The galloping of a 4:1 rectangular cylinder at Re=300

The flow-induced vibration (FIV) of a rectangular cylinder with a side ratio of 4 at Re = 300 is numerically investigated by a two-dimensional spectral-element method. The cylinder is constrained to vibrate only in the cross-flow direction. The effects of mass ratio and damping ratio are studied. Boss typical FIV, vortex-induced vibration (VIV), and galloping were found. Although the quasi-steady theory predicts that galloping will not occur for a 4:1 rectangular cylinder, we still find galloping in the mass ratio range of 6 < m* < 28. VIV is dominant at low, reduced velocities; however, galloping is found after a certain value. Galloping may be caused by the trailing edge vortex. In the case of low mass ratios, VIV will suppress galloping. It was found that, within a certain range of reduced velocity and mass ratio, the increase in damping will weaken vortex induced vibration, thus causing galloping to reappear.