Simulation of Combined Thermal Mixed Convection and Radiation in a Discretely Heated Lid-Driven Cavity using a Lattice Boltzmann Method

In this work, we examined numerically the heat transfer by mixed convection coupled with surface thermal radiation in a square cavity with a moving wall, using the Lattice Boltzmann method. The cavity is discretely heated from its left and lower walls with a hot temperature and cooled from its right wall, while the upper wall is adiabatic and moves from left to right at a constant velocity. The cooling medium is assumed to be air, which modeled as a radiatively transparent medium. The critical parameters in this study are the emissivity of the surfaces, ε, which varies between 0 and 1, and the number of Richardson, Ri, which varies from 0.1 to 10. The latter varies by varying the Reynolds number, Re, with a Rayleigh number, Ra = 105. The results obtained indicate that the dynamic structure is monocellular, which illustrated by the existence of a large cell generated by the combined effects of shear and buoyancy. In addition, it should be noted that the increase of the emissivity of the surfaces enhances the radiative heat exchange, reduces convective effect and improves the total heat exchange. Additionally, it is discovered that an increase in Ri causes a significant decrease in convective and global heat exchange, while just slight increase in radiative heat transfer.