Segregation in a fluidized binary granular mixture: Competition between buoyancy and geometric forces

TL;DR

This paper develops a hydrodynamic model for binary granular mixtures to explain Brazil-nut segregation as a competition between buoyancy and geometric forces, influenced by inelastic dissipation.

Contribution

It introduces a coupled evolution equation for intruder velocity derived from hydrodynamics, highlighting the roles of buoyancy and geometric forces in segregation.

Findings

Model explains experimental segregation patterns.

Inelastic dissipation significantly alters phase diagrams.

Theoretical results align with Breu et al.'s experimental data.

Abstract

Starting from the hydrodynamic equations of binary granular mixtures, we derive an evolution equation for the relative velocity of the intruders, which is shown to be coupled to the inertia of the smaller particles. The onset of Brazil-nut segregation is explained as a competition between the buoyancy and geometric forces: the Archimedean buoyancy force, a buoyancy force due to the difference between the energies of two granular species, and two geometric forces, one compressive and the other-one tensile in nature, due to the size-difference. We show that inelastic dissipation strongly affects the phase diagram of the Brazil nut phenomenon and our model is able to explain the experimental results of Breu et al. (PRL, 2003, vol. 90, p. 01402).