Davis Robert H, Zinchenko Alexander Z
Department of Chemical and Biological Engineering, University of Colorado, Boulder, CO 80309-0424, USA.
J Colloid Interface Sci. 2009 Jun 15;334(2):113-23. doi: 10.1016/j.jcis.2009.02.062. Epub 2009 Apr 8.
This article features recent simulation studies of the flow of emulsions containing deformable drops through pores, constrictions, and granular media. The flow is assumed to be at low Reynolds number, so that viscous forces dominate, and boundary-integral methods are used to determine interfacial velocities and, hence, track the drop motion and shapes. A single drop in a flat channel migrates to the channel centerplane due to deformation-induced drift, which increases its steady-state velocity along the channel. A drop moving towards a smaller interparticle constriction squeezes through the constriction if the capillary number (ratio of viscous deforming forces and interfacial tension forces) is large enough, but it becomes trapped when the capillary number is below a critical value. These concepts then influence the flow of an emulsion through a granular medium, for which the drop phase moves faster than the suspending liquid at large capillary numbers but slower than the suspending liquid at smaller capillary numbers. The permeabilities of the granular medium to both phases increase with increasing capillary number, due to the reduced resistance to squeezing of easily deformed drops, though drop breakup must also be considered at large capillary numbers.
本文介绍了近期关于含可变形液滴的乳液在孔隙、缩颈和颗粒介质中流动的模拟研究。假定流动处于低雷诺数状态，使得粘性力占主导地位，并采用边界积分方法来确定界面速度，进而追踪液滴的运动和形状。在扁平通道中的单个液滴会因变形诱导漂移而迁移至通道中心平面，这会增加其沿通道的稳态速度。当朝着较小的颗粒间缩颈移动时，如果毛细管数（粘性变形力与界面张力之比）足够大，液滴会挤过缩颈，但当毛细管数低于临界值时，液滴会被困住。这些概念随后影响乳液在颗粒介质中的流动，在大毛细管数下，液滴相的移动速度比悬浮液快，但在小毛细管数下比悬浮液慢。颗粒介质对两相的渗透率随毛细管数的增加而增加，这是由于对易变形液滴的挤压阻力减小，不过在大毛细管数下还必须考虑液滴破裂的情况。
