A flow map for core/shell microdroplet formation in the co-flow Microchannel using ternary phase-field numerical model

Abstract

Core/shell microdroplets formation with uniform size is investigated numerically in the co-flow microchannel. The interface and volume fraction contour between three immiscible fluids are captured using a ternary phase-field model. Previous research has shown that the effective parameters of microdroplet size are the physical properties and velocity of the three phases. By adjusting these variables, five main flow patterns are observed in numerical simulations. A core/shell dripping/slug regime is observed when the inertia of the continuous phase breaks the flow of the core and shell phases and makes a droplet. In the slug regime, the continuous phase has less inertia, and the droplets that form are surrounded by the channel walls, while in the dripping regime, the shell phase fluid is surrounded by the continuous phase. An increase in continuous-fluid or shell-fluid flow rate leads to dripping to a jetting transition. When three immiscible liquids flow continuously and parallel to one another without dispersing, this is known as laminar flow. In the tubing regime, the core phase flows continuously in the channel's central region, the shell phase flows in the annulus formed by the core phase's central region, and the continuous phase flows between the shell phase fluid and channel walls. In order to discriminate between the aforementioned flow patterns using Weber and Capillary numbers and establish regime transition criteria based on these two dimensionless variables, a flow regime map is provided. Finally, a correlation for shell thickness using shell-to-core phase velocity ratio and conducting 51 CFD simulations was proposed.

Five‐Level Structural Hierarchy: Microfluidically Supported Synthesis of Core–Shell Microparticles Containing Nested Set of Dispersed Metal and Polymer Micro and Nanoparticles

“…The size of microdroplet depends on physical properties and velocity of the carrier, shell, and core phases. [ 25 ] Additionally, the fluid flow and the shape of the emulsion are influenced by the capillary and the Reynolds numbers. [ 26 ] In this study, formed core–shell particles had higher aspect ratios than spherical particles because of the flow conditions.…”

Effects of the microchannel shape upon droplet formations during synthesis of nanoparticles

“…The results show that the ratio of microdroplets to nanoparticles was between 735 and 75. In another study of this group [24], The formation of core/shell microdroplets with uniform size has been investigated numerically in a co-flow microchannel. Finally, they proposed a correlation for the shell thickness using the shell-to-core phase velocity ratio and performed 51 CFD simulations.…”