Fluid resonance in the narrow gap of a box-wall system under cnoidal wave action

Abstract

Fluid resonance within a narrow gap formed by a box in close proximity to a plane wall under cnoidal wave action is investigated using the Computational Fluid Dynamics (CFD) package OpenFOAM®. Fluid resonance behavior excited by the second-order harmonic component of the incident cnoidal waves is concerned. Numerical simulations show the large second-order induced wave height in the gap which increases as the incident wave height gets larger or the water depth gets shallower. The large double-frequency component of the cnodial waves is the major reason for the phenomenon. Harmonic analysis indicates that the CFD results can be represented well by a second-order approximation, and the free surface nonlinearity is an indispensable factor in the action of the cnoidal incident wave. Similar phenomenon is also found in the horizontal wave force. However, the second-order induced resonance within the gap has insignificant effect on the vertical wave force.