冲击作用下液滴在环境液体中的演变过程及主导因素  

Research on key factors for the drop evolution process in ambient liquid under an impact

作　　者：廖斌[1,2] 朱雨建[1] 杨基明[1] LIAO Bin ZHU YuJian YANG JiMing(Department of Modern Mechanics, University of Science and Technology of China, Hefei 230027, Chin College of Civil Engineering and Architecture, Anhui Polytechnic University, Wuhu 241000, China)

机构地区：[1]中国科学技术大学近代力学系,合肥230027 [2]安徽工程大学建筑工程学院,芜湖241000

出　　处：《中国科学：物理学、力学、天文学》2017年第9期41-50,共10页Scientia Sinica Physica,Mechanica & Astronomica

基　　金：国家自然科学基金(编号:11572313;11621202)资助

摘　　要：采用实验与计算流体力学(CFD)相结合的方法对冲击作用下液滴在环境液体中的演变过程进行了研究,重点针对液膜破碎之前液滴的4种典型演变模式所伴随的流场细节进行了较为深入的探讨.结果表明,液滴演变过程与涡强度有较强关联:涡强度越大,液滴演变模式越剧烈,演变过程中出现环状射流持续翻转现象;反之,演变过程中无环状射流生成甚至出现液滴变形回复现象.进一步对液滴内部环状射流的生成与发展机理进行研究发现,涡的演变与界面约束之间存在一种竞争机制:涡的演变促进界面的进一步变形,而界面约束起着相反的抑制作用.这一竞争机制通过有无界面张力条件下液滴变形的CFD结果得到了进一步揭示.A mixed flow of two immiscible liquids may form drops of one liquid in another. Deformation and breakup of a drop will occur when there is sufficiently severe interaction between the drop and the ambient liquid. In this paper, the drop evolution process in ambient liquid under an impact was studied based on an experimental method combined with computational fluid dynamics （CFD）. In the experiment conducted on a free-falling drop-tower facility, four typical drop deformation modes, namely oscillatory mode, bag mode, cap mode, and mushroom mode, sorting in order of deformation severity, were captured with high speed photography. In the numerical simulation, the Front-Tracking method was adopted to predict the drop evolution process, and a satisfactory agreement was obtained between the experimental and numerical results. After the verification a further numerical analysis was carded out for the mechanism of the four types of drop deformation modes before the breakup of liquid film, for which the key factors that dominate the drop evolution process were also discussed. It is found that the drop evolution is strongly affected by vortex strength, namely the greater the vortex strength is, the more severe the evolution mode will be, during which an annular jet will be generated and continues to turn over; on the contrary, there is no annular jet formation or even drop deformation recovery phenomenon occurs. After a further research on the generation and development of the annular jet inside the drop, we find that there is a competition mechanism between vortex evolution and interfacial constrain, in which deformation of the interface is promoted by vortex evolution, while interface constrain plays an inhibitory role. Finally, the competitive mechanism has been further revealed by the numerical results of drops deformation under the conditions with/without interfacial tension.

关 键 词：液滴变形 环状射流 涡 界面约束 

分 类 号：O35[理学—流体力学]