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DY: Fachverband Dynamik und Statistische Physik

DY 41: Poster - Pattern/ Nonlinear Dyn./ Fluids/ Granular/ Critical Phen.

DY 41.34: Poster

Donnerstag, 3. April 2014, 17:00–19:00, P3

Statistics of 2D granular assemblies comprised of polygonal particles — •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[1]. Assemblies prepared by the same process, result to packages of the same volume fraction, except fluctuations. In the context of Edwards theory the dependency of the fluctuation strengths on the volume fraction is linked to the compactivity by a granular version of fluctuation dissipation theorem. Provided that the fluctuation strength is a function of the mean volume only one can compute the compactivity by measuring the fluctuations. We performed computer simulations using two dimensional polygonal particles excited periodically by short acceleration pulses and found that the volume fraction is a non-monotonic function of the pulse strength. This allows us to test whether or not the fluctuations are a function of the volume fraction only or not. In the second case an extended version of Edwards theory, containing the angoricity tensor as second state variable, has to be considered[2]. We will calculate the compactivity and if necessary the angoricity. We will compare the results with assemblies prepared by a different process on an otherwise identical systems. Due to Edwards theory, the results should only depend on the granular state variables, but not on details of the protocol. [1] Physica A 157, 1080 (1989) [2] PRL 109,238001 (2012)