粘弹性流体流经竖直表面时的瞬时自然对流

Transient Free Convection Flow of a Visco-Elastic Fluid Over a Vertical Surface

静止流体中,在一个竖直的、不可渗透的等温表面附近,研究粘弹性边界层的流动及其热传导.得到其控制方程,并利用MackCormak技术对其进行数值求解.与先前发表的关于该问题特例的结果相比较,有着很好的一致性.对于不同的粘弹性参数值,图示了速度和温度分布、边界层厚度、Nusselt数、局部摩擦因数等典型结果.一般而言,粘弹性流体与Newton流体相比较,由于拉应力的促进作用,流体动力边界层里的速度是增加的,热边界层里的温度是下降的.粘弹性参数值越高,摩擦因数和传热系数越高.

The viscoelsatic boundary layer flow and heat transfer near a vertical isothermal impermeable surface and in a quiescent fluid were examined.The governing equations were formulated and solved numerically using the MackCormak＇s technique.A comparison with previously published results on special cases of the problem shows excellent agreement.Representative results for the velocity and temperature profiles,boundary layer thicknesses,Nusselt numbers and local skin friction coefficients are shown graphically for different values of viscoelsatic parameter.In general,it is found that the velocities increase inside the hydrodynamic boundary layers and the temperatures decrease inside the thermal boundary layers for the viscoelsatic fluid as compared to the Newtonian fluid due to favorable tensile stresses.Consequently the coefficient of friction and heat transfer are enhanced for higher viscoelsatic parameter.