Flow-induced motion of a short circular cylinder spanning a rectangular channel

Flow-induced oscillation of an elastically supported circular cylinder subject to an incompressible fluid at Re = 100 and 400 has been studied using three-dimensional simulations. The cylinder is either subjected to a uniform flow in an unconfined surrounding or confined by rectangular channel, i.e. the cylinder is confined in both the span-wise and the cross-stream directions. The cylinder surface is represented by a virtual boundary method which replaces a solid object in flow by additional force distribution to satisfy local boundary condition. The simulations have been performed for nondamped cylinder with low mass ratio. For the unconfined cylinder, the effects of Reynolds number are studied. The effects of confinement have been investigated by varying the extent of the channel (and thereby also the cylinder length) in the span-wise direction. The maximal amplitude is found to be decreased by the confinement. For very strong confinement (short cylinder) the motion of the cylinder is governed by the natural frequency of the structure even beyond synchronisation range. The upper boundary of the synchronisation range exhibits no dependency on the confinement, only on Reynolds number.