Numerical study on the wave dissipating performance of a submerged heaving plate breakwater

Abstract

The purpose of this paper is to give a new explanation for the wave dissipating mechanism of a heaving plate breakwater from the perspective of vortex kinematics. A high-order finite difference method, the constrained interpolation profile (CIP)-based model is used to numerically investigate the wave dissipating performance of a submerged heaving plate breakwater, in which the tangent of hyperbola for interface capturing/slope weighting (THINC/SW) is adopted for the free surface/interface capturing, and an immersed boundary method (IBM) is employed to treat the motion of the heaving plate. Two-dimensional simulations of wave-plate interactions are conducted and the results are assessed via comparing with numerical and experimental results available in previous literature. The results of plate hydrodynamics and vortex kinematics around a heaving plate are presented in terms of the reflection, transmission and dissipation coefficients, wave amplitude spectrums, vorticity field evolutions, trailing vortices trajectories and averaged velocity fields. The results of a fixed plate are also presented for comparison. It is found that the heaving motion of plate changes the direction of the downstream jet flow and trailing vortex shedding trajectories, which strongly enhances the wave dissipating performance of a heaving plate. The effects of the relative plate width B/L (B is the width of the plate and L is wave length) on the wave dissipating performance of a heaving plate is also considered. Results show that a heaving plate breakwater is better for the block of medium and short waves.