Numerical Study of Symmetric and Asymmetric T-Junctions Droplet Formation

In this paper, the flow regime of the fluid and the dynamic process of droplet formation in an asymmetric T-junction were investigated by numerical simulation based on the phase field method. The results show that the asymmetric structure significantly changes the flow characteristics of the droplets. With the decrease of width ratio, the region of dripping and squeezing is significantly enlarged, and the range of controllable droplet formation is also enhanced, during the squeezing regime, compared with the symmetric structure. The upstream pressure of the T-junction with a low width ratio increases. Within the dripping regime, the abrupt change in the structure raises the velocity of the continuous phase, which leads to the enhancement of viscous forces acting on the dispersed phase, thereby significantly improving the droplet separation efficiency. In addition, changes in the viscosity ratio promote the transition to the jetting regime in the T-junction under dripping conditions, but the accelerating effect of the small channel is more capable of resisting this effect. Furthermore, surface wettability also plays an important role in droplet formation.