Experimental investigation on vortex-induced vibration and galloping of rectangular cylinders of varying side ratios with a downstream square plate

Abstract

A rectangular cylinder in a fluid flow is known to show complicated cross-flow vibration behavior due to the interaction between the Kármán vortex-induced vibration and galloping. Wind tunnel experiments were carried out to investigate the cross-flow vibration behavior of several rectangular cylinders for which different stream-wise lengths, B and a fixed cross-flow height, D were used to define the side ratio, B/D of 1.0, 1.2, 1.4, and 1.6. For the isolated cylinder, stronger interaction between KVIV and galloping was demonstrated as the B/D was increased. The placement of a downstream square plate at a gap, S from the cylinder had a significant effect on the peak of VIV, AVIV of the cylinder. With the downstream square plate at S/D ?= ?1.17, the AVIV was enhanced about five times than that of the isolated cylinder (B/D ?= ?1.0). In contrast, the AVIV was suppressed by about 50% for two cylinders, B/D ?= ?1.2 and 1.6, with S/D ?= ?1.15 and 2.12, respectively. However, galloping was significantly enhanced for two cylinders, B/D ?= ?1.2 and 1.4 with S/D ?= ?1.15. These findings are useful to develop a vibration control technique crucial to avoid hazardous vibrations or to induce vibrations for beneficial purposes.