Abstract
Fluid resonance within a narrow gap between two boxes in close proximity is investigated based on the open-source CFD package, OpenFOAM. The upstream box keeps fixed but with varying breadths, the downstream box heaves freely under wave actions and has a constant breadth. For comparison, a two-stationary box system is also considered. The aims of this work are to study the effects of the breadth ratio of the two boxes, i.e., the ratio of the breadth of the upstream box to that of the downstream box, on the hydrodynamics of the resonant fluid inside the gap and the motion of the downstream box. It has been found that the amplification of resonant wave height in the gap decreases significantly with the increase of the breadth ratio and the incident wave height, while the fluid resonant frequency seems insensitive to the breadth ratio. Compared with the two-stationary case, the fluid resonant frequency for the two-box system with the downstream box heaving freely shifts towards higher values. Furthermore, for the cases with a smaller incident wave height or a larger breadth ratio, there usually exists a local peak in the curve of the heave displacement versus the incident wave frequency. A larger breadth ratio leads to a smaller heave motion of the downstream box.
