Influence of a Neighboring Counterpart on the Vortex-Induced Oscillation of a Circular Cylinder

Abstract

The flow pattern around a pair of two parallel circular cylinders whose axes are on a plane perpendicular to a uniform flow is known to vary drastically with the gap between them. In this work, one of the cylinders is elastically supported in a wind tunnel to allow motion normal to the flow and its axis, while the other is fixed rigidly. The effects of the gap on the resonance oscillation of the elastically supported cylinder with the karman vortex shedding is investigated. The results are summarized as follows. (1) The resonance amplitude decreases with the proximity of the fixed cylinder when the ratio of the gap to the cylinder diameter s/d is in the range 3∼0.5, and slightly recovers when s/d<0.5. (2) The depression of the resonance amplitude at a large gap is attributed to the reductions of the periodicity and the two-dimensionality of the vortex shedding due to the neighboring fixed cylinder, and the recovery at a smaller gap is due to the establishment of the flow regime with the double scale vortex. (3) When s/d=0.125, the jet flow through the gap attaches alternately to the cylinders, which makes the oscillating behavior intermittent.