Investigations on gap resonance occurring in between a fixed body and a vertical quay mounted on permeable seabeds

A two-dimensional (2D) viscous flow numerical wave flume based on OpenFOAM is established to investigate the gap resonance occurring in between a fixed body (box) and a vertical quay mounted on permeable seabeds with varying slopes. Capabilities of the numerical model in reproducing the fluid transfer within permeable media and the gap resonance phenomenon are verified using existing experimental data separately. Subsequently, the effects of both the topographical slope and porosity on the following three aspects of hydrodynamic features of gap resonance are comprehensively studied: (i) the resonance characteristics of the fluid inside the gap, (ii) the reflection, transmission and energy loss coefficients, and (iii) the wave forces exerting on the body. It is found that the resonant wave height within the gap gradually declines as the porosity rises. Under gap resonance conditions, the trends of the reflection coefficient and the energy loss coefficient with respect to both the slope and the porosity are completely opposite to each other. The impacts of the porosity on the maximum horizontal wave force amplitude depend on the slope. The vertical wave force amplitude under gap resonance conditions shows an upward and a decline tendency with the slope and the porosity, respectively.