Effect of geometry on droplet formation in the squeezing regime in a microfluidic T-junction

Abstract

In the surface tension-dominated microchannel T-junction, droplets can be formed as a result of the mixing of two dissimilar, immiscible fluids. This article presents results for very low Capillary numbers and different flow rates of the continuous and dispersed phases. Through three-dimensional lattice Boltzmann-based simulations, the mechanism of the formation of ''plugs'' in the squeezing regime has been examined and the size of the droplets quantified. Results for Re c ( 1 show the dependence of flow rates of the two fluids on the length of the droplets formed, which is compared with existing experimental data. It is shown that the size of plugs formed decreases as the Capillary number increases in the squeezing regime. This article clearly shows that the geometry effect, i.e., the widths of the two channels and the depth of the assembly, plays an important role in the determination of the length of the plugs, a fact that was ignored in earlier experimental correlations.

Generation of Oil Droplets in a Non-Newtonian Liquid Using a Microfluidic T-Junction

“…This trend is consistent with other studies where droplet production is controlled by two immiscible streams in a variety of different geometries [7,25,35]. In the squeezing regime, i.e., for Ca ≲ 0.01, the length of the drops can be conveniently expressed with the following scaling equation = α + α , where α1 and α2 are two constants of order one that depend on the junction geometry [10,36,37]. Accordingly, should not depend on Ca if φ is constant.…”

“…, where α 1 and α 2 are two constants of order one that depend on the junction geometry [10,36,37]. Accordingly, L should not depend on Ca if φ is constant.…”

Experimental investigations of non‐Newtonian/Newtonian liquid‐liquid flows in microchannels

“…1,2 The small characteristic dimensions and high surface-to-volume ratio in microdevices enhance the role of surface tension over gravitational forces resulting in patterns different to those observed in large-scale flows. 3,4 Flows of mixtures of two immiscible liquids are very common in chemical processing. The main patterns that have been observed in liquid-liquid microchannel flows are plug, drop, annular, and parallel depending on the competition among interfacial ($r/d), viscous ($lÁu/d), and inertia ($qÁuÁd) forces.…”

CFD analysis of microchannel emulsification: Droplet generation process and size effect of asymmetric straight flow-through microchannels

“…Computational fluid dynamics (CFD) methods have also been used to simulate and analyze droplet generation in microfluidic channel configurations (Sang et al 2008;Kashid et al 2010; Zhou et al 2006;de Menech et al 2008;Gupta and Kumar 2010).…”