Droplet breakup through triangular obstacle in T-junction microchannel

This paper investigates the breakup of droplets in a T-junction microchannel, enhanced by the strategic placement of an isosceles triangular obstacle. Numerical simulations using the phase field method reveal that the breakup of primary droplets is mainly influenced by shear force, pressure drop, wall contact angle, and obstacle position. It is found that the droplet exhibits three distinct states: breakup, non-breakup, and merge after breakup. The results show that wall wettability affects droplet morphology and velocity but has a minor impact on breakup. The breakup modes and volume ratio of daughter droplets depend on the obstacle position. The non-dimensional radial positions (d), defined as the dimensionless length from the obstacle tip to the lower channel wall, result in the formation of two daughter droplets when within ranges such as 0.375 < d < 0.475 and 0.5 < d < 0.575. At d < 0.5, the dimensionless droplet length decreases from 0.8 to 0.6, while stabilizing around 0.75 for d > 0.5. Smaller dimensionless axial positions (x3), defined as the dimensionless length from the obstacle tip to the channel inlet, leading to more complex breakup behaviors. Compared to wall wettability and obstacle position, obstacle size has minimal impact on breakup but significantly increases pressure drop. Finally, the critical capillary number (Cacr) varies nonlinearly with changes in the parameters, where d has a significant influence on Cacr curve in comparison with other parameters.