Why Granular Media Are, After All, Thermal

TL;DR

This paper explores the thermal properties of granular media, arguing that despite their macroscopic size, thermal effects within grains influence their behavior and should be included in models.

Contribution

It provides a comprehensive analysis of thermal versus athermal descriptions of granular media, highlighting the importance of internal thermal degrees of freedom.

Findings

Granular media exhibit internal thermal fluctuations.

Thermal expansion affects granular dynamics.

Including thermal effects improves modeling accuracy.

Abstract

Granular media are considered "athermal", because the grains are too large to display Brownian type thermal fluctuations. Yet being macroscopic, every grain undergoes thermal expansion, possesses a temperature that may be measured with a thermometer, and consists of many, many internal degrees of freedom that in their sum do affect granular dynamics. Therefore, including them in a comprehensive approach to account for granular behavior entails crucial advantages. The pros and cons of thermal versus athermal descriptions are considered.