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DY: Fachverband Dynamik und Statistische Physik

DY 53: Focus: Disordered Systems/Glasses under Shear (joint session CPP/ DY)

DY 53.2: Talk

Thursday, March 19, 2015, 16:00–16:15, C 243

Thinning and Thickening in Active Microrheology — •Ting Wang and Matthias Sperl — Institut für Materialphysik im Weltraum, DLR, Köln, Germany

When pulling a probe particle in a driven granular system with constant velocity, one can characterize the probe by a velocity-dependent friction coefficient. With increasing control velocity, the friction of the probe keeps constant in the small-velocity regime (linear response), decreases in the moderate-velocity regime (thinning), and then increases in the large-velocity regime (thickening).

There are three distinct processes behind those phenomena: diffusion, damping and direct collision; the magnitude of the pulling velocity determines which process dominates, resulting in thinning or thickening behavior. We confirm this physics picture by stochastic simulation.