Effect of Active and Passive Flow Control on the Fluid Flow and Thermal Characteristics past Rectangular Cylinders of Different Aspect Ratios: A Numerical Study

The present study investigates fluid flow and heat transfer characteristics past rectangular cylinders of various aspect ratios with active (suction or blowing applied at filleted sharp corners) and passive (sharp corners with fillet) flow control techniques for low Reynolds numbers. The equations governing fluid flow and heat transfer are solved using an in-house solver based on the Streamline Upwind/Petrov-Galerkin finite element algorithm in Cartesian coordinates. The results are validated against literature data, and parametric studies were conducted for fluid flow past rectangular cylinders of different aspect ratios (1, 3, and 5) at a Reynolds number of 150, with non-dimensional fillet radius varying from 0.0 to 0.5. Suction or blowing velocities of 5%, 12%, and 20% of the inlet velocity are applied at fillets. Results demonstrate that integrating active and passive flow control reduces drag by 19.5% for rectangular cylinders with an aspect ratio of 3 and 35% for rectangular cylinders with an aspect ratio of 5, which may be attributed to the varying pressure distribution across the cylinder surface. The temperature contour indicates an even temperature distribution, thereby mitigating the formation of thermal hot spots. Thermal performance factor analysis reveals that the rectangular cylinder with an aspect ratio of 5 and a non-dimensional fillet radius of 0.5 exhibits significantly enhanced heat transfer performance when flow control strategies are implemented, outperforming the baseline configuration while incurring acceptable pressure penalties.