Sudden chain energy transfer events in vibrated granular media

TL;DR

This paper investigates sudden energy transfer events in vibrated granular media, revealing how chain reactions among heavy particles cause abrupt energy peaks and influence segregation dynamics.

Contribution

It introduces a new explanation for energy bursts in granular mixtures based on chain reactions and fixed points in particle bouncing behavior.

Findings

Energy peaks correlate with cluster expansion and segregation loss.

Chain reactions among heavy particles trigger sudden energy transfers.

Regularity of events depends on the extent of chain reactions.

Abstract

In a mixture of two species of grains of equal size but different mass, placed in a vertically vibrated shallow box, there is spontaneous segregation. Once the system is at least partly segregated and clusters of the heavy particles have formed, there are sudden peaks of the horizontal kinetic energy of the heavy particles, that is otherwise small. Together with the energy peaks the clusters rapidly expand and the segregation is partially lost. The process repeats once segregation has taken place again. Depending on the experimental or numerical parameters, the energy bursts can occur either randomly or with some regularity in time. An explanation for these events is provided based on the existence of a fixed point for an isolated particle bouncing with only vertical motion. The horizontal energy peaks occur when the energy stored in the vertical motion is partly transferred into horizontal energy through a chain reaction of collisions between heavy particles. A necessary condition for the observed regularity of the events is that chain reactions involve most of the heavy particles.