Effect of the slope gradient of submerged breakwaters on wave energy dissipation

Abstract

This paper presents the results of studies on the effects of the slope gradient of a fully permeable submerged breakwater. A newly developed numerical model is used, which is able to consider the flow through a porous medium with inertial, linear and nonlinear resistance terms. The model is therefore able to directly simulate the interaction between the wave-structure and the sand-seabed for a submerged breakwater. The model can also determine the eddy viscosity with the LES turbulence model in a 2-dimensional wave field. The developed model was validated by comparison with existing experimental data for wave deformations caused by the rectangular permeable submerged breakwater. It was later used for various numerical experiments which investigated the complicated hydrodynamics associated with the varying slope gradient of a permeable submerged breakwater. Numerical results revealed that the reflection and transmission coefficients decrease simultaneously with a decrease in slope gradient and the wave breaking over the crown of the submerged breakwater tends to move towards the offshore side with the steep slope gradient of the breakwater. In addition, clockwise circulation flow is generated behind the submerged breakwater, and its magnitude increases with the slope of the structure.