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.