A note on the upward and downward intruder segregation in granular media

TL;DR

This paper presents a hydrodynamic model explaining how size and density differences cause intruder particles to segregate upward or downward in vibrated granular media, highlighting a buoyant force mechanism.

Contribution

It introduces a density-based segregation mechanism and analytically describes the transition between upward and downward movement of intruders.

Findings

Segregation depends on density differences and vibrational conditions.

A transition from upward to downward movement is analytically derived.

Buoyant force explains the segregation behavior.

Abstract

The intruder segregation dependence on size and density is investigated in the framework of a hydrodynamic theoretical model for vibrated granular media. We propose a segregation mechanism based on the difference of densities between different regions of the granular system, which give origin to a buoyant force that acts on the intruder. From the analytic solution of the segregation velocity we can analyze the transition from the upward to downward intruder's movement.