含活性剂液滴铺展过程中的指进特征  

Fingering Feature During Droplet Spreading Containing Insoluble Surfactuants on Precursor Film

作　　者：叶学民[1] 王媛媛[1] 李春曦[1] 

机构地区：[1]电站设备状态监测与控制教育部重点实验室,华北电力大学,河北保定071003

出　　处：《华北电力大学学报（自然科学版）》2016年第5期75-82,共8页Journal of North China Electric Power University：Natural Science Edition

基　　金：国家自然科学基金资助项目(11202079);河北省自然科学基金资助项目(A2015502058);中央高校基本科研业务费资助项目(13MS97)

摘　　要：含活性剂液滴放置在预置液膜上或固体壁面上时,表面活性剂浓度梯度将驱动液滴向周围铺展,并在铺展前沿处呈现出复杂的指进现象。通过数值模拟重现了含不溶性活性剂液滴在预置液膜表面铺展过程中的指进现象,分析了指进现象中不同手指的指长和指宽的增长率,结合液膜厚度的功率谱图,给出了导致液滴铺展最不稳定的最危险扰动波数。研究表明:因初始扰动的存在,在液滴底部的液膜最薄区域产生指进现象,且随时间延续,手指不断伸长、变宽、分叉,指进现象更加显著;施加不同形式的初始扰动呈现的指进现象有所区别:施加余弦扰动下的指进现象中长短手指分布较匀称,而施加随机扰动下的指进现象中长短手指分布均匀性较差,呈随机特征;在当前计算参数情形下,影响液滴铺展稳定性的最危险扰动波数为k=10。When a droplet with surfactants is deposited on the precursor film or solid substrate,the spreading process will be presented due to the concentration gradient of the surfactant. Due to the existence of initial disturbance,the thinning region of the drop spreading shows complex patterns,namely,the fingering phenomena. In the present paper,the fingering phenomenon during the spreading of a droplet with insoluble surfactants on precursor film is recreated by numerical simulation,and the growth rates of finger length and width of different fingers are examined. The power spectrum of the film thickness is investigated and the most unstable wave number is found. The results show that the fingers appear in the thinning region at the bottom of drop,and these fingers become longer,wider and bifurcate with the spreading process. The fingering phenomena present similar features when exerting different forms of initial disturbance： the finger length distribution is symmetrical under the cosine disturbance while the finger length distribution uniformity is poor under the random disturbance. The most unstable perturbation wave number k is 10 under the present calculation parameters.

关 键 词：活性剂液滴 铺展 指进现象 功率谱 

分 类 号：O363[理学—流体力学] TQ021[理学—力学]