Title: First Order Phase Transition and the Simulation of a Quasi 2D Granular Fluid

Author (Poster): Jiaju Ma, ccny

Abstract:

We simulate vibrated granular materials in a variety of situations. In particular, we investigate the solid-fluid phase transitions in a non-equilibrium system, a vertically vibrated quasi-2d granular fluid under isobaric conditions. Experiments show that a transition occurs between a gas and a crystal as a function of the driving strength. The phase transition is of first-order, characterized by a discontinuous change in both density and temperature. The transition also shows rate-dependent hysteresis, which disappears for sufficiently slow heating. We have performed simulations of this first-order phase transition by using soft sphere molecular dynamics with a constant time step and second order Velocity Verlet algorithm. We limit ourselves to the case of non-cohesive, dry, spherical grains. A three dimensional setup has been carried out to simulate the quasi-2d experiment. The simulation results show a hysteretic phase transition which compares well with the experiment. In general, the results of our experimental study and the simulation provide a better understanding of the specifics of phase transition in granular fluids.