论文标题
微通道Y期间液滴对的相互作用和分解
Interaction and breakup of droplet pairs in a microchannel Y-junction
论文作者
论文摘要
我们结合了理论，数值模拟和实验，以研究两个相同的液滴进入Y结的分解，并以受控的空间偏移为止，第二滴通过该空间偏移。基于完全解决的3D模拟，我们描述了导致破裂的流体物理。缩放参数，数值仿真和实验始终表明，对于小初始偏移，分解总是在液滴片段量的情况下，取决于偏移。在临界偏移量之上，随着毛细管数的增加，液滴依次进入收缩而不会分解。我们的结果与理解通过线性收敛通道的密集乳液中的分解行为有关，导致收缩。这种几何形状通常用于在液滴微流体应用中对液滴含量的序列询问，其中液滴分解可以限制该过程的最大吞吐量。对于最高$ ca \ simeq10^{ - 2} $的毛细管数，Y期中的两滴系统的结果与通过线性收敛通道流过的密集乳液中的分解观测一致。在两滴系统中，初始偏移与产生的分解之间的确定性关系表明，在致密乳液的破裂中观察到的随机性是由多滴相互作用引起的。从实验中确定的初始偏移片段和液滴片段之间的线性关系中的预制剂的数值与从完全分辨的数值模拟中提取的数值略有不同。这种差异表明，即使在非常高的表面活性剂浓度下，限制速率表面活性剂吸附动力学也允许Marangoni应力开发和修改液滴动力学。
We combine theory, numerical simulation and experiments to investigate the breakup of two identical droplets entering a Y-junction with controlled spatial offset by which the second droplet trails the first. Based on fully resolved 3D simulations, we describe the flow physics leading to breakup. Scaling arguments, numerical simulation and experiments consistently show that for small initial offset, breakup always occurs with the droplet fragment volume depending linearly on the offset. Above a critical offset, which increases with the capillary number, the droplets enter the constriction sequentially without breakup. Our results are relevant for understanding the breakup behavior in a dense emulsion flowing through a linearly converging channel leading to a constriction. Such geometry is commonly used for the serial interrogation of droplet content in droplet microfluidic applications, where droplet breakup can limit the maximum throughput for such process. For capillary numbers up to $Ca\simeq10^{-2}$, the results from the two-droplet system in a Y-junction are consistent with breakup observations in dense emulsions flowing through a linearly converging channel. The deterministic relation between initial offset and resulting breakup in the two-droplet system suggests that the stochasticity that is observed in the breakup of a dense emulsion arises from multi-droplet interactions. The numerical value of the prefactor in the linear relation between initial offset and droplet fragment volume determined from experiments differs slightly from the one extracted from fully resolved numerical simulations. This discrepancy suggests that even at very high bulk surfactant concentrations, the rate-limiting surfactant adsorption kinetics allows for Marangoni stresses to develop and modify the droplet dynamics.
