Morphology and Dynamics of Phase‐Separating Fluids with Viscosity Asymmetry

Abstract

AbstractSummary: The effects of viscosity asymmetry of the components on morphology and dynamics of phase‐separating AB fluids are investigated numerically based on a modified Model H. For critical mixtures, in the early stage of phase separation the co‐continuous morphology with droplets of A in B and B in A is observed. In the late stage of phase separation, the viscosity asymmetry leads to morphological change from co‐continuous structure to completely dispersed structure where the less viscous component forms droplet. The pathway of this transformation is accompanied by the breakdown of balance of volume fraction between droplets with different viscosity. Domain growth is characterized by a crossover from a faster growth at intermediate time under the influence of hydrodynamics to Lifshitz–Slyozov behavior at late times. For off‐critical mixture, viscosity asymmetry only plays an important role for domain growth in the intermediate stage of phase separation and the domain growth depends on whether the more viscous phase is dispersed or continuous, and the late stage of domain growth follows Lifshitz–Slyozov power law independent of which phase is dispersed.Result for the evolution of phase‐separating domains for critical fluid mixtures $\bar \phi _A$ = 0.5 for t = 1 500 with viscosity asymmetry: ηA = 0.8, ηB = 0.2. A‐rich regions and B‐rich regions are represented by white and black, respectively.imageResult for the evolution of phase‐separating domains for critical fluid mixtures $\bar \phi _A$ = 0.5 for t = 1 500 with viscosity asymmetry: ηA = 0.8, ηB = 0.2. A‐rich regions and B‐rich regions are represented by white and black, respectively.