Berlin 2015 – scientific programme

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DY: Fachverband Dynamik und Statistische Physik

DY 4: Granular Matter / Contact Dynamics Part I

DY 4.3: Talk

Monday, March 16, 2015, 10:00–10:15, BH-N 128

About the adaptability of Edwards’ theory to 2D granular assemblies — •Volker Becker and Klaus Kassner — Institut für theoretische Physik, Otto-von-Guericke-Universität Magdeburg, Germany

A possible approach for the statistical description of granular assemblies is Edwards’ assumption that all blocked states which occupy the same volume are equally probable (Edwards, Physica A 157,1989). Other authors claimed that a similar approach where all states with the same stress are assumed as equally probable are more suited for developing a granular statistical mechanics, and Blumenfeld et al. (PRL 238001, 2012) argued that only a combined volume-stress ensemble is an appropriate basis for granular statistics.

We performed computer simulations using two dimensional polygonal particles excited periodically by two different protocols, excitation by “pulses of negative gravity“ and excitation by ”rotating gravity“. The first protocol shows a non-monotonous dependency φ(g) of the mean volume fraction on the pulse strengths.

We used the overlapping histogram method in order to test whether or not the volume is described by a Boltzman-like distribution and to calculate the inverse compactivity, up to an additive constant. We found that the mean volume is a unique function of the granular temperature, independently of the protocol and of the branch in φ(g). However, this is not case for the mean stress, which can be different for the same value of compactivity (or the mean volume).