活性剂对表面声波作用下薄液膜铺展的影响  

Effect of surfactants on thin film spreading under influence of surface acoustic wave

作　　者：李春曦[1] 施智贤 庄立宇 叶学民[1] Li Chun-Xi;Shi Zhi-Xian;Zhuang Li-Yu;Ye Xue-Min(Department of Power Engineering,North China Electric Power University,Baoding 071003,China)

机构地区：[1]华北电力大学动力工程系

出　　处：《物理学报》2019年第21期198-208,共11页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:51876065)资助的课题~~

摘　　要：针对表面声波作用下含不溶性活性剂的部分润湿薄液膜的铺展过程,推导出了液膜厚度和表面活性剂浓度的无量纲演化方程组,通过数值计算研究了声波引起的漂移流主导的液膜铺展过程及漂移流与毛细力共同控制的铺展过程.结果表明表面声波驱使液膜铺展及移动,而活性剂进一步促进了液膜的铺展过程,且当活性剂存在时受漂移流与毛细力共同控制的铺展过程中出现了铺展半径收缩的现象,使得液膜达到平衡状态所需的时间更长.另外,液膜最大厚度和铺展半径的变化速度随着分离压与活性剂浓度的相关系数a值、Marangoni数M值的增大而加快.For the spreading of thin and free film of a partially wetting liquid with insoluble surfactant under the influence of surface acoustic wave,the dimensionless evolution equations governing the spreading dynamics are derived.The evolution equations contain the film thickness and the surface concentration of insoluble surfactant.Assuming that the thickness of the thin film is much smaller than the wavelength of sound in the liquid,the sound leaking off the surface acoustic wave cannot be sustained in the liquid film,and the acoustic radiation pressure and attenuation of the acoustic wave in the solid are both weak.Then the films spreading under different physical mechanisms are observed by numerical simulation.The results show that the surface acoustic wave drives the liquid film to spread and move.When the capillary stress is weak and the liquid film spreading is mainly controlled by the drift induced by surface acoustic wave,the spreading process consists of rapid spreading stage and balancing stage,and the Marangoni effect caused by uneven distribution of surfactant makes the liquid film spread faster in the first stage.When the capillary stress and the drift jointly dominate film spreading,the spreading process contains three stages,i.e.spreading stage,contracting stage and balancing stage.The effect of surfactant accelerates the spreading process,but the existence of contracting stage makes it take longer for the film to reach equilibrium.In addition,the disjoining pressure used in this paper promotes the liquid film spreading,as well as the Marangoni effect.As the correlation coefficient between disjoining pressure and surfactant concentration,a,and the Marangoni number,M,increase,the maximum thickness and the spreading radius of liquid film change faster.

关 键 词：表面声波 活性剂 铺展 部分润湿薄液膜 

分 类 号：TB383.2[一般工业技术—材料科学与工程] TB559[理学—物理]