UNSTEADY MIXED CONVECTION FLOW IN STAGNATION REGION ADJACENT TO A VERTICAL SURFACE
UNSTEADY MIXED CONVECTION FLOW IN STAGNATION REGION ADJACENT TO A VERTICAL SURFACE
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DOI：
10.1007/bf01590239
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发表时间：
1991-01-01
期刊：
影响因子：
--
通讯作者：
NATH, G
中科院分区：
文献类型：
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作者：
DEVI, CDS;TAKHAR, HS;NATH, G
研究了垂直表面停滞区的非定常二维层流混合对流，其中浮力是由温度梯度和浓度梯度共同产生的。流场和温度场的不稳定性是由随时间变化的自由流速度引起的。任意壁面温度和浓度，以及任意表面热量和质量通量的变化都被考虑。将Navier-Stokes方程、能量方程和浓度方程这三个相互耦合的非线性偏微分方程组化为一组非线性常微分方程组。用边界层近似法进行了分析，并讨论了两种解之间的差别。利用打靶法对浮力辅助区和浮力对抗区的控制常微分方程进行了数值求解。表面摩擦系数、传热系数和传质系数随浮力参数的增大而增大。然而，表面摩擦系数随着参数λ的增加而增加，这代表了自由流速度的不稳定性，但传热和传质系数降低。在浮力反向流动的情况下，解不存在超过一定的临界值的浮力参数。此外，对于一定范围内的浮力参数的双重解决方案存在。
The unsteady two-dimensional laminar mixed convection flow in the stagnation region of a vertical surface has been studied where the buoyancy forces are due to both the temperature and concentration gradients. The unsteadiness in the flow and temperature fields is caused by the time-dependent free stream velocity. Both arbitrary wall temperature and concentration, and arbitrary surface heat and mass flux variations have been considered. The Navier-Stokes equations, the energy equation and the concentration equation, which are coupled nonlinear partial differential equations with three independent variables, have been reduced to a set of nonlinear ordinary differential equations. The analysis has also been done using boundary layer approximations and the difference between the solutions has been discussed. The governing ordinary differential equations for buoyancy assisting and buoyancy opposing regions have been solved numerically using a shooting method. The skin friction, heat transfer and mass transfer coefficients increase with the buoyancy parameter. However, the skin friction coefficient increases with the parameter lambda, which represents the unsteadiness in the free stream velocity, but the heat and mass transfer coefficients decrease. In the case of buoyancy opposed flow, the solution does not exist beyond a certain critical value of the buoyancy parameter. Also, for a certain range of the buoyancy parameter dual solutions exist.