Dynamics and formation of alternating droplets under magnetic field at a T-junction
Dynamics and formation of alternating droplets under magnetic field at a T-junction
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T 形结磁场下交替液滴的动力学和形成
DOI：
10.1016/j.ces.2019.01.053
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发表时间：
2019
影响因子：
4.7
通讯作者：
Guangsheng Luo
中科院分区：
文献类型：
--
作者：
Di Liang;Rui Ma;Taotao Fu;Chunying Zhu;Kai Wang;Youguang Ma;Guangsheng Luo
用高速相机研究了截面积为400 μm × 400 μm的T形结上交变液滴的形成过程。交替的液滴由甘油水溶液和磁流体液滴组成。观察到了两种交替形成的液滴：正常形成和上游液滴挤压形成。磁场的存在延缓了液滴从正常农场向上游液滴挤压形成的转变。研究了两相流流量和磁通密度对磁流体尖端和颈部的动力学及形成周期的影响。结果表明，磁流体的颈缩演化可分为膨胀阶段和夹断阶段。膨胀阶段以铁磁流体流动为主，夹点阶段对流体流动不敏感，是一个自相似过程。在夹点阶段，磁流体尖端长度随时间几乎呈线性增长，且增长速率随流量的增加而增大。液滴的形成周期随着流体流量的增加而缩短。当地层类型为正常地层时，磁场的存在缩短了地层的形成周期。当形成类型为上游液滴挤压区时，磁场的存在延长了形成周期。本文为交变液滴的产生提供了一种新的方法。
The formation process of alternating droplets at the T-junction with a cross-sectional area of 400 μm × 400 μm was investigated using a high-speed camera. The alternating droplets were consisted of glycerol aqueous solution and ferrofluid droplets. Two formation types of alternating droplets were observed: normal formation and the upstream droplet squeezing formation. The existence of the magnetic field delayed the transition from the normal farmation to the upstream droplet squeezing formation. The effects of two-phase flow rate and magnetic flux density on the dynamics of the tip and the neck of the ferrofluid and the formation period were studied. The results show that the neck evolution of ferrofluid could be divided into the expansion stage and pinch-off stage. The expansion stage was dominated by the flow of ferrofluid, and the pinch-off stage was insensitive to fluid flow and was a self-similar process. The length of the tip of ferrofluid increases almost linearly with time during the pinch-off stage, and the increasing rate rose with the flow rates. The formation period of the droplets reduces as the fluid flow rate increases. When the formation type is normal formation, the existence of the magnetic field shortens the formation period. When the formation type is the upstream droplet squeezing regime, the existence of the magnetic field prolongs the formation period. This paper provides a new method for the generation of alternating droplets.