On the Reverse Flow Beneath a Submerged Plate Due to Wave Action

Abstract

A water wave, passing over a horizontal plate submerged beneath the free surface, would experience above the plate both a change in wave height and wavelength. On leaving the plate, the wave, in general, encounters a reduction in wave height as compared to the incident wave. The reduction in the wave height depends upon the wavelength, the plate length and its position below the free surface, i.e., the submergence depth, as well as the water depth. Depending on the particular flow configuration, a pulsating reverse flow can occur beneath the plate, in a direction opposite to that of wave propagation. This pulsating two-dimensional flow field has been proposed by others as a method to convert wave energy into electrical energy. The main objective of this paper is to study the reverse flow beneath a submerged plate by surface wave action in finite water depth. A 2-D numerical model that uses the boundary-element method is developed to simulate this physical event by solving the linear equations of motion for waves in an ideal fluid. In addition, the Reynolds-Averaged Navier-Stokes equations are used to solve the nonlinear equations of motion for waves in a viscous fluid by use of the Fractional-Step Method. The numerically obtained linear and nonlinear results are compared with the available experimental data.