Effective interfacial tension in flow-focusing of colloidal dispersions: 3-D numerical simulations and experiments
Effective interfacial tension in flow-focusing of colloidal dispersions: 3-D numerical simulations and experiments
复制标题
DOI：
10.1017/jfm.2019.566
复制
发表时间：
2019-10-10
影响因子：
3.7
通讯作者：
Lundell, Fredrik
中科院分区：
文献类型：
--
作者：
Gowda, Krishne, V;Brouzet, Christophe;Lundell, Fredrik
两种可混溶流体之间的界面是瞬态的，在达到完全分子混合之前作为非平衡状态存在。然而，在这种界面的存在期间，这通常发生在相对短的时间尺度上，在两种液体之间的边界处的组成梯度引起有效地模拟界面张力的应力。在这里，我们结合联合收割机的数值模拟和实验，研究胶体纤维分散体和它自己的溶剂之间的有效界面张力的影响，在微流控系统中的流动。在流动聚焦通道中，分散体作为芯流注入，芯流通过其溶剂作为鞘流流体动力学地聚焦。这导致形成一个长的流体线程，其特征在于在三维使用光学相干断层扫描和模拟使用的流体体积的方法。在螺纹拓扑结构和速度流场方面，模拟的流动和螺纹几何形状非常接近地再现了实验结果。通过改变界面张力数值，我们表明，它控制线程的发展，这可以描述一个有效的毛细管数。此外，我们证明了所应用的方法提供了测量超低但动态高度显着的有效界面张力的手段。
An interface between two miscible fluids is transient, existing as a non-equilibrium state before complete molecular mixing is reached. However, during the existence of such an interface, which typically occurs at relatively short time scales, composition gradients at the boundary between the two liquids cause stresses effectively mimicking an interfacial tension. Here, we combine numerical modelling and experiments to study the influence of an effective interfacial tension between a colloidal fibre dispersion and its own solvent on the flow in a microfluidic system. In a flow-focusing channel, the dispersion is injected as core flow that is hydrodynamically focused by its solvent as sheath flows. This leads to the formation of a long fluid thread, which is characterized in three dimensions using optical coherence tomography and simulated using a volume of fluid method. The simulated flow and thread geometries very closely reproduce the experimental results in terms of thread topology and velocity flow fields. By varying the interfacial tension numerically, we show that it controls the thread development, which can be described by an effective capillary number. Furthermore, we demonstrate that the applied methodology provide the means to measure the ultra-low but dynamically highly significant effective interfacial tension.