含表面活性剂液膜的去湿特性

Investigation on Dewetting Dynamics of Thin Liquid Film Containing Insoluble Surfactant

针对存在壁面滑移的含非溶性表面活性剂液膜在固体表面的去湿过程,应用基于润滑理论建立的液膜厚度及表面活性剂浓度的演化方程组,采用PDECOL程序对液膜演化历程进行了数值模拟,并分析了各特征参数对去湿特性的影响.结果表明,Marangoni效应对垂直方向上液膜厚度的变化影响微弱,液膜厚度的变化由分离压及毛细力所主导;Marangoni数对最终形成的去湿结构的影响并不显著,减小毛细力数则有助于抑制去湿过程的发展;增大滑移系数可以加速去湿进程,而最终形成的去湿结构明显缩小;增大平衡液膜厚度,液膜表面变形程度减小,液膜厚度逐渐趋于平稳.

Under slip boundary conditions, the dewetting of thin liquid films in the presence of insoluble surfactant monolayer was considered. Coupled nonlinear governing equations for the film thickness and surfactant concentration based on boundary layer theory were employed. The dewetting evolution of films was simulated using PDECOL program and the numerical results were presented, while the effects of characteristic parameters on dewetting process were discussed. The results show that the impact of Marangoni effect on the change rate of films thickness is not significant in vertical direction, the change rate of films thickness is dominated by disjoining pressure and capillary stress. The influence of Marangoni number M on static dewetted structures is not significant, and decreasing capillary number C will suppress the dewetting phenomenon effectively. Increasing slip coefficient βwill accelerate the dewetting process and shorten the dewetted structures. Increasing equilibrium film thickness lc will lessen the deformation degree of sur face and thereby lead the film thickness to be stabilized.