侧向加热腔体中的多圈型对流斑图

基于流体力学方程组的数值模拟,研究了倾角θ=90°时侧向加热的大高宽比腔体中的对流斑图.对于Prandtl数Pr=6.99的流体,在相对Rayleigh数2≤Ra r≤25的范围内,腔体中发生的是单圈型对流斑图.对于Pr=0.0272的流体,取Ra r=13.9,随着计算时间的发展,腔体中由最初的单圈型对流斑图过渡到多圈型对流斑图,这是出现在侧向加热大高宽比腔体中的新型对流斑图.对不同Ra r情况的计算结果表明,Ra r对对流斑图的形成存在明显的影响.当Ra r≤4.4时是单圈型对流滚动;当Ra r=8.9~11.1时是过渡状态;当Ra r≥13.9时是多圈型对流滚动.对流最大振幅和Nusselt数Nu随着相对Rayleigh数的增加而增加.该对流斑图与Pr=6.99时对流斑图的比较说明,对流斑图的形成依赖于Prandtl数.

Multi-Roll Type Convection Patterns in Cavities Heated Laterally

The numerical simulation was carried out based on the hydrodynamic equations,and the convection patterns in cavities with large aspect ratios heated laterally at inclined angleθ=90°were studied.For the fluid with Prandtl number Pr=6.99 in the range of reduced Rayleigh number 2≤Ra r≤25,a single-roll type convection pattern occurs in the cavity.For the fluid with Pr=0.0272 and Ra r=13.9,with the development of calculation time,the convection pattern in the cavity transforms from the original single-roll type to the multi-roll type,which is a new type of convection pattern pertinent to large-aspect-ratio cavities heated laterally.The calculation results for different Ra r values show that,Ra r has a significant effect on the formation of convection patterns.A single-roll type convection pattern occurs for Ra r≤4.4;for Ra r=8.9~11.1,the system is in a transitional state;and a multi-roll type convection pattern appears for Ra r≥13.9.The maximum convection amplitude and Nusselt number Nu increase with Ra r.The comparison with the convection pattern for Pr=6.99 shows that the formation of the convection pattern depends on Pr.