Characteristics of the wave reflection due to the composite breakwater

This paper examines the reflection characteristics of normally incident waves acting on the composite breakwater, which is composed of the elastic membrane and the submerged breakwater. Based on small amplitude wave theory, the numerical calculation model is constructed by using the eigenfunction expansion method. Several factors of reflection characteristics, such as the width of the composite breakwater, height of the submerged breakwater, pretension of the elastic membrane and mass are considered for further analysis. Results show that for long period waves, both effects of pretension and mass of the elastic membrane are not dominant; however, when the ration of bank width to water depth, l/h, is equal to 1.0, and the coefficient of the submerged breakwater height, q', is equal to 0.9, the reflection effect of the composite breakwater is quite better. In the contrast, for short period waves, when l/h =1.0, q'=0.7, pretension T'=0.002, and mass m'=0.2, the reflection of the composite breakwater shows dominant effect.