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

摘要

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