Nonlinear Wave, Composite Breakwater, and Seabed Dynamic Interaction

The nonlinear dynamic interaction among water waves, composite breakwater and a sand seabed of finite thickness is studied experimentally and numerically in this work. Laboratory experiments were conducted to record the water surface levels around the breakwater and the dynamic pore-water pressure inside its base and seabed foundation. Two numerical models have been adapted to simulate the problem; boundary-element and finite-element method (BEM-FEM) and poro-elastic FEM models. The BEM-FEM model couples the wave field and the porous media governed by the fully nonlinear potential and modified Navier-Stokes equations, respectively. The BEM-FEM model predicts the waves transmitted through the porous media to the onshore side. The poro-elastic FEM model uses Biot's equations and runs under the effect of the surface pressure computed by the BEM-FEM model. It also considers the caisson deformation and computes the dynamic stresses in the poro-elastic media. The dynamic pore-water pressures computed by the poro-elastic and BEM-FEM models have been compared with the experimental records. The BEM-FEM model has been revealed to predict accurately the wave field. Moreover, the dynamic response of a composite breakwater and its seabed foundation at different wave stages is discussed.