Abstract: The simulation on the phase separations of binary fluids with the same and different viscosities has been done and the viscosity effects on the dynamics of phase separations are considered. We found that the domain growth exponent is controlled by the more viscouse phase in the on-critical cases. It reveals that the domain growth at the late stage is dominated by the component with a larger viscosity, which could be used to properly explain some experimental phenomena resulted from the viscosity effects. In off-critical cases, the growth exponent is the characteristic exponent of 1/3. It can be explained by the mechanism of droplet coalescene at the late stage of phase separation in an off-critical binary mixture. It is also demonstrated that in the absence of shear flow, the viscosity difference is not the reason for the inversed phase structure since no inversed phase structure has emerged during the phase separations in our simulation, even if the differences between the two components′ viscosities are very large.

Key words: Phase separation, Viscosity effects, Inversed phase