Equation of state of a granular gas homogeneously driven by particle rotations

Eric Falcon (1) , Jean-Claude Bacri (1) , Claude Laroche (1)

1 MSC - Matière et Systèmes Complexes

We report an experimental study of a dilute ''gas'' of magnetic particles subjected to a vertical alternating magnetic field in a 3D container. Due to the torque exerted by the field on the magnetic moment of each particle, a spatially homogeneous and chaotic forcing is reached where only rotational motions are driven. This forcing differs significantly from boundary-driven systems used in most previous experimental studies on non equilibrium dissipative granular gases. Here, no cluster formation occurs, and the equation of state displays strong analogy with the usual gas one apart from a geometric factor. Collision statistics is also measured and shows an exponential tail for the particle velocity distribution. Most of these observations are well explained by a simple model which uncovers out-of-equilibrium systems undergoing uniform ''heating''.

Mots clés: Granular system; dissipative granular gas; magnetic materials; experiment; homogeneous and random forcing; rotational motions; particle velocity distribution; equation of state; collision statistics

Domaines: Autre [cond-mat.other]; Dynamique Chaotique [nlin.CD]; Mécanique statistique [cond-mat.stat-mech]; Matière Molle [cond-mat.soft]

Eric Falcon, Jean-Claude Bacri, Claude Laroche. Equation of state of a granular gas homogeneously driven by particle rotations. EPL - Europhysics Letters, 2013, 103, pp.64004. ⟨10.1209/0295-5075/103/64004⟩. ⟨hal-00835674v2⟩