Numerical simulations of unsteady natural convection in an enclosure with two hot circular parts at bottom

Three dimensional N-S equations were solved by control volume method to investigate the unsteady natural convection in an enclosure with two hot circular parts at the bottom. The enclosure is H high, 2H wide and 2H long with the diameter of the hot part D = 2H/3. The Rayleigh number varied from 10⁵ to 10⁶. The results indicate the average Nusselt numbers of the two hot parts tend to be constant as time increases Ra<;5×10⁵. When Ra ≥ 5×10⁵, average Nusselt numbers began to oscillate with time. The oscillation frequency and amplitude increase with Rayleigh number increasing.