Asymmetric droplet splitting in a T-junction under a pressure difference

Abstract

In this paper, the phase-field multiphase lattice Boltzmann method is employed to simulate droplet breakup in a T-junction under different outlet pressures. Three behaviors of droplet breakup: non-breakup (flow pattern I), breakup with tunnels (flow pattern II), and breakup with permanent obstruction (flow pattern Ⅲ) are identified. The evolution of morphological characteristics of droplet breakup is quantitatively characterized, based on which the asymmetric splitting mechanisms and the influencing factors are clarified. Additionally, the factors influencing the droplet splitting volume ratio (V_II/V_I) are elucidated. The results indicate that there is a non-linear relationship between the V_II/V_I and the flow rate ratio. Moreover, the curve depicting the final V_II/V_I versus the initial droplet length exhibits a V-shape and has a minimum value. A conclusion is drawn that the Capillary number mainly influences flow pattern II, with the final V_II/V_I decreasing as the Capillary number increases. Additionally, for flow pattern III, the final V_II/V_I increases linearly with rising droplet size at low viscosity ratios, whereas it decreases linearly at high viscosity ratios. The growing outlet pressure difference enlarges the flow difference between the two branches, leading to an increase in the final V_II/V_I.