Mixed convective flow past counter-rotating side-by-side cylinders at low Reynolds number

The present study focuses on the fluid flow and heat transfer characteristics around a pair of identical side-by-side circular cylinders placed in an unconfined medium. The cylinders are counter-rotating in a doublet like configuration. The top cylinder is rotating with a clockwise sense while the bottom one is rotating in a counter-clockwise sense. The investigation aims to explore the effect of mixed convective flows for various gap spacings 0.2, 0.7, 1.5, 3.0 between the cylinders at Richardson numbers 0, 0.25, 0.5, and 1. Computations are performed using a finite volume approach at various rotational speeds, keeping the Reynolds number based on the free stream flow at 100 with Prandtl number 0.71. In absence of rotation and thermal buoyancy, the flow is unsteady with vortex shedding behind the objects. The rotation brings stability to the flow, whereas the thermal buoyancy introduces instability. Additionally, the gap spacing offers geometrical interference effect. This complex interplay among the rotation, buoyancy and interference makes the fluid dynamics more intriguing. At a critical rotational speed, the instabilities are controlled resulting in the suppression of vortex shedding. However, the critical rotational speed strongly depends on the gap spacing and the strength of the buoyancy. As the gap spacing increases, the critical rotational speed increases. Similar behavior is also observed for increasing buoyancy. Based on the above analysis, a regime diagram is constructed to demarcate the unsteady and steady regions of operation.

Automated summary

The present study investigates the fluid flow and heat transfer characteristics around a pair of rotating circular cylinders in an unconfined medium. It is found that rotation stabilizes the flow, while thermal buoyancy introduces instability. The critical rotational speed strongly depends on the gap spacing and the strength of the buoyancy.