竖直平板嵌入非Darcy多孔介质时,数值研究流过平板的不稳定MHD自然对流中的Dufour和Soret效应

就竖直平板嵌入非Darcy多孔介质中,导电流体流过平板时作不稳定的二维磁流体(MHD)双扩散对流,数值研究了Dufour和Soret效应对流动的影响.用Crank-Nicolson型的隐式有限差分法,按三对角矩阵处理,求解无量纲的非线性控制方程.详细地研究了问题中出现的各种参数对不稳定无量纲的速度、温度和浓度曲线的影响.进一步地,给出并分析了表面摩擦因数、Nus-selt数和Sherwood数随时间的变化.研究结果表明,不稳定速度、温度和浓度分布曲线,受Dufour和Soret的影响十分显著.随着Dufour数的增加或者Soret数的减小,表面摩擦因数和Sherwood数都在减小,而Nusselt数在增加.研究发现,当磁场参数增加时,边界层中的速度和温度在减小.

Numerical Investigation of the Dufour and Soret Effects on Unsteady MHD Natural Convection Flow Past a Vertical Plate Embedded in a Non-Darcy Porous Medium

The Dufour and Soret effects on unsteady,two-dimensional,magnetohydrodynamics(MHD) double-diffusive free convective flow of an electrically-conducting fluid past a vertical plate embedded in a non-Darcy porous medium were investigated numerically.The governing non-linear dimensionless equations were solved using an implicit finite difference scheme of Crank-Nicolson type with a tri-diagonal matrix manipulation.The effects of various parameters entering into the problem on the unsteady dimensionless velocity,temperature and concentration profiles were studied in detail.Furthermore,the time variation of the skin friction coefficient,the Nusselt number and the Sherwood number were presented and analyzed.The results of the present investigation show that the unsteady velocity,temperature and concentration profiles are substantially influenced by the Dufour and Soret effects.As the Dufour number increases or the Soret number decreases,both the skin friction and the Sherwood number decrease,while the Nusselt number increases.It is found that,when the magnetic parameter increases,the velocity and temperature decrease in the boundary layer.