A Simple Method to Mix Granular Materials

TL;DR

This paper demonstrates how granular temperature gradients and gravity can be manipulated to control mixing and segregation of granular particles with equal sizes but different densities, providing practical guidelines for achieving uniform mixtures.

Contribution

It introduces a simple method to control granular mixing and segregation by adjusting temperature gradients and gravity, with a relation linking container height, particle properties, and gravity strength.

Findings

Dense particles move to colder regions without gravity.

Gravity with colder regions above can produce uniform mixtures.

Derived relation for container height and gravity to minimize segregation.

Abstract

We show that a mixture of two species of granular particles with equal sizes but differing densities can be either segregated or mixed by adjusting the granular temperature gradient and the magnitude of the gravitational force. In the absence of gravity, the dense, heavy particles move to the colder regions. If the temperature gradient is put into a gravitational field with the colder regions above the hotter, a uniform mixture of light and heavy particles can be attained. This situation can be realized in a container of finite height with a vibrating bottom, placed in a gravitational field. We present a relation between the height of the container, the particle properties, and the strength of gravity required to minimize segregation.