Phase separation dynamics of ternary system with and without shear: a Lattice Boltzmann Method approach

Abstract

Ternary phase separation plays a crucial role in understanding the complex behavior of multi-component fluid mixtures, particularly under varying flow conditions. This study investigates the phase separation dynamics of ternary fluid mixtures under both quiescent and sheared conditions using a free-energy Lattice Boltzmann Method. In the absence of shear, domain growth and final morphologies are characterized for different volume fraction configurations across a range of values of the intrinsic fluidity parameter, defined as the ratio between peclet and capillary number. ☐ When a ternary mixture subjected to shear flow undergoes phase separation, the resulting morphology is governed by two competing effects: the natural coarsening of domains and shear-induced deformation. While domains tend to grow over time, the applied shear stretches them along the flow direction, leading to unique morphologies. Our results for an intermediate shear regime (applied shear is insufficient to induce strongly anisotropic or fully aligned structures), reveal that at low capillary numbers, the system reaches a periodic steady state featuring complex droplet morphologies such as double emulsions and worm-like structures. In contrast, at high capillary numbers, phase separation results in banded structures extended along the shear direction. Under inertialess conditions, we find that the phase separation dynamics are primarily governed by capillary number, and appear to be largely independent of the components' volume fractions. This contrasts with the no-shear case, where the final morphologies are strongly dependent on the volume fractions. ☐ The range of morphologies predicted under both quiescent and sheared conditions demonstrates the potential of this research for applications in the design and manufacturing of polymeric and soft materials.