Flow-induced vibration of two elastically mounted tandem cylinders in cross-flow at subcritical Reynolds numbers

A series of experimental studies on flow-induced vibration (FIV) of two identical elastically mounted circular cylinders in tandem arrangement were carried out in a low turbulence surface water channel. The Reynolds number was between 2.86 x 10(4)-1.14 x 10(5). Both upstream and downstream cylinders with diameter of 8.89 cm and mass ratio of 1.343 were allowed to oscillate in the transverse direction. Four spacing ratios T/D = 1.57, 2.57, 3.57 and 4.57 (where T is the center-to-center spacing and D is the cylinder diameter) were selected. Two virtual spring-damping oscillators were used to conduct the tests and measure the position signals of two tandem circular cylinders undergoing FIV. The vibrations and fluid forces of the cylinders were analyzed and discussed to illustrate the mechanisms of interaction between the two cylinders. The experimental results indicate that the Fly characteristics of the upstream cylinder are similar to those of a single cylinder for T/D = 2.57, 3.57 and 4.57 when the reduced velocity does not exceed 12.0. Moreover, the FIV response of the upstream cylinder in the two tandem cylinder system with T/D = 1.57 is significantly different from that of the isolated cylinder. The vibration of and the fluid force on the downstream cylinder are obviously influenced by the upstream cylinder for the spacing range tested. Vortex-induced vibration (VIV)-like response features are observed for the downstream cylinder.