The Effect of Aspect Ratio of a Rectangular Cylinder inside a Lid-driven Square Enclosure on Mixed Convection

This study numerically investigated the two-dimensional mixed convection in a cold lid-driven enclosure with different aspect ratio of a hot rectangular cylinder. The Reynolds numbers were considered 100, 500 and 1,000, and the Grashof number and Prandtl number were fixed at 10 5 and 0.7, respectively. The aspect ratio was changed by 0.25, 0.50, 1.00, 2.00 and 4.00, as a main simulation parameter. The flow and thermal structures and the heat transfer characteristics were investigated in regard to the effects of variation in aspect ratio of cylinder in the present study, respectively. As a result, at the Reynolds number of 100 and 500, the average Nusselt number on the wall of the enclosure is the largest on AR = 4.00, while at the Reynolds number of 1,000, the average Nusselt number is the largest on AR = 0.25. Thus, the variation in aspect ratio has a remarkable influence on the heat transfer characteristics on mixed convection.