Wave-current interaction effect on gap resonance between two side-by-side barges

Ship-to-ship (STS) bunkering of liquid fuel, e.g., LNG, has emerged as a more practical way to ensure high bunkering volumes and good access without regional restrictions and upgrading of existing infrastructures at the port. Wave resonance in the narrow gap between side-by-side receiving vessel and bunkering vessel happens when the wave frequency is close to the natural frequency of the gap flow. Large wave elevation in the gap and hydrodynamic forces on the
ships are expected, thus reducing the time window of the bunkering operation and even risking the safety of the crew. It is well known that the wave frequency and amplitude can be affected by the presence of current. Correspondingly, the waves and loads on marine structures will be somewhat different from the scenario without current, which will have significant influence on the bunkering operation. However, few previous studies have reported in the literature for wave resonance considering current effect. In the present work, the finite-amplitude fluid resonance inside the gap between two ship cross-sections in side-by-side configuration is studied under combined waves and currents. Both a uniform current and a shear current with constant vorticity are considered. A fully nonlinear numerical wave tank is established based on the commercial CFD package STAR-CCM+. The unsteady Reynolds averaged Navier-Stokes turbulence model is applied to consider viscous dissipation. The volume of fluid method is applied to capture the free surface, and the flow field analytically obtained from the stream function method is specified in the forcing zones at upstream and downstream boundaries, respectively, by the user-defined wave elevation and velocity. The influence of following current on the wave amplitude in the gap and hydrodynamic load on the cross-sections is investigated by comparison with the cases without current. The relation between the wave or force amplitude and the vorticity of the shear is further analysed. The present study may provide useful results about gap resonance and hydrodynamic loads on two approaching marine structures during the bunkering operation in wave-current environment.