An Experimental Study of the Cross-Flow on a Pair of Staggered Cylinders Subject to Forced Oscillations

The study of the flow around a small group of circular cylinders has attracted considerable interest in recent years due to the importance of this type of flow for a better understanding of both bluff-body fluid dynamics and fluid structure interaction. The problem of two staggered stationary cylinders has been addressed by a number of authors. Significant changes in the fluid dynamics occur when the structure is allowed to oscillate naturally or is forced to oscillate. The problem of the cross-flow on an oscillating cylinder has also been studied by several authors. Less studied is a combination of the two problems whereby one or more cylinders can be forced to oscillate. This work presents an experimental investigation of the fluid dynamics around a pair of similar circular cylinders subjected to forced harmonic motion. The present study consists in determining the frequency content in the wake of the cylinders from hot film measurements. Results have shown the occurrence of lock-in not only at the forced frequency but also at sub and super harmonics.