Journal
JOURNAL OF CHEMICAL PHYSICS
Volume 136, Issue 1, Pages -Publisher
AMER INST PHYSICS
DOI: 10.1063/1.3673876
Keywords
Brownian motion; diffusion; elasticity; fluctuations; fluidisation; granular materials; hydrodynamics; plates (structures)
Funding
- Granular-Chaos project
- Italian MIUR under FIRB-IDEAS [RBID08Z9JE]
- Italian MIUR under FIRB [RBFR081IUK]
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Velocity and density structure factors are measured over a hydrodynamic range of scales in a horizontal quasi-2D fluidized granular experiment, with packing fractions phi is an element of [10%, 40%]. The fluidization is realized by vertically vibrating a rough plate, on top of which particles perform a Brownian-like horizontal motion in addition to inelastic collisions. On one hand, the density structure factor is equal to that of elastic hard spheres, except in the limit of large length-scales, as it occurs in the presence of an effective interaction. On the other hand, the velocity field shows a more complex structure which is a genuine expression of a non-equilibrium steady state and which can be compared to a recent fluctuating hydrodynamic theory with non-equilibrium noise. The temporal decay of velocity modes autocorrelations is compatible with linear hydrodynamic equations with rates dictated by viscous momentum diffusion, corrected by a typical interaction time with the thermostat. Equal-time velocity structure factors display a peculiar shape with a plateau at large length-scales and another one at small scales, marking two different temperatures: the bath temperature T-b, depending on shaking parameters, and the granular temperature T-g < T-b, which is affected by collisions. The two ranges of scales are separated by a correlation length which grows with f, after proper rescaling with the mean free path. (C) 2012 American Institute of Physics. [doi: 10.1063/1.3673876]
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