Simulation of Single Droplet Deformation and Breakup in Shear Flow by the Phase-Field Lattice Boltzmann Method

The deformation and breakup of droplets, which affect droplet size and their size distributions, are of great significance in liquid–liquid two-phase systems. However, the understanding of deformation and breakup for droplets is still limited. In this work, the dynamic behavior of a single droplet under laminar shear flow was investigated by the phase-field lattice Boltzmann method. The effects of the capillary number, Reynolds number, wall confinement, droplet diameter, and viscosity ratio on droplet deformation and breakup were systematically studied. Numerical results found that the same capillary number led to different droplet breakups; thus, another important criterion, the dynamic pressure exerted on droplets, should be considered and quantitatively calculated. The compromise-in-competition between dynamic pressure and cohesive stresses in droplet breakup was thoroughly considered. It was found that droplets tend to break up more rapidly when dynamic pressure significantly exceeds cohesive stresses, which agreed well with the simulated results by the phase-field lattice Boltzmann model.