Nonequilibrium two-phase coexistence in a confined granular layer

Abstract

We report the observation of the homogenous nucleation of crystals in a dense layer of steel spheres confined between two horizontal plates vibrated vertically. Above a critical vibration amplitude, two-layer crystals with square symmetry were found to coexist in steady state with a surrounding granular liquid. By analogy to equilibrium hard-sphere systems, the phase behavior may be explained through entropy maximization. However, dramatic nonequilibrium effects are present, including a significant difference in the granular temperatures of the two phases.

Patterns and collective behavior in granular media: Theoretical concepts

“…Nie et al (2000); Prevost et al (2004) reproduced certain features of cluster formation and two-phase co-existence by means of large-scale three-dimensional molecular dynamics simulations. Since realistic threedimensional simulations are still expensive and extremely time-consuming, simplified modelling of the effect of a vibrating wall by a certain multiplicative random forcing on individual particles was employed by Cafiero et al (1999).…”

“…The experiments (Losert et al, 1999;Olafsen and Urbach, 1998;Prevost et al, 2004; demonstrated emergence and growth of multiple clusters but did not have sufficient aspect ratio to address the problem of coarsening in a quantitative way.…”

“…solidification fronts in supercooled liquids. Prevost et al (2004) performed experiments with vibrated granular gas confined between two plates. Qualitatively similar phase coexistence was found.…”

“…Lois et al (2005); Radjai et al (1998); Staron et al (2002) applied contact dynamics methods and Silbert et al (2002a,b); Volfson et al (2003a,b) used soft-particles technique for the analysis of instabilities and constitutive relations in dense granular systems. Patterns in vibrated layers were studied by event-driven simulations by Bizon et al (1998a); Moon et al (2003) and by soft particles molecular dynamics simulations by Nie et al (2000); Prevost et al (2004).…”

“…Nishimori and Ouchi (1993) FIG. 42 Interaction and coarsening of one-dimensional dune system, from Prigozhin (1999) In the continuum description of the evolution of the sand surface, the profile h is governed by the mass conservation equation…”