多孔介质——自由流界面应力跳跃条件下流动特性解析解

对非对称多孔介质--自由流复合通道内多孔介质内部及多孔介质与自由流体界面处复杂质量、动量输运特性进行研究. 在多孔介质区采用Brinkman-extended Darcy模型并结合速度连续,剪切应力跳跃的界面条件对此复合通道内流体的传递现象进行求解,提出了考虑界面应力跳跃时非对称复合通道各区域流体运动速度及摩擦系数的解析式,分析了界面应力跳跃系数,达西数及无量纲多孔层偏心厚度对流体速度及摩擦系数的影响. 结果表明:改变界面性质可在一定条件下明显控制各区域流体速度分布;在达西数、多孔层偏心厚度一定情况下,界面应力系数的增大会使界面流速减小,而使流体摩擦系数增大,特别是界面应力系数小于0的情况下变化更明显,此时若不考虑界面应力系数则会造成较大误差. 当界面应力系数及多孔层偏心厚度均为较小负数值时,改变多孔层偏心厚度对界面速度的影响要大于改变界面应力系数的情况;而当界面应力系数及多孔层偏心厚度为较大正数值时,情况则相反. 较大达西数下,界面应力系数及多孔层偏心厚度对流体摩擦系数的影响均较大,继续减小达西数至一定程度时,界面应力系数对流体摩擦系数的影响可忽略不计而认为只与多孔层偏心厚度相关,且对较大多孔层偏心厚度更敏感. 

ANALYTICAL SOLUTION FOR POROUS-FLUID FLOW CHARACTERISTICS WITH STRESS JUMP INTERFACIAL CONDITION

The complicated mass and momentum transfer problems in the porous region,especially at the interface between porous and free fluid region were analyzed in an asymmetric and coupled porous-fluid channel. By taking the Brinkman-extended Darcy model in the porous region with the velocity continuity and the shear stress jump interface conditions, the fluid transfer characteristics were solved. The analytical expressions for the fluid flow velocity of each region and friction coefficient in the coupled asymmetric channel were proposed by considering the stress jump interfacial condition. Then the effects of interfacial stress jump coefficient, Darcy number and dimensionless off-center thickness of porous layer on fluid flow velocity and friction coefficient were studied. The results show that under certain conditions changing the interface property can obviously control the velocity profile in each region of the coupled channel. For certain values of Darcy number and porous off-center thickness, increasing the interfacial stress coefficient has a reducing effect on the interfacial velocity but an increasing effect on the fluid friction coefficient, and the effect is more obvious when the interfacial stress coefficient is less than 0, in this case that without considering the effect of the interfacial stress coefficient can cause larger error. When both the interfacial stress coefficient and the porous off-center thickness are smaller negative values, the effect by varying the porous off-center thickness on the interfacial velocity is greater than the effect of altering the interfacial stress coefficient, while when the interfacial stress coefficient and the porous off-center thickness of porous layer are larger positive values, the result is quite the opposite. At a larger Darcy number, both the interfacial stress coefficient and porous off-center thickness have greater influence on the fluid friction coefficient; reducing Darcy number to a certain small value, the influence of interfacial stress coefficient on fluid friction coefficient can be neglected and the fluid friction coefficient is only related to the porous off-center thickness, and much more sensitive to a larger porous off-center thickness.