Breaking Characteristics and Geometric Properties of Spilling Breakers over Slopes

Abstract

A two-phase flow CFD model based on the Reynolds-Averaged Navier–Stokes (RANS) equations coupled with the level set method (LSM) and k − ω turbulence model is used to simulate spilling breakers over a sloping bed. In order to validate the present numerical model, the simulated results are compared with the experimental data measured by Ting and Kirby (1996). The simulated horizontal velocities and free surface elevations are in good agreement with the experimental measurements. Moreover, the present model is able to model the prominent features associated with the breaking process such as the motion of air pockets in the water, formation of a forward moving jet, the splash-up phenomenon and the mixing of air and water in the breaking region. The numerical model has been utilized to study the influences of three important environmental parameters; water depth, offshore wave steepness and beach slope on the characteristics and geometric properties of spilling breakers over slopes. A total of 39 numerical experiment cases are performed to investigate the characteristics of breaking waves such as breaking location, incipient breaker height and water depth at breaking, incipient breaker indices and geometric properties with different offshore wave steepnesses at different water depths over a wide range of beach slopes. The geometric properties associated with breaking waves in shallow water are described using the wave steepness and asymmetry factors introduced by Kjeldsen and Myrhaug (1978). The computed results appear to give reasonable predictions and consistency with previous studies.