Experiments in randomly agitated granular assemblies close to the jamming transition

TL;DR

This paper reports preliminary experimental results on granular assemblies near the jamming transition, exploring novel shaking methods and their effects on microscopic and macroscopic properties, including effective temperature and fluctuation relations.

Contribution

Introduces a new shaking technique for granular systems and investigates their microscopic dynamics and effective temperature near jamming transition.

Findings

Large scale dynamics influence transport properties.

New vibration method allows controlled random accelerations.

Initial results on surface evolution and fluctuation relations.

Abstract

We present here the preliminary results obtained for two experiments on randomly agitated granular assemblies using a novel way of shaking. First we discuss the transport properties of a 2D model system undergoing classical shaking that show the importance of large scale dynamics for this type of agitation and offer a local view of the microscopic motions of a grain. We then develop a new way of vibrating the system allowing for random accelerations smaller than gravity. Using this method we study the evolution of the free surface as well as results from a light scattering method for a 3D model system. The final aim of these experiments is to investigate the ideas of effective temperature on the one hand as a function of inherent states and on the other hand using fluctuation dissipation relations.