Droplet generation hydrodynamics in the microfluidic cross-junction with different junction angles

A 3D numerical study is performed to investigate the hydrodynamics of droplet generation in microfluidic cross-junctions with different junction angles theta. Four flow regimes during droplet generation are identified, namely squeezing, dripping, jetting and threading, and the regime diagrams are plotted to represent them. Droplet generation performance changes with the flow regime, especially when theta deviates from 90 degrees. In addition, variation in theta changes the hydrodynamic characteristics in and around the cross-junction region, which can affect its interface profile and evolution. However, it is insufficient to fundamentally alter the flow regimes under the current conditions. Considering the length of the dispersed phase entering and blocking the main channel of the cross-junction, as well as the influence of theta on the hydrodynamics of droplet generation, a scaling correlation is developed to predict the size of the generated droplets under the squeezing regime in the microfluidic cross-junction. (C) 2019 Elsevier Ltd. All rights reserved.