GROWTH-KINETICS AND DOMAIN MORPHOLOGY AFTER OFF-CRITICAL QUENCHES IN A 2-DIMENSIONAL FLUID MODEL

The phase-separation process occurring after an off-critical quench to the unstable region of a two-dimensional Langevin fluid model is studied numerically. Diverse growth kinetics are observed accompanied by distinct domain morphologies depending upon the average value of the order parameter, phi-0, chosen. When phi-0 is near its critical value, the domain morphology is intertwined and the growth kinetics exhibit two time regimes, each with its own growth exponent, similar in behavior to that of the critically quenched fluid. When phi-0 is far from its critical value, the dilute minority phase forms compact clusters and, in contrast to the near critical quench, these clusters grow with only one discernible regime, and the growth exponent n for the time-dependent growth law l(t) approximately t(n) is 0.35 +/- 0.03 in the time regime studied, which is in good agreement with the results of experimental off-critical quenches of fluid mixtures.