竖直平板上含活性剂液膜排液过程不稳定现象的数值模拟

Numerical Simulation of Instability of Film Drainage with Surfactants on a Vertical Plate

基于润滑理论建立了表面速度、液膜厚度和活性剂浓度的二维演化模型。在弯月面位置施加展向扰动,通过数值计算得到了该局部扰动随排液的发展过程和Marangoni效应的影响规律。结果表明:施加展向扰动后,弯月面处立即出现扰动波纹,但扰动因重力阻碍随排液迅速减弱;在排液后期,弯月面区域扰动波纹再现并逐渐向顶端发展。随Marangoni效应的增强,在排液前期,活性剂逆流区扩大;在排液后期,液膜扰动能量增长度、波纹不规则性加强,进而对液膜的稳定产生了不利影响。

Based on lubrication theory, the 2D evolution model was established describing surface velocity, film thickness and surfactant concentration. With imposing disturbances at meniscus position,the evolution of local disturbances on drainage was examined by numerical calculation, and the influence of Marangoni effect was further explored. The results showed that unstable waves appeared at the meniscus due to imposed disturbances, whereas the disturbances were weakened rapidly because of gravity. In the late stage of drainage, the transverse disturbances at the meniscus had a significant effect,then the disturbance waves reappeared and gradually developed towards the top of film. With Marangoni effect enhancing, the counter-current region with surfactants was expanded in the early stage of drainage,while disturbing energy on the film surface was increased and waves tended to intensify in the late stage of drainage, which was detrimental to the stability of film.