Yan L, Thompson K E, Valsaraj K T
Department of Chemical Engineering, Louisiana State University, South Stadium Dr., Baton Rouge, LA 70802, USA.
J Colloid Interface Sci. 2006 Jun 15;298(2):832-44. doi: 10.1016/j.jcis.2006.01.019. Epub 2006 Feb 17.
Using a new computational model, we have studied the dynamics and coalescence of a pair of two-dimensional droplets in pressure-driven flow through a constricted capillary tube, which is a prototype problem for the analysis of the interaction of emulsion droplets in porous media. We present simulations that quantify the effects of various system parameters on the droplet stability. These include the capillary number, the interfacial tension, the suspended-to-suspending-phase viscosity ratio, the valence and concentration of added electrolytes, the droplet-to-pore-size ratio, the pore-body-to-throat-size ratio, and the type of pore geometry. Our simulations show that the capillary number Ca plays an important role in determining whether the drops coalesce. At low Ca, drops deform only slightly and coalescence occurs at the entrance of the pore throat, whereas significant deformation enables the drops move through the pore without coalescence at high Ca. Coalescence is favored at intermediate values of the viscosity ratio. The destabilizing effect of added electrolytes is found to be insignificant for 10-mum drops, but significant for micron-size drops. Among the geometric-related parameters, the drop-to-pore-size ratio is the most significant.
我们使用一种新的计算模型，研究了在压力驱动下通过收缩毛细管的二维液滴对的动力学和聚并情况，这是分析多孔介质中乳液液滴相互作用的一个典型问题。我们给出了量化各种系统参数对液滴稳定性影响的模拟结果。这些参数包括毛细管数、界面张力、悬浮相和连续相的粘度比、添加电解质的化合价和浓度、液滴与孔径比、孔体与喉径比以及孔几何形状类型。我们的模拟表明，毛细管数Ca在决定液滴是否聚并方面起着重要作用。在低Ca值时，液滴仅轻微变形，聚并发生在孔喉入口处；而在高Ca值时，显著的变形使液滴能够在不聚并的情况下通过孔隙。在粘度比的中间值时有利于聚并。发现添加电解质对10微米液滴的去稳定作用不显著，但对微米尺寸的液滴显著。在与几何相关的参数中，液滴与孔径比最为显著。
