Clustering and fluidization in a one-dimensional granular system: molecular dynamics and direct-simulation Monte...

Area of Science:

• Physics
• Statistical Mechanics
• Nonlinear Dynamics

Background:

• Granular gases are systems of macroscopic particles interacting through collisions.
• Understanding their behavior is crucial for applications in material science and engineering.
• Previous studies have explored granular gas dynamics, but phase transitions remain an active research area.

Purpose of the Study:

• To investigate the phase behavior of a one-dimensional granular gas confined between two walls at different temperatures.
• To identify the conditions leading to distinct regimes: a completely fluidized state and a state with coexisting clusters.
• To elucidate the underlying mechanism responsible for these observed phase transitions.

Main Methods:

• Simulations of a one-dimensional granular gas of pointlike particles.
• Analysis of system behavior based on the normalized temperature difference (Delta).
• Comparison of Boltzmann equation integration via direct-simulation Monte Carlo (DSMC) with Newtonian molecular dynamics.

Main Results:

• Two distinct regimes were observed: a completely fluidized state and a state where a cluster coexists with the fluidized gas.
• Cluster formation is inhibited above a critical normalized temperature difference (Delta).
• The fluidized state exhibits non-Gaussian velocity distribution functions.

Conclusions:

• The normalized temperature difference is the key parameter governing the phase behavior of this granular gas system.
• The observed non-Gaussian features in the fluidized state are not due to particle correlations, as validated by DSMC and molecular dynamics simulations.
• The study provides a mechanistic explanation for the emergence of distinct phases in confined granular gases.