Paper detail

Growing non-equilibrium length in granular fluids: from experiment to fluctuating hydrodynamics

Velocity correlations in a 2D granular fluid are studied in experiments and numerical simulations. The transverse component of the velocity structure factor reveals two well defined energy scales, associated with the external &#34;bath temperature&#34; $T_b$ and with the internal granular one, $T_g<T_b$, 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 $ξ$, growing with density, that characterizes order in the velocity field.