Flow structure around and heat transfer from cylinders modified from square to circular

This work aims at numerically investigating the influence of corner modification on the flow structure around and heat transfer from a square cylinder at a Reynolds number Re = 150 based on the cylinder width d and freestream velocity. The sharp corners of the square cylinder are rounded with r/d = 0 (square), 0.125, 0.25, 0.375, and 0.5 (circular), where r is the radius of the corner. The rounded corners have a profound effect on the flow structure from the perspective of flow separation, vortex strength, separation bubble, and wake bubble each playing a role in heat transfer from different surfaces of the cylinder. The boundary layer having a higher friction coefficient on the front and side surfaces leads to a higher local heat transfer. A shorter wake bubble renders a higher heat transfer from the rear surface. The increase in r/d from 0 to 0.5 leads to a 33% enhancement in the heat transfer from the cylinder. The enhancement largely results from a shrink in the wake bubble and an increase in vortex strength. The minimum time-mean drag and fluctuating forces are achieved at r/d = 0.25 and 0.125, respectively. The effect of r/d in various Reynolds averaged quantities is discussed.