title: Diffusion and mobility in a stirred dense granular material.
abstract: We describe a probe of diffusivity (D) and mobility (B) for a dense 2D granular system. We introduce random motion by stirring, and characterize D by particle tracking. To measure B we measure the force needed to push a particle through the medium at fixed velocity, v, using three sizes of tracer particle. We find simple Brownian diffusion, but B depends strongly on v because the force needed to push a tracer through a sample is nearly independent of v. Data for D/B depend on the tracer particle size.
authors.affiliation: Department of Physics and Center for Nonlinear and Complex Systems, Duke University, Durham, NC 27708-0305, USA.
authors.forename: Junfei
authors.initials: J
authors.lastname: Geng
authors.forename: R P
authors.initials: RP
authors.lastname: Behringer
mesh_terms: D055592:Biophysical Phenomena; D001703:Biophysics; D004058:Diffusion; D009038:Motion; D009068:Movement; D010825:Physics / Q000295:instrumentation* / Q000379:methods*; D013314:Stress, Mechanical