Steady streaming and flow turbulence in front of vertical breakwater with wave overtopping

In this paper, a two-dimensional Reynolds Averaged Navier Stokes model is developed to simulate the hydrodynamic process during the interactions between incident waves and vertical breakwaters. The numerical model considers both fully and partially standing wave cases due to wave overtopping. The turbulence field near the vertical breakwater is described by using a k-epsilon turbulence closure model and the free surface configuration is tracked by the Volume Of Fluid technique. To validate the numerical model, the results were compared with the experimental data of Xie (1981) [3] and Zhang et al. (2001) [5] and a very good agreement was observed between them. From the numerical results, it is concluded that there are major differences between the hydrodynamic characteristics in the two cases, whereby for the case of fully standing waves, the recirculating cells of steady streaming were clearly generated in front of vertical breakwaters. No recirculating cell was observed for the case of partially standing waves. The distribution of turbulence parameters, i.e. kinetic viscosity, turbulent kinetic energy, turbulent production, kinetic energy and turbulent energy dissipation rate were completely different in these two cases. In the partially standing waves, the turbulence parameters showed a considerable increase at the overtopping zone; however, the increasing of the turbulence production was very significant. It was also observed that for the case of partially standing waves the horizontal and vertical orbital velocities respectively at the anti-nodes and nodes were not close to zero as they were in the case of the fully standing waves. (C) 2010 Elsevier Ltd. All rights reserved.