Experimental Study of Irregular Wave Reflection by a Perforated Caisson Breakwater Under Wave Overtopping Conditions

The characteristics of irregular wave reflection by a perforated caisson breakwater under wave overtopping conditions were investigated using physical model tests. The effects of various parameters, especially the mean overtopping discharge that was mainly determined by the relative crest freeboard, on the reflection coefficient of perforated caisson breakwater were analyzed using experimental data. The results showed that the wave overtopping occurrence had no appreciable effect on the reflection coefficient when the mean overtopping discharge was less than 0.2 m3 (m s)−1. Under the wave overtopping condition, the reflection coefficient of the perforated caisson breakwater in this study was reduced by 20%–50% compared with that of the non-perforated caisson breakwater. A predictive formula of the reflection coefficient for perforated caisson breakwaters in terms of relative water depth, relative chamber width, and porosity of the caisson front wall, was developed for practical engineering design.