A two-dimensional (2-D) numerical model is applied to study the wave reflection performance of perforated caisson breakwaters. The numerical model adopts a volume of fluid (VOF) method to track free surface and simulates the turbulent flow by using Reynolds Average Navier-Stokes (RANS) and k-ε turbulence model equations. The numerical results for the reflection coefficients of perforated caissons are in good agreement with the experimental data in literature, which means that the present numerical model can well estimate the hydrodynamic performance of complicated perforated thin wall structures. Numerical examples show that when the caisson porosity is fixed, the slit width in the perforated front wall has no significant influence on the reflection coefficient of perforated caisson breakwater. The effects of the slit width and the relative wave chamber width on the flow velocity and the turbulence kinetic energy are also discussed. It is found that the fluid flow through the perforated wall is in a form of jets and the turbulence kinetic energy is mainly concentrated around the region of the wave chamber.
A perforated caisson breakwater, containing a chamber between a perforated front wall and an impermeable back wall, has a good capability of reducing wave reflection and wave forces. The conception of the perforated wall breakwater was initially proposed by Jarlan (1961). Since then, research on wave interactions with perforated caisson structures has been ongoing. The relevant studies on the hydraulic performance of various types of perforated breakwaters have been reviewed by Huang et al. (2011).
Tanimoto et al. (1976) carried out earlier model tests to study the reflection of irregular waves by the perforated caisson breakwater. Kondo (1979) presented an analytical approach to estimate the reflection coefficient of a two-chamber perforated wall breakwater. Tanimoto and Yoshimoto (1982) theoretically and experimentally studied the reflection coefficient of a partially perforated caisson breakwater. Fugazza and Natale (1992) applied the potential flow theory to examine the reflection coefficients of perforated breakwater with multiple wave chambers. Using the Galerkin-eigenfunction method, Suh and Park (1995) developed an analytical model to predict the reflection coefficient of perforated caisson breakwater with a rubble mound foundation. Suh et al. (2001) theoretically investigated the reflection characteristics of irregular waves on perforated caisson breakwater. Ti et al. (2002) and Ti et al. (2003) used the matched eigenfunction expansion method to examine the oblique wave reflection by single-chamber and doublechamber perforated caisson breakwaters, respectively. Takahashi et al. (2003) employed a numerical technique to investigate the reflection coefficient of perforated caissons. Liu et al. (2007) studied the reflection coefficients of regular and irregular waves by a partially perforated caisson breakwater with a rock filled core. Lee and Shin (2014) earned out a three-dimensional model test to investigate the reflection coefficient of the perforated wall structure. Recently, Neelamani et al. (2017) carried out experimental tests to assess the wave reflection characteristics of a Jarlan-type breakwater with slotted walls.