Experimental investigation of flow-induced vibration interference between two circular cylinders

This paper presents experimental results concerning flow-induced oscillations of circular cylinders arranged in tandem. New measurements on the dynamic response oscillations of an isolated cylinder and flow interference of two cylinders are shown. Preliminary flow visualization employing a PIV system is also shown. The models are mounted on an elastic base fitted with flexor blades and instrumented with strain gauges. The base is fixed on the test-section of a water channel facility. The flexor blades possess a low-damping characteristic (zeta similar or equal to 0.008-0.0109) and they are free to oscillate only in the cross-flow direction. The Reynolds number of the experiments is from 3000 to 13 000, and reduced velocities, based on natural frequency in still water, vary up to 12. The interference phenomenon on VIV is investigated by conducting experiments in which the upstream cylinder is maintained fixed and the downstream one is mounted on the elastic base. The results for an isolated cylinder are in accordance with other measurements found in the literature for m* similar or equal to 2 and 8. For the tandem arrangement and m* similar or equal to 2, the trailing cylinder oscillation presents what previous researchers have termed interference galloping behaviour for a centre-to-centre gap spacing ranging from 2D to 5.6D. These initial results validate the experimental set-up and lead the way for future work, including tandem, staggered and side-by-side arrangements with the two cylinders free to move. (c) 2006 Elsevier Ltd. All rights reserved.