Experimental study on dynamics of double emulsion droplets flowing through the Y-shaped bifurcation

Abstract

Dynamic behaviors of double emulsion droplets flowing through the Y-shaped bifurcation are experimentally studied and the influences of droplet length, droplet velocity, and liquid viscosity are particularly discussed. The flow patterns of double emulsion droplets are categorized by typical features in motion, namely the number of interfacial breakups and the coupling effect between interfaces. Critical conditions for the existence of the coupling effect are determined by the relative difference between the residence time of inner and outer droplets. Influences of the droplet length and velocity on the transition laws of flow patterns are summarized, and the corresponding dynamic mechanisms are discussed through characteristics of the interfacial deformations. Breakup conditions of inner and outer droplets are individually identified and their variations in liquid systems with different viscosity ratios are analyzed with the aid of the built theory of single emulsion droplets. Universal phase diagrams of the flow patterns are established by taking into account the physical parameters of both inner and outer droplets, which characterize all working forces including the viscous force, the squeezing force, the interfacial tension, and the coupling force that is the unique feature during the breakup of multiple interfaces.