封闭方腔自然对流的涡结构和传热特性

为研究封闭方腔自然对流的涡结构和传热特性，对普朗特数，Pr=0.71，方腔高长比A=H/L=1，瑞利数Ra=1.58×109的二维封闭方腔自然对流进行了直接数值模拟. 给出了水平边界层发展阶段和垂直边界层转捩阶段的流场结构以及Nu数分布. 结果表明，压力梯度对方腔的水平速度变化起着决定性的作用；高Ra数下的自然对流在逆压梯度作用下水平方向形成一系列的涡，这些涡使得水平边界层流动形成分层结构；壁面Nu数与速度梯度?v/?y有着密不可分的关系. 

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.