Analysis of wave resonance in gap between two heaving barges

•Approach for resonance frequencies of narrow-gap liquid is introduced.•Fully-nonlinear numerical wave tank is developed to verify this approach.•Wave resonances in gap between two heaving barges are analyzed.•Effects of gap width, draft and relative size of barges on gap resonance are discussed.

A numerical wave tank based on the fully-nonlinear potential-flow theory is built to simulate water wave radiations by floating barges. An approach from the free sloshing model is proposed to predict dominant resonance frequencies of the liquid motion in the gap between two barges. The effectivity of this approach is verified through the ‘response amplitude operator’ (RAO) analysis. Then, the approach is applied to investigate wave resonances of the gap liquid. In the first series of case studies, two identical barges are considered. Effects of the barge distance and draft on the gap resonance are investigated. It is found that, as the gap distance grows from narrow to wide, the dominant resonance may transfer from the piston type to the sloshing type. As the barge draft decreases, this transfer would emerge earlier. The second series of case studies concern two different barges in a close proximity. It is found that the relative breadth of two barges has minor effects on the resonance frequency, but affects RAOs at resonance evidently. The relative barge draft has a strong effect on resonance frequencies.