Aided Mixed Convection past a Heated Square Cylinder at Low Blockage Ratio

This paper investigates numerically the flow and heat transfer in air (Pr=0.71) by mixed convection past a heated square cylinder under aiding buoyancy effect in a confined channel. The numerical simulations are performed in the range of parameters 20≤Re≤45 and 1.61x103≤Gr≤6.33x103 for a fixed blockage ratio D/L of 0.1. The combination in the present study of these two Re and Gr parameters is reduced so that the Richarson number varies from 0,8 to 8, in order to neglect neither free convection (Ri<0.1) nor forced convection (Ri>10). The steady two-dimensional governing equations are solved by the finite volume formulation using the open source OpenFoam® code. The representative flow structure, isotherm patterns and local Nusselt number evolution are presented and discussed. The effect of both the Reynolds number and the buoyancy parameter on the fluid flow and the heat transfer are also analyzed. It is found that the wake region size strongly depends on both Reynolds and Grashof numbers and this region is shown to increase in size increasing the Reynolds number and/or decreasing the Grashof number. Moreover, increasing the Reynolds number leads to a heat transfer enhancement more pronounced on the front face of the obstacle, whereas increasing the Grashof number leads to a heat transfer enhancement more pronounced on the side faces.