The minimization of mechanical work in vibrated granular matter.

James P D Clewett,Jack Wade,R M Bowley,Michael R Swift,Marco G Mazza,Stephan Herminghaus

doi:10.1038/srep28726

James P D Clewett, Jack Wade + Show 4 more

Open Access

https://doi.org/10.1038/srep28726

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Abstract

Experiments and computer simulations are carried out to investigate phase separation in a granular gas under vibration. The densities of the dilute and the dense phase are found to follow a lever rule and obey an equation of state. Here we show that the Maxwell equal-areas construction predicts the coexisting pressure and binodal densities remarkably well, even though the system is far from thermal equilibrium. This construction can be linked to the minimization of mechanical work associated with density fluctuations without invoking any concept related to equilibrium-like free energies.

Highlights

Experiments and computer simulations are carried out to investigate phase separation in a granular gas under vibration
Inspired by analogous problems in equilibrium thermodynamics, it has proven useful to study non-equilibrium steady states (NESS) which are characterized by time-independent, non-trivial macroscopic quantities, such as the pressure and densities in a phase separated system
We study a system of approximately monodisperse spheres with diameter d = 610 μm, confined between two horizontal plates separated by a distance of 10 mm, and driven vertically by a sinusoidal motion with amplitude A

Summary

Introduction

Experiments and computer simulations are carried out to investigate phase separation in a granular gas under vibration. Away from the elastic limit its behaviour is expected to differ, since some basic assumptions of equilibrium statistical physics, such as detailed balance, are no longer valid We investigate both experimentally and by computer simulations the phase separation behaviour of driven granular gases far away from the elastic limit, down to ε = 0.65. We demonstrate that can a Maxwell equal-areas construction predict the coexistence pressure and binodal densities remarkably well, but that such a construction can be applied, with reasonable accuracy, away from the critical point and for high dissipation We argue that this construction can be traced to the minimisation of mechanical work associated with density fluctuations. The deviations from an exact Maxwell construction are small, we show their significance and provide a tentative interpretation

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