Self-charging of identical grains in the absence of an external field

TL;DR

This paper explores how identical grains can self-charge rapidly without external fields, using simulations, mathematical modeling, and experiments, revealing exponential growth and novel states in microgravity conditions.

Contribution

It introduces a mathematical Turing model explaining self-charging mechanisms and validates exponential growth predictions through experiments with vibrated grains in microgravity.

Findings

Infinitesimal initial charges grow exponentially rapidly.

Mathematical Turing model predicts conditions for exponential charging.

Experimental confirmation of exponential growth in microgravity.

Abstract

We investigate the electrostatic charging of an agitated bed of identical grains using simulations, mathematical modeling, and experiments. We simulate charging with a discrete-element model including electrical multipoles and find that infinitesimally small initial charges can grow exponentially rapidly. We propose a mathematical Turing model that defines conditions for exponential charging to occur and provides insights into the mechanisms involved. Finally, we confirm the predicted exponential growth in experiments using vibrated grains under microgravity, and we describe novel predicted spatiotemporal states that merit further study.