Model-dependent gap resonance investigation with Kelvin–Helmholtz instability in floating channels

This study investigates gap resonance in a floating channel system with emphasis on the role of flow modeling in capturing shear-layer instability and resonance excitation. Resonance frequencies identified by using potential flow theory and subsequently examined through computational fluid dynamics simulations based on both laminar and Reynolds-averaged Navier–Stokes (RANS) models. The results reveal a systematic difference between laminar and RANS models to predict Kelvin–Helmholtz-type shear-layer instability induced by flow separation at the sharp edges. Although both models capture the separation–recirculation–reattachment process, the RANS model predicts a stronger and more coherent recirculation zone due to the inclusion of turbulent viscosity, leading to enhanced momentum exchange and resonance intensity. In addition, a resonance-side shift is newly identified, in which the dominant resonance location shifts between the incident and opposite sides as the channel wall draft varies, reflecting changes in energy penetration and diffraction pathways under viscous flow conditions.