Spinodal decomposition of a binary fluid with fixed impurities

The phase separation dynamics of a binary fluid containing randomly distributed fixed impurities is studied in two dimensions (d=2). The impurities act as osmotic force centers and favor one component of the fluid. We found, as expected, that hydrodynamic flow promotes the coalescence of the domains in the early stage of phase separation; at later stages for sufficiently high particle density and strong preferential interaction strength, the domain growth slows down and finally is pinned at a finite domain size independent of the hydrodynamics. The density of impurities in the unfavorable phase is shown to satisfy a scaling form involving the total impurity density n0 and the ratio R/R0 with R the domain size and R0=n0−1/d the average distance between the impurities.