98-593 S. Bastea, J. L. Lebowitz

Spinodal Decomposition in Binary Gases (112K, ReVTeX) Sep 9, 98

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Abstract. We carried out three-dimensional simulations, with about $1.4\times10^6$ particles, of phase segregation in a low density binary fluid mixture, described mesoscopically by energy and momentum conserving Boltzmann-Vlasov equations. Using a combination of Direct Simulation Monte Carlo(DSMC) for the short range collisions and a version of Particle-In-Cell(PIC) evolution for the smooth long range interaction, we found dynamical scaling after the ratio of the interface thickness(whose shape is described approximately by a hyperbolic tangent profile) to the domain size is less than $\sim0.1$. The scaling length $R(t)$ grows at late times like $t^\alpha$, with $\alpha=1$ for critical quenches and $\alpha=\frac{1}{3}$ for off-critical ones. We also measured the variation of temperature, total particle density and hydrodynamic velocity during the segregation process.

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