Time Dependence and Density Inversion in Simulations of Vertically Oscillated Granular Layers

TL;DR

This paper investigates the behavior of granular layers under vertical oscillation, revealing a steady-state density inversion at high amplitudes and oscillatory behavior at low amplitudes, with continuum and molecular dynamics simulations showing consistent results.

Contribution

It demonstrates that continuum simulations can accurately replicate molecular dynamics results in modeling oscillated granular layers, including density inversion phenomena.

Findings

Density inversion occurs at high oscillation amplitudes.

Layer exhibits oscillatory behavior at low amplitudes.

Continuum and molecular dynamics simulations agree.

Abstract

We study a layer of grains atop a plate which oscillates sinusoidally in the direction of gravity, using three-dimensional, time-dependent numerical solutions of continuum equations to Navier-Stokes order as well as hard-sphere molecular dynamics simulations. For high accelerational amplitudes of the plate, the layer exhibits a steady-state "density inversion" in which a high-density portion of the layer is supported by a lower-density portion. At low accelerational amplitudes, the layer exhibits oscillatory time dependence that is strongly correlated to the motion of the plate. We show that continuum simulations yield results consistent with molecular dynamics results in both regimes.