Mixed Convective Flow Past Reverse Doublet like Rotating Side by Side Cylinders

The flow unsteadiness and the consequent evolution of the vortex shedding for flows around bluff objects are significantly important in fluid dynamics. Rotating the bluff objects may help in controlling such flow instabilities. Depending on the rotational speed, the unsteady flow may be transfigured into a steady pattern. On the other hand, multiple objects placed transverse to the incoming flow have destabilizing wake interactions. The instability even gets amplified with the introduction of thermal buoyancy. Under such conditions, the rotation plays an important role in stabilizing the wake dynamics. In view of the above, the present study aims to numerically investigate the wake and the thermal characteristics around a pair of circular cylinders arranged in side-by-side fashion in an unconfined medium. The top and the bottom cylinders are rotated in the counterclockwise and the clockwise directions, respectively, replicating a reverse doublet like configuration. The Reynolds and the Prandtl numbers are fixed at 100 and 0.71, respectively. The effect of the rotation on the flow instability is studied for Richardson number 0 to 1. The computations are performed using a finite volume method for the dimensionless cylinder spacings 0.7, 1.5, 3.0, and 5.0. The unsteady and the steady attributes are examined using the vorticity, isotherm-streamline contours, and lift signals. Finally, a regime diagram is constructed to exhibit the critical rotational speeds at which the flow becomes steady for various cylinder spacings.