HYDRODYNAMIC EFFECTS IN PHASE-SEPARATION - AN EXPLICIT SOLUTION APPROACH

We study the influence of hydrodynamic modes on phase separation by mo deling pure-phase domains with kinks. The velocity field, determined a diabatically in terms of the thermodynamic source, describes a steady state compressible flow. We consider spherical, columnar, and disklike domains. In the former two cases, we obtain crossover from the (R) ov er dot similar to 1/R-2 law to the R similar to t law as in the incomp ressible case. The growth of columnar domains is dominated by hydrodyn amics, while for spherical domains we find competition between hydrody namics and particle diffusion: this competition determines a threshold in size for the fluctuations, i.e., only large enough fluctuations ca n initiate the spinodal decomposition. We finally study disklike domai ns in a quasi-two-dimensional system and obtain, for small radii, the growth law (R) over dot similar to 1/[R(3)ln(Lambda/R)], while for lar ge radii (R) over dot similar to 1/[R(2)ln(Lambda/R)]. We find that st able microdomains can be formed, whose size is fixed by the thickness of the lamella and by the parameters of the fluid (e.g., viscosity, tr ansport coefficient, etc.).