Simulation of waves group propagation and breaking in coastal zone using a Navier–Stokes solver with an improved VOF free surface treatment

Oceans and seas, which cover a large percentage of the Earth, interact with the atmosphere at their upper boundary. The generation, growth and breaking of wind waves are the most prominent physical processes that occur at water surface. In this study the transformation of waves groups in a medium water of coastal zone towards breaking point is investigated in two dimensional case. The governing equations are Navier–Stokes, continuity and Fractional VOF function equations. The fluid flow is assumed to be viscous and incompressible, and the turbulence effect has been considered in wave evolution using a two equation k–εk–ε model. The DDAR–VOF method which is a kind of SLIC method defined by Moradi [Moradi Larmaei M, Simulation of waves groups propagation and breaking in medium water depth using VOF method. M.Sc. thesis (Distinct). Iran: Amirkabir University of Technology; 2006] is used by employing a finite volume method based on the PISO algorithm. To validate the numerical model, different tests such as led-driven cavity, a simple translation test, rotation test, dam-break, turbulent pattern and plunging breaking are performed. These tests show that this model is a powerful and reliable tool to simulate free water surface in wave motion with breaking process. The numerical results obtained indicate the existence of the waves group inducing set-down in the form of long wave in a medium water depth due to passage of high waves group. Comparison of the results with the experimental data shows that the current modified model is able to predict this complicated phenomenon accurately.