Zhang Jinggang, Cui Haihang, Liu Haihu, Chen Li, Zhang Xitong, Li Chenlu
School of Building Services Science and Engineering, Xi'an University of Architecture and Technology, Xi'an 710055, China.
School of Energy and Power Engineering, Xi'an Jiaotong University, 28 West Xianning Road, Xi'an 710049, China.
Langmuir. 2023 Sep 26;39(38):13735-13747. doi: 10.1021/acs.langmuir.3c02003. Epub 2023 Sep 13.
The role of surfactants in the flow of a droplet driven by a pressure gradient through a constricted microchannel is simulated by using our recently developed lattice Boltzmann method. We first study the surfactant role on a droplet flowing through a microchannel with a shrunken square section under different surfactant concentrations and capillary numbers (i.e., imposed pressure gradients). As the surfactant concentration increases, the droplet flow regime first changes from the flow regime I of the droplet getting stuck at the entrance of the constricted channel to the flow regime II of the droplet flowing through the constricted channel with breakup, and then to the flow regime III of the droplet flowing through the constricted channel without breakup. As the capillary number increases, the surfactant role on the number of mother droplets breaking up and the time of mother droplets completely flowing through the constricted section tend to decrease, suggesting that the surfactant effects are gradually weakened. Then, a phase diagram describing how the surfactant concentration and capillary number affect the droplet flow regime is presented. As the surfactant concentration increases, the critical capillary number that distinguishes droplet flow regimes I from II gradually decreases, while the critical capillary number that distinguishes droplet flow regimes II from III first increases and then decreases.
通过使用我们最近开发的格子玻尔兹曼方法，模拟了表面活性剂在由压力梯度驱动的液滴通过收缩微通道流动中的作用。我们首先研究了在不同表面活性剂浓度和毛细管数（即施加的压力梯度）下，表面活性剂对液滴在具有收缩方形截面的微通道中流动的作用。随着表面活性剂浓度的增加，液滴流动状态首先从液滴卡在收缩通道入口处的流动状态I转变为液滴通过收缩通道并破碎的流动状态II，然后转变为液滴通过收缩通道而不破碎的流动状态III。随着毛细管数的增加，表面活性剂对母液滴破碎数量和母液滴完全流过收缩段时间的作用趋于减小，这表明表面活性剂的作用逐渐减弱。然后，给出了一个描述表面活性剂浓度和毛细管数如何影响液滴流动状态的相图。随着表面活性剂浓度的增加，区分液滴流动状态I和II的临界毛细管数逐渐减小，而区分液滴流动状态II和III的临界毛细管数先增加后减小。
