Trapping of surface waves by porous and flexible structures

Abstract

The trapping of surface waves by submerged vertical porous and flexible barriers near the end of a semi-infinitely long channel of finite depth is investigated. The barrier configurations include a bottom-touching barrier and a surface-piercing barrier. In the case of a bottom-touching barrier, the barrier is clamped at the bottom and is free at the upper end. While in the case of a surface-piercing barrier, the barrier is clamped by a structure above the free surface and is free at the lower end which is inside the water. By matching the velocity and pressure along the barrier and along the gap and using the edge conditions at the end points, systems of linear equations are obtained. In the case of a surface-piercing barrier, the deflection, slope of deflection, the bending moment and the shear force acting on the barrier are assumed to be continuous at the interaction point where the barrier and the free surface meet each other. The reflection coefficients are obtained and discussed for various wave conditions, geometrical settings, and barrier properties. The hydrodynamic force and the overturning moment on the barrier and the deflection of a flexible barrier are calculated and analysed for different cases.