Seiches and harbour oscillations in a porous semi-closed basin

Abstract In this paper, we investigate the propagation of long waves in to a harbour with three different porous bottom configurations. The governing shallow water equations are modified to include additional terms to model the porous region. Analytical solutions are sought in the non-porous bottom case using a separation of variables method to provide the natural resonant periods of the basin for the three different harbour geometries. For fixed basin length the lowest resonant frequency increases as the profile goes from rectangular to parabolic to triangular. However, the rate of amplification increases from triangular, rectangular to parabolic. A computational scheme is proposed, using a finite volume method on a staggered grid, and is validated against the analytical solution prior to being used to investigate the effect of porosity and friction on wave resonance. The relative effectiveness of friction and porosity in controlling resonance is found to be dependent on basin geometry.