Numerical investigation of coupled barge motions and wave-induced gap resonance

A numerical wave tank based on the fully nonlinear potential flow theory is built to study the incident wave-induced gap resonance between two freely floating barges. The boundary element method, in conjunction with the coupled auxiliary function approach, is employed to decouple body motions and hydrodynamic forces. The purpose is to analyze how the motions of the bodies affect the resonance (especially the resonance frequency) in the gap and, in turn, how the resonance affects the body motions. The study includes the piston mode in a narrow gap and higher sloshing modes in a wide gap. It is found that: (1) wave resonance in the gap does not occur at the natural frequencies associated with fixed bodies but happens at lower frequencies; (2) second-order resonance can be more easily triggered in a larger gap, and its effects can be more significant than first-order resonance; and (3) when wave resonance occurs, the resulting body motions show a clear dependence on the resonance patterns, especially the horizontal motions.