3D numerical simulation of droplet passive breakup in a micro-channel T-junction using the Volume-Of-Fluid method

Abstract

A 3D simulation was conducted using the Volume-Of-Fluid (VOF) method to reveal the breakup mechanism of micro-droplets in a micro-channel T-junction. This simulation was validated by a flow visualization experiment, in which two T-shaped junctions with a 200 μm × 100 μm cross-section were connected for droplet generation and breakup. Four flow patterns of micro-droplets were observed by numerical simulation and experiment observation, namely, breakup with tunnel, breakup with discontinuous obstruction, breakup with permanent obstruction, and non-breakup (NB). The breakup and NB of droplets depend mainly on the relative dominance of surface tension represented in the Capillary number and relative droplet length. A critical capillary number was used to distinguish the breakup and NB regimes. The droplet size became highly linear in the breakup regimes, and a critical droplet neck based on the classical Rayleigh-Plateau instability was used to describe the droplets breakup regimes. An empirical correlation to illustrate the development of droplet sizes with the dimensionless time in the breakup regime with permanent obstruction was proposed to predict the droplet size. Results were consistent with the numerical simulation.