Thermal buoyancy induced suppression of wake-induced vibration

We numerically investigate the effect of thermal buoyancy on wake-induced vibration (WIV) of an elastically mounted square prism in the wake of an identical stationary prism. The upstream prism is heated at a prescribed temperature while the downstream prism is insulated and vibrates transversely to the flow direction. The Reynolds number, based on side of the prism is, Re = 100 and center-to-center distance is twice the side of the prism. Numerical simulations were performed for mass ratio m = 3, Prandtl number Pr = 7.1 and Richardson number Ri = [0, 1]. The reduced velocity U-R is varied in a range from 4 to 30. The maximum oscillation amplitude occurs at U-R = 5 at Ri = 1 as compared to Ri = 0. We report 50% reduction in the amplitude at Ri = 1 as compared to Ri = 0, implying WIV suppression due to the presence of thermal buoyancy. A complete suppression occurs at U-R > 7 at Ri = 1. The lock-in (synchronization) region is narrow for both the cases. The downstream prism oscillates in phase to the lift force at Ri = 1 as phi remains 0 degrees, whereas at Ri = 0, phi changes abruptly from 0 degrees to 180 degrees and remains 180 degrees for higher U-R. We briefly discuss the influence of thermal buoyancy on wake dynamics. The present results provide insights to suppress the WIV by tailoring the thermal buoyancy for multiple bluff bodies in laminar flow.