Numerical modeling of wave interaction with porous structures

This paper presents a numerical model for simulating wave interaction with porous structures. The model calculates the mean flow outside of porous str uctures based on the Reynolds averaged Navier-Stokes equations. The corresp onding turbulence field is modeled by an improved k-epsilon model. The flow in porous structures is described by the spatially averaged Navier-Stokes equations. The drag forces caused by the presence of a solid skeleton are m odeled by the empirical linear and nonlinear frictional forms. The numerica l model is first calibrated by simple experiments for flow passing through a porous dam with different porous media. Excellent agreements are obtained for the case using gravers with mean sizes of O(1 cm) to O(10 cm) as the m aterials for the porous dam. Reasonably good agreements are also obtained w hen small uniform glass bends with diameters of 3 mm are used. The calibrat ed numerical model is then employed to investigate the breaking wave overto pping a caisson breakwater, protected by a layer of armor units. Good agree ments between numerical results and laboratory data are obtained in terms o f both free surface displacement and overtopping rate. Different design sce narios are also studied numerically. The porous armor layer is effective in reducing the overtopping rate as well as in preventing the caisson breakwa ter from bottom scouring.