URL: http://iopscience.iop.org/article/10.1209/0295-5075/123/14003
Abstract: Strongly driven granular
media are known to undergo a transition from a gas-like to a
cluster regime when the density of particles is increased.
However, the main mechanism triggering this transition is not
fully understood so far. Here, we investigate experimentally
this transition within a 3D cell filled with beads that are
driven by two face-to-face vibrating pistons in low gravity
during parabolic flight campaigns. By varying large ranges of
parameters, we obtain the full phase diagram of the dynamical
regimes reached by the out-of-equilibrium system: gas, cluster
or bouncing aggregate. The images of the cell recorded by two
perpendicular cameras are processed to obtain the profiles of
particle density along the vibration axis of the cell. A
statistical test is then performed on these distributions to
determinate which regime is reached by the system. The
experimental results are found in very good agreement with
theoretical models for the gas-cluster transition and for the
emergence of the bouncing state. The transition is shown to
occur when the typical propagation time needed to transmit the
kinetic energy from one piston to the other is of the order of
the relaxation time due to dissipative collisions.