Numerical investigation on formation mechanism and flow law of droplet in T-junction by electric field

The mechanism of constant electric field regulation on droplet formation in a T-junction microchannel is investigated numerically, and the law of discrete phase fluid behavior in different viscosity systems is summarized. This research develops a two-phase-electrohydrodynamic solver in the OpenFOAM® framework. The solver uses a leaky medium model to simulate the microfluidic system and uses the volume of fluid method to trace the phase interface. It is found that the mechanism of droplet generation within the microfluidic system can be divided into squeeze and shear effect, where the shear mechanism will have transition to the squeeze mechanism under the influence of the electric field. Additionally, the effect of the electric field on the discrete phase fluid is significantly influenced by the viscosity of the continuous phase fluid. At low to medium viscosity, droplet length can be affected by wall shear resistance and undergo sudden changes at a certain electric field strength, but the mutation will decrease to disappear with the increase in the system viscosity. At high viscosity, droplets undergo significant agglomeration in the interaction of electric field force and viscous shear. Then, the regulating mechanism of constant electric field on a discrete phase fluid flow pattern in an ultra-high viscosity system is also studied. Finally, a map is proposed that adequately describes the variation of discrete phase fluid behavior with constant electric field strength with different continuous phase fluid viscosities.