Convection Patterns and Corresponding Critical Conditions in an Inclined Layer
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摘要: 通过二维流体力学基本方程的数值模拟,探讨了Prandtl(普朗特)数Pr=6.99时,倾斜矩形腔体中的对流斑图和斑图转换的临界条件.根据倾角θ和相对Rayleigh(瑞利)数Rar的变化,倾斜矩形腔体中的对流斑图可以分为:单滚动圈对流斑图、充满腔体的多滚动圈对流斑图和过渡阶段的多滚动圈对流斑图.当θ一定时,随着Rar的减小,系统由充满腔体的多滚动圈对流斑图过渡到单滚动圈对流斑图.这时,对流振幅A和Nusselt(努塞尔)数Nu随着Rar的增加而增加.当Rar=9时,随着θ的增加,系统由充满腔体的多滚动圈对流斑图过渡到单滚动圈对流斑图,这时对流振幅A随着θ的增加而减小,Nusselt数Nu随着θ的增加而增加.在θc-Rar平面上对多滚动圈到单滚动圈对流斑图过渡的模拟结果表明, 在Rar=2时, 腔体中没有发现多滚动圈对流斑图.在Rar为2.5左右时,腔体中出现多滚动圈到单滚动圈对流斑图的过渡.当多滚动圈到单滚动圈对流斑图过渡的临界倾角θc<10°时,θc随着Rar的减小而增加.当θc>10°时,θc随着Rar的增加而增加,在Rar≤5时,θc随着Rar的增加而迅速增加;当Rar>5时,θc随着Rar的增加而缓慢增加.θc与Rarθ的关系与Rar类似Abstract: Through numerical simulation of the basic equations for 2D fluid mechanics, the convection patterns and the critical conditions for pattern transition in an inclined rectangular cavity with Prandtl number Pr=6.99 were studied. According to the variations of inclination angle θ and relative Rayleigh number Rar, the convection patterns in the inclined layer can be divided into the convection single-roll pattern, the multi-roll pattern filling the cavity and the multi-roll pattern in the transitional stage. With constant inclination angle θ,the system transforms from the multi-roll pattern filling the cavity to the single-roll pattern with the decrease of relative Rayleigh number Rar, where the convection amplitude and Nusselt number Nu increase with Rar. For Rar=9,the system transforms from the multi-roll pattern filling the cavity to the single-roll pattern with the increase of inclination angle θ,where the convection amplitude decreases with θ,and the Nusselt number increases with θ.The simulation results of the transition from multi-roll to single-roll patterns in plane θc-Rar show that, for Rar=2,the multi-roll pattern is not found in the cavity. For Rar=2.5 or so, the transition from the multi-roll pattern to the single-roll pattern appears in the cavity. The critical θc value for the transition from the multi-roll to the single-roll patterns increases with the decrease of Rar for θc<10. The θc value increases with Rar for θc>10, where θc increases rapidly with Rar for Rar≤5,and increases slowly with Rar for Rar>5. The relation between θc and Rarθ is similar to θ.
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Key words:
- inclined layer /
- convection pattern /
- Rayleigh number /
- critical inclination angle /
- streamline
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