Numerical study of solitary wave interaction with porous breakwaters

Solitary wave interaction with porous breakwaters is studied by using a two-dimensional numerical model. In this model, flows outside of porous media are described by Reynolds-averaged Navier-Stokes equations. For porous flows, the spatially averaged Navier-Stokes equations, in which the effect of porous media is considered by including additional inertia and drag forces, are derived and implemented. The drag force is modeled according to Morison's equation assuming uniform spherical particles within porous media. The corresponding drag force coefficient is expressed as the function of Reynolds number and hence the proposed porous flow model is valid in a wide range of porous flow regimes, i.e., laminar (linear friction), transitional, and turbulent (nonlinear friction) flows. The numerical model is validated against available theories and experimental data for both long wave and solitary wave interaction with porous breakwaters. The model is then employed to study solitary wave interaction with fully emerged rectangular porous breakwaters with different length and particle size. Based on the results, the characteristics of wave reflection, transmission and energy dissipation are discussed. Additional numerical tests are conducted to study the effects of depth of submergence and porosity of breakwaters on wave transformation. The scale effects in small scale and large scale model tests are also discussed by performing numerical experiments in the reduced and enlarged numerical wave flumes.