Micro-droplet formation in the crossing micro-channel was numerically simulated by the 3D VOF model. Three flow regimes to generate droplet with monodispersity (squeezing

dripping and jetting) and other regimes (turbulent jetting

nodular flow

tubular flow

slip flow) were obtained. The simulation results agreed well with experiment observations

which validated the numerical model. The flow regimes were mainly affected by flow rate

surface tension and viscosity of two phases. With increasing flow rate of the continuous phase

droplet size would decrease and generation frequency would increase

whereas the effect of flow rate of the disperse phase was the opposite. Surface tension and viscosity of the continuous phase played a leading role under the conditions of high and low Ca number of the continuous phase

respectively. When Ca number was low

droplet size decreased in the squeezing and dripping regimes and increased in the jetting regime with decreasing surface tension

while generation frequency shows the reverse changing tendency compared with droplet size. When Ca number of the continuous phase was high

however

droplet size decreased with increasing the viscosity of the continuous phase

while generation frequency changed inversely. In addition

contact angel had little effect on the squeezing regime

but droplet could not be generated in the dripping and jetting regimes when contact angel decreased.