FisMat2017 - Submission - View

Abstract's title: Vibrofluidized granular materials: an experimental walk-through
Submitting author: Andrea Puglisi
Affiliation: Istituto dei Sistemi Complessi, CNR
Affiliation Address: ISC-CNR c/o Dipartimento di Fisica, Sapienza Universita' di Roma, p.le A. Moro 2, 00185 Roma
Country: Italy
Oral presentation/Poster (Author's request): Oral presentation
Other authors and affiliations: A. Gnoli, A. Petri, G. Pontuale, A. Sarracino (ISC-CNR, Sapienza, Roma) A. Vulpiani (Dip. Fisica, Sapienza, Roma)

Granular materials are substances made of macroscopic grains. They are ubiquitous in our everyday life and crucial for industry and geophysics. Understanding their statics and dynamics is a challenge for statistical physics, because of their intrinsic non-equilibrium nature. I will discuss a series of recent experimental results obtained within the same setup in different conditions of vibro-fluidization, density and applied external forcing. In the dilute limit, at strong vibro-fluidization, the granular media behaves as a dissipative gas: a probe (a rotator) immersed in the gas experiences random forces, performing a fascinating non-equilibrium Brownian motion, whose properties are fairly predicted by granular kinetic theory. Inelasticity of collisions and solid-on-solid friction affect the probe's dynamics and induce interesting motor ("ratchet") effects. Increasing the density and/or reducing the vibro-fluidization strength, the gas becomes a liquid: collisions become correlated and typical cage effects appear with subdiffusive transient. Surprisingly, at very low "granular temperatures", some new collective phenomena emerges inducing in the probe a pronounced superdiffusive behavior. Another important aspect of a granular media is its response properties. The application of a torque to the probe, by means of an external motor, allows us to verify linear response theory - with all its non-equilibrium effects. Finally, in the non-linear regime, we enter the domain of granular rheology, where we have discovered a discontinuous transition from thinning to thickening regime.

A Gnoli, A Lasanta, A Sarracino, A Puglisi, Scientific Reports 6, 38604 (2016)
C Scalliet, A Gnoli, A Puglisi, A Vulpiani, Physical Review Letters 114, 198001 (2015)
A Gnoli, A Puglisi, A Sarracino, A Vulpiani, PloS one 9, e93720 (2014)
A Gnoli, A Petri, F Dalton, G Pontuale, G Gradenigo, A Sarracino, A. Puglisi, Physical Review Letters 110, 120601 (2013)