Thermal buoyancy effects on the flow field and heat transfer of a rotating cylinder: A numerical study

Abstract

The present paper numerically investigates the laminar, two-dimensional and horizontal flow around a horizontal isothermal rotating cylinder under the buoyancy effect. To study the buoyancy effect, a range of Grashof numbers from 0 to 12 × 104 is used, and to check the effect of the cylinder rotation, the ratio of the rotational speed to the free-stream velocity between −4.5 and 4.5 is applied. The simulation is carried out at the Reynolds number of 200 and the Prandtl number of 0.7. To simulate the fluid flow, the Navier-Stokes equations are numerically solved using a finite-volume scheme. Results show that the interaction of the main stream with the rotation and buoyancy can alter the flow field and heat transfer characteristics such as flow pattern, surface pressure distribution, lift and drag coefficients, and Nusselt number. The clockwise (cw) rotation decreases the amplitude of oscillations in the flow compared to the counterclockwise (ccw) rotation. In ccw rotation, as the Grashof number increases, the mean lift coefficient increases; while in cw rotation, increase in the Grashof number reduces the mean lift coefficient. Moreover, in terms of Grashof numbers ranging between 8 × 104 and 12 × 104, the Nusselt number is almost unchanged.