Competition of Brazil nut effect, buoyancy, and inelasticity induced segregation in a granular mixture

TL;DR

This paper investigates how inelasticity, buoyancy, and size differences compete to cause segregation in granular mixtures, revealing a transition line that determines the dominant mechanism and conditions for coexistence of effects.

Contribution

It provides a detailed numerical analysis of the competition between multiple segregation mechanisms in granular mixtures, identifying transition conditions and coexistence regimes.

Findings

Inelasticity can cause particles to sink, competing with buoyancy and Brazil nut effects.

A transition line in parameter space determines the dominant segregation mechanism.

Coexistence of BNE and RBNE occurs at intermediate inelasticities, with particles segregating both at top and bottom.

Abstract

It has been recently reported that a granular mixture in which grains differ in their restitution coefficients presents segregation: the more inelastic particles sink to the bottom. When other segregation mechanisms as buoyancy and the Brazil nut effect are present, the inelasticity induced segregation can compete with them. First, a detailed analysis, based on numerical simulations of two dimensional systems, of the competition between buoyancy and the inelasticity induced segregation is presented, finding that there is a transition line in the parameter space that determines which mechanism is dominant. In the case of neutrally buoyant particles having different sizes the inelasticity induced segregation can compete with the Brazil nut effect (BNE). Reverse Brazil nut effect (RBNE) could be obtained at large inelasticities of the intruder. At intermediate values, BNE and RBNE coexist and large inelastic particles are found both near the bottom and at the top of the system.