Dolganov P V, Zverev A S, Baklanova K D, Dolganov V K
Institute of Solid State Physics, Russian Academy of Sciences, 142432 Chernogolovka, Moscow district, Russia.
National Research University Higher School of Economics, Moscow 101000, Russia.
Phys Rev E. 2021 Jul;104(1-1):014702. doi: 10.1103/PhysRevE.104.014702.
We observed the formation of small satellite droplets from the bridge at droplet coalescence. Investigations were made using a Hele-Shaw cell in the two-phase region at the nematic-isotropic phase transition. In previous works on coalescence it was considered that before the start of coalescence there exists a bridge between the outer fluid connecting regions on the two sides of the droplets (outer bridge). After the start of coalescence, a bridge connecting the two droplets appears (droplet bridge) and the outer bridge is broken. We have shown that there are coalescence processes where after the start of coalescence both the droplet bridge and the outer bridge can exist. This cardinally changes the coalescence process. During the first coalescence stage the size of the outer bridge decreases and the size of the droplet bridge increases. During the second stage the outer bridge becomes unstable which leads to pinch-off, formation of pointed end domains, secondary instability, splitting of pointed end domains, and formation of satellite droplets. We found the linear dependence of the minimum bridge radius on time near bridge breakup. This behavior confirms the capillary viscous regime of bridge breakup. Our work connects two areas of fluid dynamics: coalescence and breakup with formation of satellite droplets.
我们观察到在液滴聚并过程中，桥处会形成小卫星液滴。研究是在向列相 - 各向同性相转变的两相区域中使用赫勒 - 肖池进行的。在之前关于聚并的研究中，人们认为在聚并开始之前，液滴两侧的外部流体连接区域之间存在一个桥（外部桥）。聚并开始后，会出现连接两个液滴的桥（液滴桥），外部桥断裂。我们已经表明，存在这样的聚并过程，即在聚并开始后，液滴桥和外部桥都可以存在。这从根本上改变了聚并过程。在第一个聚并阶段，外部桥的尺寸减小，液滴桥的尺寸增大。在第二阶段，外部桥变得不稳定，这导致夹断、尖端区域的形成、二次不稳定性、尖端区域的分裂以及卫星液滴的形成。我们发现桥破裂附近最小桥半径与时间呈线性关系。这种行为证实了桥破裂的毛细粘性机制。我们的工作将流体动力学的两个领域联系起来：聚并以及伴随卫星液滴形成的破裂。
