Cooling and aggregation in wet granulates

TL;DR

This paper investigates the cooling and aggregation processes in wet granular materials, revealing a nonequilibrium transition, self-similar cluster growth, and fractal structures, supported by scaling analysis and simulations.

Contribution

It introduces a scaling framework for understanding bond-breaking, aggregation, and gelation in wet granular systems, supported by simulation validation.

Findings

Identification of a nonequilibrium transition at bond energy threshold

Self-similar cluster growth with scaling laws

Observation of fractal clusters with D_f=2 and gelation

Abstract

Wet granular materials are characterized by a defined bond energy in their particle interaction such that breaking a bond implies an irreversible loss of a fixed amount of energy. Associated with the bond energy is a nonequilibrium transition, setting in as the granular temperature falls below the bond energy. The subsequent aggregation of particles into clusters is shown to be a self-similar growth process with a cluster size distribution that obeys scaling. In the early phase of aggregation the clusters are fractals with D_f=2, for later times we observe gelation. We use simple scaling arguments to derive the temperature decay in the early and late stages of cooling and verify our results with event-driven simulations.