Numerical Analysis of Narrow Gap Resonance in Twin-Box Floating Body System

The resonant response of waves within the narrow gap of a twin-box floating body system, known as gap resonance, is a hydrodynamic phenomenon with significant engineering applications. When coupled with body motions, the system dynamics become highly complex, involving the interplay of body motions, fluid resonance, and damping mechanisms that govern the response amplitude. In this study, a validated two-dimensional viscous numerical wave tank was established to investigate the hydrodynamics of narrow gap resonance under three constraint modes: double-fixed, front-fixed, and rear-fixed. To quantify the system’s response, the following key parameters were recorded and analyzed: the wave height in front of the weather-side box, the resonant wave height within the gap, the transmitted wave height, and wave forces exerted on the floating bodies. To provide mechanistic insight, velocity contours, free surface profiles, and spectrum diagrams were examined for representative conditions. By comparing narrow gap resonance characteristics across various degrees of freedom and configuration layouts, this study elucidates the distinct impacts of the position effects of the weather-side and leeward-side floating bodies, as well as the influence of degree-of-freedom coupling on resonance responses. Furthermore, the intensity of nonlinear effects and the energy transfer mechanisms associated with each mode were also evaluated.