Vortex structure and convective heat transfer of natural convection in a closed square cavity

For studying the vortex structure and convective heat transfer in a closed square cavity filled by air, a direct numerical simulation study of the natural convection was conducted at the parameters of Prandtl number Pr=0.71, aspect ratio A=H/L=1, Rayleigh number Ra=1.58×10⁹. The fluid structures and the Nusselt number distributions of the horizontal boundary development stage and the vertical boundary layer transition stage were presented. These results suggest that the pressure gradient plays a decisive role for the horizontal velocity variation; a series of vortexes are formed as a result of the adverse pressure gradient and these vortexes make the stratification of the horizontal flow; the wall Nusselt number has a closed relationship with the velocity gradient ∂v/∂y.