 |
|
Granular media
in low-gravity environment
ESA Vip-Gran Instrument for
studying granular media in International Space Station
operational from 2025
In parabolic flights and in sounding rockets (1999-2020) - see also below
In parabolic flights and in sounding rockets (1999-2020) - see also below
Electrical
Transport in Granular Media
Discovered
in
1890, coheration or ``Branly effect'' is an
electrical conduction transition (from an isolating to a
conductive state) in metallic granular media. Our experiment
allows to understand the phenomena linked to this transition
by focusing on the nature of the contacts instead of the
structure of the granular network as usual:
More details
More details
Current
through
a metallic granular powder is noisy, and the noise has
interesting self-similar properties, including intermittency
and scale invariance, with similarities and
differences with fluid turbulence:
More details
More details
Granular Gases
The macroscopic properties of
granular media are strongly related to the physics of the
collisions between grains, and to the absence of thermal
agitation.
In a
general way, the collisions are characterized by a
dissipation of energy (inelastic collision). It is
thus necessary to supply continuously some energy to
this system (e.g. by vibration) in order to keep it
in a stationnary state.
This inelasticity of
collisions leads to particularly interesting dynamic
regimes: when the number of particles increases, a
transition appears between a spatially homogeneous
fluidized state (gas) and a phenomenon of
aggregation of particles (cluster). In the kinetic regime, due to the inelasticity of the collisions, the pressure and the temperature of such a granular gas are governed by a state equation which differs qualitatively from that of a usual gas.
A model of coefficient of restitution dependent on the speed of impact between grains allows to find numerically these experimental results both qualitatively and quantitatively.
The study of the collision statistics of a dissipative granular gas, performed in microgravity (parabolic flights - sounding rocket), show even there surprising results.
