Numerical study of wave interaction with a composite breakwater located on permeable bed

Abstract

The response of a composite breakwater against wave load is numerically investigated using Smoothed Particle Hydrodynamic (SPH) model. Permeability of the stone layer beneath the caisson is implemented in the model and a new scheme free of any tuning parameter is introduced to estimate the dynamic friction forces transitionally applied to the moving caisson. To overcome pressure noises inside the porous medium, a treatment based on δ-SPH scheme is utilized and its performance is verified by modeling a simple hydrostatic condition inside a homogeneous porous medium. The model ability in simulating fluid flow through porous media is approved by modeling dam break flow through a porous block. In addition, a caisson breakwater with an impermeable bed is modeled and the results are compared with experimental and other numerical results to validate the performance of the introduced friction coefficient. Then, the same caisson but with a permeable bed is simulated against the incident waves and the horizontal forces as well as sliding displacements are calculated. Good agreements with the experimental data show the acceptable performance of the developed model as well as the importance level of the permeable bed on the caisson response. Based on the results, neglecting the flow through the porous bed of the caisson may result in an overestimated wave force and an underestimated caisson sliding. Finally, the caisson responses to different wave conditions are studied and it is shown that the peak load on the caisson increases as the wave height or wave period rises.