Non-equilibrium length in granular fluids: From experiment to fluctuating hydrodynamics
CNR-ISC and Dipartimento di Fisica, Università Sapienza - p.le A. Moro 2, 00185, Roma, Italy, EU
Accepted: 18 August 2011
Velocity correlations in a quasi-2D driven granular fluid are studied in experiments and numerical simulations. The transverse velocity structure factor reveals two well-defined energy scales, associated with the external “bath temperature” Tb and with the internal granular one, Tg<Tb, relevant at large and small wavelengths, respectively. Experimental and numerical data are discussed within a fluctuating hydrodynamics model, which allows one to define and measure a non-equilibrium coherence length, growing with density, that characterizes order in the velocity field.
PACS: 45.70.-n – Granular systems / 05.20.Dd – Kinetic theory / 05.40.-a – Fluctuation phenomena, random processes, noise, and Brownian motion
© EPLA, 2011