Steady state velocity
distributions of an oscillated granular gas
Abstract:
We use a three-dimensional molecular dynamics simulation to
study the single particle distribution function of a dilute
granular gas driven by a vertically oscillating plate at
high accelerations (15g–90g). We find that the
density and the temperature fields are essentially time-invariant above
a height of about 40 particle diameters, where typically 20%
of the grains are contained. These grains form the nonequilibrium
steady-state granular gas with a Knudsen number unity or greater.
In the steady-state region, the probability distribution function of the
horizontal velocity cx (scaled by the local
horizontal temperature) is found to be nearly independent of
height, even though the hydrodynamic fields vary with
height. We find that the high energy tails of the
distribution function are described by a stretched
exponential ~exp(–![[script B]](http://scitation.aip.org/servlet/GetImg?key=PLEEE8000069000001011301000001%3A0%3A0%3A28&t=a&d=a)
c
), where 
depends on the restitution coefficient e
and falls in the range 1.2<<1.6. However, does not vary significantly for a wide
range of friction coefficient values. We find that the
distribution function of a frictionless inelastic hard
sphere model can be made similar to that of a frictional
model by adjusting e. However, there is no single
value of e that mimics the frictional model over a
range of heights.
Phys. Rev. E 69,
011301, (2004).
Manuscript
available in PDF and PS formats.