Levich Institute Seminar Announcement, 03/28/2006
Steinman Hall, Room #312
(Chemical Engineering Conference Room)
Professor Olivier Dauchot
CEA Saclay, SPEC
"Edwards' Compactivity and Volume Statistics Inside a Granular Pile : An Experimental Point of View"
Granular media have become a fertile ground for testing statistical concepts. Yet, from a theoretical viewpoint, little is known on the typical configurations explored dynamically. Edwards and coworkers argued that mechanically stable configurations compatible with a given volume should be statistically equivalent.
We first reformulate Edwards’ proposal in a more general form, taking into account a possible nonuniformity of the measure and, qualitatively, the presence of a correlation length. This reformulation shows that the equiprobability assumption is both unnecessary and non-testable experimentally.
We then investigate experimentally the size dependence of the free volume distribution over clusters of an increasing number of grains, in a bidimensional granular packing. Our main result is that the logarithm of the probability to find a given free volume per grain in a cluster of N grains scales in a nonextensive way for cluster sizes up to a few hundreds grains. Having factorized this size contribution, we can still extract the intensive part of the configurational entropy, and characterize the distributions with two intensive parameters, the meaning of which is discussed in relation with Edwards’ “compactivity”.
BRIEF ACADEMIC/EMPLOYMENT BACKGROUND:
I am generally interested in non-linear phenomena, out of equilibrium physics and disordered media. I have long been interested in The subcritical transition to turbulence in shear flows and my most recent research interests are the jamming transition and Glassy behaviours in granular media; statistical physics of granular media and fluctuations in out of equilibrium systems