多孔介质中受限层流冲击射流的流动与换热特性

基于两区(two-domain)模型采用基于预处理的时间推进法对铺设有多孔介质层的恒温平板在受限层流冲击射流作用下的流动与换热特性进行了研究，其中多孔区域动量方程采用Brinkman-Forchheimer拓展Darcy模型，能量方程则采用局部热平衡(LTE)模型，并对porous/fluid交界面切应力跳跃条件对多孔介质冲击射流的影响进行了分析。流体的控制方程采用基于密度的有限体积法来求解，并针对于多孔区域低速流动特点采用相对应的预处理矩阵来消除控制方程的刚性。还对Reynolds数、孔隙率、Darcy数、热导率比、多孔介质层厚度等参数的变化对流动结构及换热特性的影响进行了分析。研究结果表明，在目前的计算条件下，在其他参数一定时，Reynolds数、孔隙率对通道内流动结构的影响有限；Darcy数、多孔介质层厚度则对流动结构的影响很大；上述参数对受冲击平板的总体换热性能均有明显的影响。在受冲击平板上铺设适当厚度的高渗透率、高热导率的多孔材料能有效地增强换热性能。

Flow and heat transfer characteristics of confined laminar impinging jet on plate with porous layer

The preconditioned density-based algorithm and two-domain approach were used to investigate the fluid flow and heat transfer characteristics of confined laminar impinging jet on a plate covered with porous layer.In the porous zone, the momentum equations were formulated by Darcy-Brinkman-Forchheimer model, and the thermal equilibrium model was adopted for energy equation.At the porous/fluid interface, the influence of stress-jump interfacial condition was analyzed.The governing equations were solved by preconditioned density-based infinite-volume method, with preconditioning matrix for equations of porous domain adopted, aiming to eliminate the equation stiffness of porous seepage flow.The effects of Reynolds number, porosity, Darcy number, ratio of thermal conductivities, and porous layer thickness on the flow pattern and local heat transfer were studied.Results indicate that Reynolds number and porosity do not influence the flow pattern of porous channel strongly, while the effects of Darcy number and porous layer thickness are significant.All the parameters mentioned above have obvious influence on local overall heat transfer performance.