固液界面效应影响竖壁沟流波动研究

The Effect of Interfacial Interaction of Liquid and Solid Surface on the Wavy Behavior of Rivulet Flowing Downward along a Vertical Plate

基于最小能量原理分析的竖壁沟流流动模型,认为当壁面为存在接触角滞后的非理想表面时,其控制方程的边界条件与滞后接触角有关,并分析了流量存在波动时沟流厚度的波动原因和范围。实验研究了一些液体在不同表面上的沟流流动,结果表明了沟流波动与界面效应有关的假设的合理性,沟流的实际厚度介于由滞后角限定的某一范围内,并且与沟流平均流量有关。若流率波动未超出由滞后接触角及沟流基础流量限定的范围时,沟流只在厚度方向发生波动;若流率波动超出这一范围,则沟流在宽度方向也开始伸缩。

Based on the principle of the minimum total energy （MTE）, the analysis of the laminar liquid rivulet flowing downward along a vertical plate was conducted theoretically and experimentally. The contact angle hysteresis of the solid surface was taken into account in the boundary conditions of the governing equations. The mechanism and possibility of the wave occurrence on the free surface of the rivulet were discussed. In addition, the maximum liquid film thickness of the rivulet influenced by the contact angle hysteresis was experimentally measured. The analytical results and the visual photos show that the shape of the wave on the free surface of rivulet does relate to the interfacial interaction between the liquid and solid surface as well as the average flow rate, The maximum film thickness of the rivulet changes with respect to the contact angle hysteresis. If the change of flow rate in the rivulet is less than a critical value determined by the contact angle hysteresis and the initial flow rate, then only the rivulet thickness may exhibit a waving behavior in terms of fluid flow rate; otherwise the rivulet will expand in width as well.