The Reflection of Normal Incident Waves by Absorbing-Type Breakwaters

摘要

This paper investigates the reflection of normal incident waves produced by absorbing-type breakwaters.The absorbing-type breakwaters in this study consist of a vertical porous plate,a submerged permeable caisson,and an impermeable back wall.The flow field is divided into four regions:a porous caisson region,and three pure water regions.Under the assumptions of linear wave theory,Darcy's law in the perforated wall,and the pore velocity potential theory of Sollitt and Cross (1972) in the porous caisson region,this study creates a 2-D BEM model to calculate the reflection coefficients of water waves using several breakwater properties.This numerical model is calibrated by previous numerical studies and limiting cases for a partially perforated-wall caisson breakwater and a vertical porous breakwater with an impermeable back wall.Generally speaking,the wave dissipation in absorbing-type breakwaters is bigger than that for a partially perforated-wall caisson breakwater.The reflection coefficient values imply the performance of wave absorbers in this study.Therefore,we examine the major factors that affect the reflection coefficient.