黏性流体在光滑横管外壁成膜机理研究

Study of liquid film formed on horizontal tube surface

采用低雷诺数、小流量模型对黏性流体在水平管外形成的薄液膜的流速以及膜厚分布进行分析和计算 ;给出了边界层坐标系的二维边界层方程 ,求得了其相似性解 ;根据液膜自由表面上的运动学边界条件 ,给出关于膜厚的一阶偏微分方程 ,利用特征线法求得了膜厚分布的数值解。结果表明 :重力驱动在光滑横管外壁面白发形成均匀的液膜是不可能实现的 ,必须外加一个能产生特殊流场的气刀来改变其原有受力情况 ,才有可能实现均匀液膜。在某一确定的时刻 ,膜厚沿着 x轴逐渐增厚 ;随着时间的推移 ,各处膜厚逐渐减小。

Based on the low Reynold number and small flux model, the velocity and thickness of the liquid film outside the horizontal tube were studied. According to the character of the object, the continuity equation and the Navier Stokes equation in boundary layer coordinates were adopted and the similarity solution was derived. According to the boundary condition of the free surface, the paper gives the first order partial differential equation of the thickness of liquid film and uses characteristic line method to achieve the numerical solution. The result shows that it is infeasible to achieve uniform liquid film outside the horizontal tube under the action of gravity and it is necessary to add a device to generate a special flow field. The result also indicates that at special time the film thickness increases along x direction and along time the film thickness of everywhere reduces, which is important to determine the structure of the device and the fixed position.