Numerical simulation on hydrodynamic performance of perforated caisson breakwater with slotted shoreward wall

Abstract

The purpose of this study is to investigate wave reflection and overtopping of perforated caisson breakwater with a slotted shoreward wall (PCB–S) under regular wave conditions. A numerical wave tank, solving the two-dimensional Reynolds-averaged Navier-Stokes equations with the k-ω turbulence closure and employing the VOF model for free surface capturing, is validated against experiments. The study thoroughly explores the influence of various factors, such as wave steepness, front wall porosity, relative wave chamber width, submergence depth of the shoreward wall slot, and shoreward wall porosity, on the reflection coefficient, wave overtopping discharge, and exit flow velocity. The distribution of vorticity and turbulent kinetic energy around PCB-S were clarified to better understand wave dissipation mechanism. The results show that the PCB-S improves the water exchange between the inside and behind the caisson and effectively reduces the reflection coefficient and the overtopping discharge. The simulation results pointed out that the relative wave chamber width B/L = 0.1, the relative submergence depth of the slot s/d = 0.33–0.42, and the porosity of the shoreward wall ε2 = 0.1–0.12 are most conducive to the reduction of the reflection coefficient of the waves.