Vortex induced vibration of a circular cylinder with a filament by using penalty immersed boundary method

Abstract In this paper, vortex induced vibration of a circular cylinder with an attached filament is numerically studied by a Penalty Immersed boundary method (PIBM). In the current work, we study the effects of a single filament on the flow wake of a fixed cylinder, as well as its dynamic response when it is free to move transversely. Two key parameters, the bending coefficient (Kb) and the length (L) of the filament are considered. We report that for a static cylinder, by increasing the length or the rigidity of the filament, both the mean drag force and the fluctuation amplitude of the lift force on the cylinder can be reduced. When the cylinder is free to move, it is found that the existence of a filament actually enhances the vibration of the cylinder by comparing to that of a bare cylinder, differentiating from the prediction of lift fluctuation on a fixed cylinder. In the meanwhile, it leads to a broader resonance region on the vibration response of the cylinder with respect to the reduced velocity. Moreover, various flow patterns are identified in the wake of cylinder for different filament lengths.