Asymmetric breakup of a droplet in an axisymmetric extensional flow

查看全文 作　　者：Dongming [1,2]Yu;Manman [1]Zheng;Taoming [1]Jin;Jingtao [1]Wang 机构地区：[1]School of Chemical Engineering and Technology, Tianjin University;[2]Sinopec Shanghai Engineering Co., Ltd. 出　　处：《Chinese Journal of Chemical Engineering》索引2016年第24卷第1期,共8页 基　　金：Supported by Major State Basic Research Development Program of China(2012CB720305);the National Natural Science Foundation of China(21376162) 摘　　要：The asymmetric breakups of a droplet in an axisymmetric cross-like microfluidic device are investigated by using a three-dimensional volume of fluid(VOF) multiphase numerical model. Two kinds of asymmetries(droplet location deviation from the symmetric geometry center and different flow rates at two symmetric outlets) generate asymmetric flow fields near the droplet, which results in the asymmetric breakup of the latter. Four typical breakup regimes(no breakup, one-side breakup, retraction breakup and direct breakup) have been observed.Two regime maps are plotted to describe the transition from one regime to another for the two types of different asymmetries, respectively. A power law model, which is based on the three critical factors(the capillary number,the asymmetry of flow fields and the initial volume ratio), is employed to predict the volume ratio of the two unequal daughter droplets generated in the direct breakup. The influences of capillary numbers and the asymmetries have been studied systematically in this paper. The larger the asymmetry is, the bigger the oneside breakup zone is. The larger the capillary number is, the more possible the breakup is in the direct breakup zone. When the radius of the initial droplet is 20 μm, the critical capillary numbers are 0.122, 0.128, 0.145,0.165, 0.192 and 0.226 for flow asymmetry factor AS= 0.05, 0.1, 0.2, 0.3, 0.4 and 0.5, respectively, in the flow system whose asymmetry is generated by location deviations. In the flow system whose asymmetry is generated by two different flow rates at two outlets, the critical capillary numbers are 0.121, 0.133, 0.145, 0.156 and 0.167 for AS= 1/21, 3/23, 1/5, 7/27 and 9/29, respectively. 关 键 词：轴对称 液滴 对称破裂 拉伸流动 不对称分裂 毛细管数 流动系统 位置偏差