Numerical Modelling of a Solitary Wave Propagating over a Submerged Rectangular Breakwater

Abstract

Three-dimensional numerical simulation is carried out to reproduce the turbulent flow induced by the solitary wave passing a bottom-mounted, submerged, rectangular breakwater. The flow is characterized by the two counter-clockwise rotating vortices massively separated from the upstream edge and the downstream end of the top face of the submerged rectangular obstacle, respectively, and a clock-wise rotating vortex emerged at the junction of the channel bottom and the downstream face of the obstacle. It is crucial to accurately resolve the boundary layer separations at the obstacle surface and the channel bottom both upstream and downstream of the obstacle for elucidating the complex dynamics of resulting turbulent vortical structures. The turbulent flow is reproduced by the improved delayed detached-eddy simulation, a hybrid RANS-LES approach, and the two-phase volume of fluid method is applied to model the wave propagation. The governing equations are solved by a second-order accurate finite volume method. Computed turbulent flow field around the submerged breakwater is compared with the particle image velocimetry measurements obtained in the experimental flume. The computed result is in good agreement with the experimental measurements in terms of distinct vortical structures shed from the sharp edges of the obstacle and developed at the downstream junction. The numerical result further shows the three-dimensional behavior of the turbulent vortices and their breakdown into smaller structures.