Experimental evidence for a description of granular segregation in terms of the effective temperature

Abstract

Granular segregation, spontaneous demixing of components in flowing mixtures, is a phenomenon of practical importance and occurs in a number of natural systems. We present a model to describe granular segregation due to density differences in a dense granular flow. Such flows are a prototype of "jammed" systems for which a new thermodynamics has been proposed arising from analysis of glassy systems and packed powders. In the context of this new framework, we show that granular segregation is determined by the effective temperature defined by the fluctuation-dissipation relation. The description has no fitted parameters and is validated by experiments. The work shows the utility of the effective temperature for the analysis of transport in granular flows and indicates the promise of the new thermodynamics for the description of practical systems.