Lattice Boltzmann simulation of phase separation under dynamic temperature and shear: Coupling effects of shear convection and thermal diffusion.

Abstract

This paper presents an exploration of the separation behavior and pattern formation in a shear binary fluid with dynamic temperature after slow cooling via coupled lattice Boltzmann method. The phase separation procedure can be divided into three different stages: spinodal decomposition, domain growth, and domain stretch. The effect of thermal diffusion was observed to be more significant than that of shear convection in the spinodal decomposition stage, while the opposite was observed in the domain growth stage. The slow cooling temperature field significantly prolonged the spinodal decomposition stage, and decreased the separated domain size in domain growth stage. The phase behavior and pattern formation from the disordered state into the coexistence state after slow cooling was investigated during the domain stretch stage. Two typical length scales were obtained according to the equilibrium of two phases, where the number of layers in the corresponding domains was controllable by adjusting the Prandtl number for systems of different scales. The manner in which various viscosities and thermal diffusivities influence the morphologies and kinetic characterizations of the materials was also demonstrated: numerical results indicated that decrease in viscosity can cause increase in the growth exponents of separation fronts and velocity of domain growth, as well as increase in thermal diffusion.