Vortex-Shedding Suppression in Mixed Convective Flow past a Heated Square Cylinder

The present study investigates numerically the phenomenon of vortex-shedding and its suppression in twodimensional mixed convective flow past a square cylinder under the joint influence of buoyancy and free-stream orientation with respect to gravity. The numerical experiments have been conducted at a fixed Reynolds number (Re) of 100 and Prandtl number (Pr) of 0.71, while Richardson number (Ri) is varied from 0 to 1.6 and freestream orientation, α, is kept in the range 0≤ α ≤ 90, with 0 corresponding to an upward flow and 90 representing a cross-flow scenario, respectively. The continuity, momentum and energy equations, subject to Boussinesq approximation, are discretized using a finite difference method and are solved by a semi-explicit pressure correction scheme. The critical Richardson number, leading to the suppression of the vortex-shedding (Ric), is estimated by using Stuart-Landau theory at various free-stream orientations and the neutral curve is obtained in the Ri-α plane. The neutral curve exhibits an interesting non-monotonic behavior with Ric first increasing with increasing values of α upto 45 and then decreasing till 70. Beyond 70, the neutral curve again exhibits a sharp increasing asymptotic trend with Ric approaching very large values as α approaches 90. The suppression of vortex shedding is not observed at α = 90 (cross-flow). In the unsteady flow regime, the Strouhal number (St) increases with the increase in Richardson number. Keywords—bluff body, buoyancy, free-stream orientation, vortex-shedding.