Structural permeability effects on the interaction of a solitary wave and a submerged breakwater

The unsteady two-dimensional Navier-Stokes equations and Navier-Stokes type model equations for porous flows were solved numerically to simulate the interaction between a solitary wave and a submerged porous breakwater. The free surface boundary conditions and the interfacial boundary conditions between the water and the porous media are in complete form. A piston-type wavemaker, set-up in the computational domain, generated the incident solitary wave. The accuracy of the numerical model was verified by comparing the numerical results with the experimental data. Having verified the accuracy of the numerical model, the effects of several parameters on the interaction of a solitary wave and a submerged breakwater were systematically investigated. These parameters include the incident wave height, the aspect ratio of the breakwater, and the porosity including the impermeable case. The flow fields near the breakwater are discussed in terms of the velocity vectors, the vortex shedding and the trajectories of the fluid particles. The pressure drag acting on the breakwater was also calculated. The numerical results reveal that if the breakwater width is small compared with the effective wave length, the structure permeability has no apparent effect on wave transformation. For wide porous breakwaters, if the structure porosity is small, the increase in the porosity results in the reduction of the transmission coefficient; otherwise the transmission coefficient increases with porosity.