Application of Dipole Damper Panels in Modelling Gap Resonance

Abstract

Modelling the fluid response in a gap using conventional frequency domain potential flow solvers is a challenge due to its resonance behavior and the importance of viscous effects. Damping panels, or lids, are usually used to represent the main viscous effects, when more direct method of calculation is not applicable due to limitations on time or computation resources. Although, it is known that the main contributor to the damping is the flow separation at the gap inlet, these methods usually relate the magnitude of the effective damping to the vertical fluid velocity at the surface. In the present study, the application of dipole damping surfaces, as introduced in potential flow code WAMIT, is studied for modelling the flow separation effects more consistently. The relative fluid velocity at the inlet is used to model the damping effect of flow separation. Simplified empirical models are proposed to estimate the magnitude of the damping. The experimental study of flow between two side by side barges by Molin et a. 2009 [1] has been selected to evaluate the present modelling approach. The numerical results show good agreement with the measurements while providing a more consistent basis to apply stochastic linearization of the quadratic damping due to flow separation at the gap inlet.