Inelastic gas: an experimental study of vribrofluidized dilute granular media

Klebert Feitosa

Department of Physics, University of Massachusetts


Intense excitation of a small collection of grains produces a fluidized steady state which resembles the state of a molecular gas. However, the macroscopic size of the grains and their dissipative interactions lead to striking differences between the two systems. I will present a study of a granular system composed of spherical beads confined to move on a vertical plane when excited by intense vertical vibrations. The spectrum of velocity fluctuations shows a well defined non-gaussian distribution of velocities. Surprisingly, the distribution is independent of several experimental parameters including the inelasticity of the particles. For a binary granular gas energy equipartition is violated. The temperature ratio between the species, however, is constant in the bulk of the system, dependent on the mass ratio, and insensitive to other experimental parameters. Finally, we study the statistics of power flux into the system. The investigation reveals close agreement with the predictions of the Fluctuation Theorem of Gallavotti-Cohen.

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