Dresden 2014 – scientific programme

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DY: Fachverband Dynamik und Statistische Physik

DY 43: Focus session: Slow Dynamics in Glasses and Granular Matter II (joint session DY/ CPP/ DF)

DY 43.6: Talk

Friday, April 4, 2014, 11:30–11:45, HÜL 186

Granular Microrheology in the Large Force Regime — •Ting Wang¹, Matthias Grob², Annette Zippelius², and Matthias Sperl¹ — ¹Institut für Materialphysik im Weltraum, Deutsches Zentrum für Luft- und Raumfahrt (DLR), 51170 Köln — ²Georg-August-Universität Göttingen, Institut für Theoretische Physik, Friedrich-Hund-Platz 1, 37077 Göttingen

When pulling a particle in a driven granular system with constant force F, the probe particle may approach a steady velocity v. In the large force regime, it was found in our recent simulation that the effective friction coefficient F/v increases with increasing F, being proportional to the square-root of F, while some earlier Brownian dynamics simulations and theories predicted constant friction coefficient. Here, we study the behavior in granular microrheology by a schematic model of mode-coupling theory (MCT) and a simple kinetic theory. Our schematic model qualitatively reproduces the increase of friction tendency but fails to exhibit the square-root law. In the low density limit, the square-root law can be derived from the kinetic theory, based on which, we clarify the discrepancy of the large force behaviors in driven granular systems and Brownian ones.