Energy partition and segregation for an intruder in a vibrated granular system under gravity

TL;DR

This paper investigates how an impurity's temperature compares to the surrounding granular gas in a vibrated system under gravity, revealing constant temperature ratios in the bulk and linking energy non-equipartition to segregation behavior.

Contribution

It introduces a theoretical framework connecting temperature ratios, pressure diffusion, and segregation in vibrated granular systems, validated by experiments and simulations.

Findings

Temperature ratio remains constant in the bulk despite inhomogeneity.

Segregation is linked to the change of sign in the pressure diffusion coefficient.

Theoretical predictions align with experimental and simulation results.

Abstract

The difference of temperatures between an impurity and the surrounding gas in an open vibrated granular system is studied. It is shown that, in spite of the high inhomogeneity of the state, the temperature ratio remains constant in the bulk of the system. The lack of energy equipartition is associated to the change of sign of the pressure diffusion coefficient for the impurity at certain values of the parameters of the system, leading to a segregation criterium. The theoretical predictions are consistent with previous experimental results, and also in agreement with molecular dynamics simulation results reported in this paper.