Simultaneous effects of capillary number, viscosity ratio, and contraction ratio on droplet dynamics in contraction microchannel

In microfluidic systems utilized droplets, fluid properties, flow conditions, and channel geometry play crucial roles in the movement and manipulation of droplets. This study employs methods of theoretical modeling and three-dimensional numerical simulation to investigate droplet dynamics in a contraction microchannel under the simultaneous influence of different factors, such as capillary number ( Ca ), viscosity ratio ( λ ), and contraction ratio ( C ). Specifically, a theoretical model is introduced for predicting the transition of droplets from trap to squeeze, and it is observed to be C a I = f ( C , λ ) . Meanwhile, droplet dynamics are investigated for the transition from squeeze to breakup for finding critical capillary number value (Ca II ). In addition, the critical viscosity ratio for the process from squeeze to breakup has been figured out by numerical results for a wide range of contraction ratios. Eventually, droplet dynamics including deformation, velocity ratio, and breakup during contraction microchannel are also quantitatively studied under the factors above.