Experimental and numerical harmonic analysis of piston and sloshing mode gap resonance between fixed side-by-side barges under Stokes waves

Significant hydrodynamic interactions may occur between side-by-side operation structures at sea, posing a great threat to offshore structural integrity. This study investigates the resonance response of water in the narrow gap between two fixed identical barges using a two-dimensional numerical wave tank based on OpenFOAM and physical wave tank experiments. The effects of different gap widths on the amplification of free surface elevation at the center of the narrow gap and wave loads on the floating bodies are examined. The results reveal that the influence of gap width on these two factors is not the same. Harmonic analysis of wave height amplification and wave loads on the floating bodies shows that the effects of the second-order and third-order harmonic components differ. Finally, harmonic analysis of the wave height at different positions in the gap indicates that the phase difference in wave height across the gap originates from the natural frequency components generated by the nonlinear first-order sloshing mode. The beat pattern region is observed both before and after the first-order sloshing resonance, in which the beat frequency exhibits a typical V-shaped trend with the incident frequency.