Three-dimensional analysis of critical Rayleigh number for natural convection in a rectangular enclosure

Numerical analysis has been carried out to investigate the behavior of 3D natural convection in a differentially heated rectangular enclosure with 8 height/width aspect ratio. Parameter study as a function of Rayleigh number has been performed to determine the critical Rayleigh number, which marks the transition from steady flows to time-periodic flows. As a result, it is revealed that 3D critical Rayleigh number is evaluated 4.0×10^5≤Ra_c<6.0×10^5,which is higher than 2D critical Rayleigh number 2.9×10^5. The results indicate that 3D flows become more stable than 2D ones.