In this work, we present a two-dimensional study of natural convection in a square air-filled cavity whose two vertical sides are subjected to a temperature difference, while the other two horizontal ones are adiabatic. The numerical method used is that of finite elements used in the COMSOL calculation code. We first studied pure natural convection, by varying the Rayleigh number from to , then its coupling with surface radiation, by varying the emissivity of the cavity surfaces from 0 to 0.6. The results are presented in the form of isotherms, pressure, current etc. It appears from this study that for a Rayleigh number less than 100, the fluid presents a vertical thermal stratification due to heat transfer only by conduction which does not generate any convective flow. The presence of surface radiation does not modify the equations governing fluid movements but only alternates the thermal boundary conditions. The coupling of natural convection and surface radiation occurs only through thermal boundary conditions. The variation in the emissivity of the walls does not influence the temperature isotherms.

Natural convection, square cavity, convection-radiation coupling, numerical simulation