Phase transitions are ubiquitous in nature, boiling water, metal-alloy transition,
and ferromagnetic transitions, to mention a few. Recently, it has been shown
that a fluidized granular system in two spatial dimensions with a vibrating wall
and without gravity exhibits rich and complex dynamics at phase separation (Argentina, Clerc & Soto, 2002). The mechanism of this phase separation is
triggered by a negative compressibility implied by the fact that the granular
temperature is a decreasing function of the density for a fixed geometry and
boundary conditions. Molecular dynamics simulations of a grain system at the
onset of phase transition reveal rich dynamical behavior characterized by
appearance, coalescence, and disappearance of bubbles. When the granular
viscosity is small, the coarsening dynamics exhibited by the bubbles is<
mediated by nonlinear waves.
It will be therefore very interesting to observe experimentally and to study
theoretically such rich dynamic behaviors. A granular system seems a natural
candidate, although it seems technically difficult to achieve such detailed
measurements (acoustic pressure, density measurements, etc). Another
candidate is the phase transition at the liquid-vapor critical point, in confined
geometry. Taking as a start point the solid-liquid phase coexistence observed
in a vertically vibrated granular monolayer (Urbach, et al. 2004 & 2005) we have
started a joint effort to study this system experimentally, numerically and
theoretically. Our preliminary results indicate that this system indeed shows a
spinodal decomposition analogue to the liquid-vapor separation observed in
the van der Waals gas model.
References
- "van der Waals-Like Transition in Fluidized Granular Matter", M. Argentina
M.G. Clerc, & R. Soto, Phys Rev Lett. vol. 89 044301 (2002).
- "Non-equilibrium two-phase coexistence in a confined granular layer", A.
Prevost, P. Melby, D. A. Egolf, & J. S. Urbach, Phys. Rev. E, Rapid
Communication, Vol. 70, 050301(R) (2004).
- "The dynamics of thin vibrated granular layers", P. Melby, F. Vega Reyes, A.
Prevost, R. Robertson, P. Kumar, D. A. Egolf, & J. S. Urbach, J. Phys. Cond.
Mat. vol. 17, S2689-S2704 (2005).
People involved:
Germán Varas (Universidad de Chile)
Cristian Gonzalez (Universidad de Chile)
Dino Risso (Universidad del Bío-Bío)
Patricio Cordero (Universidad de Chile)
Marcel Clerc (Universidad de Chile)
Nicolás Mujica (Universidad de Chile)
