Numerical study of the dynamics of a droplet in a T-junction microchannel using OpenFOAM

Abstract

The mechanisms of droplet breakup in a Microfluidic T-junction are mainly influenced by the capillary number Ca and the ratio between the length of the droplet and the transverse dimension of the microchannel (lo/w). This work presents numerical simulations of an isolated Taylor droplet in a rectangular T-junction microchannel in the range of 0.0096 to 0.0904 of capillary numbers and viscosity ratio of the dispersed and continuous phases, that is, μd/μc=0.125. The numerical simulations were carried out with OpenFOAM 2.4 by using the S-CLSVOF methodology which was implemented for this study. The snappyHexMesh tool was used for grid refinement near the microchannel wall in order to correctly model the thin fluid layer between the wall and the drop. It was verified that in this range of the capillary numbers, parasitic currents could affect the dynamics of the droplet in the microchannel. The use of S-CLSVOF, the time step control and mesh resolution enabled a better capture of the interface dynamics. A mathematical correlation was obtained in the obstructed breakup regime for the dimensionless thickness of the droplet (δ/w) in relation to Ca, dimensionless time (τ∗=Udt/w) and droplet length (lo/w). Two types of non-obstructed breakup were observed in the simulations, namely, partially obstructed, and with permanent tunnel. The results showed that the mechanisms of a droplet breakup inside a T-junction are in good agreement with literature.