed problem to harness energy from ocean waves and other problems related to the design and enhancement of the hydrodynamic performance of the breakwater in the marine environment.