Numerical simulation of micro-droplet breakup in T-shaped micro-fluidic chip

Three dimensional numerical simulation of micro-droplet breakup in a T-shaped micro-fluidic chip was carried out using the VOF method,and the regimes of breakup and non-breakup were observed,respectively.For a droplet with a specific axial length,there existed a critical capillary number,which could be used to describe the transition between these two regimes.The results showed that micro-droplet would break up when the capillary number was high enough and turned into two daughter droplets.Otherwise non-breakup of droplet would occur while the capillary number was small and micro-droplet would flow into either side of the micro-channel randomly.The correlations between the critical capillary number and the non-dimensional length of micro-droplet were obtained based on numerical simulation.The critical capillary number decreased with increasing droplet size,when the droplet was large enough to obstruct the channel and the pressure accumulated to split the droplet and the critical capillary number was relatively small.When the droplet was too small to obstruct the channel and the pressure was released fast without helping to split the droplet,the critical capillary number was relatively high.Finally,the effect of viscosity ratio on the breakup was discussed and it was found that the higher the viscosity of continuous phase,the higher the capillary number which was needed to break up the droplets,and the critical capillary number decreased with increasing viscosity ratio.