Suppression or Agitation of Vortex-induced Vibration (VIV) of a Cylinder in the Presence of Thermal Buoyancy at Low Reynolds number

We numerically study the effect of thermal buoyancy (acting transverse to the flow) on transverse VIV of an elastically mounted cylinder with the surface, heated to a prescribed temperature. An in-house solver based on sharp interface immersed boundary method is employed (Garg et al., Phys. Fluids., 2018). The numerical simulations are performed for the following parameters: Re = 50, Prandtl number, Pr = 7.1, mass ratio, m = 2, reduced velocity, U_R = [4-10], and Richardson number, Ri = [0-4]. At lower Ri, the thermal buoyancy suppresses the vortex shedding and consequently, the maximum amplitude of the cylinder. By contrast, a larger value of Ri shows galloping. Therefore, a critical Ri exists for the transition from the suppression to galloping. For larger (lower) Ri, the variation in the instantaneous pressure force at the cylinder surface over a time cycle is significant enough (constant) to agitate (suppress) the VIV. The vibration frequency remains nearly same for all values of U_R for larger Ri, and influence of added mass is observed. These findings could help to design VIV systems in the presence of the thermal buoyancy for energy-harvesting applications.