针对矩形槽内导电流体普朗特数分别为 0.01、1、100 时,进行了流动形态和换热的数值模拟研究.数值结果表明:普朗特数对流动、温度分布影响不同,从而影响到对流换热的强弱,低普朗特数流体热浮升力作用大,流动以热驱动为主,换热强度弱,发现在低普朗特数下,数值模拟得出的努赛尔数并不能收敛到某一定值,而是在一个区间范围内"来回振荡";高普朗特数流体,电磁力作用大,流动以电磁力驱动对流作用,换热随着哈特曼数的增加而得到很大提高.
Following previous studies of rectangular cavity enclosures of aspect ratio 2, direct numerical two-dimensional simulations are conducted for the combined thermally and electromagnetically driven convection flow in three Prandtl number fluids of 0.01,1 and 100. It is found that possible physically realizable flows evolve, from a steady symmetric 2-cell flow at a lower-Prandtl number,while thermally driven flow prevails, to 4-cell flow at a high-Prandtl number, where the fluid is governed by Lorentz force. For high-Prandtl number fluid, the Nusselt number increases roughly as Hartmann number increases, while a slightly change of the Nusselt number for the lower Prandtl number fluid. The most striking finding in the comparisons of the convergence between high-Prandtl number fluid and lower Prandtl number fluid shows that the convergence of lower Prandtl number fluid could not be obtained.
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