Geometry-controlled Dynamics of Vibrated Granular Media
Résumé
Granular media behave like solids under confinement and as fluids when flowing or shaken. These features have practical implications, for instance in designing granular dampers, where the dissipative properties (friction, inelastic collisions) ultimately depend on the mobility of the particles. Thermal agitation and phase transitions in such media can be induced by vibrations and are typically controlled by the amount of mechanical energy injected into the system. In turn, we experimentally explore how the geometry of the container can help fluidizing the system at constant energy injection. Here, we perform experiments on a two-dimensional vertically vibrated Hele-Shaw cell containing a large number of non-cohesive spherical particles on top of a V-shaped adjustable base. We quantify the dynamics and the energetic state of the system for different container’s shapes and different injected energy, by imaging the velocity field using high speed camera, to track the motion of all particles; the fluidization of the granular medium is unraveled from the estimation of the local compaction and the order parameter, as a function of time. In addition, we perform a statistical analysis of the velocity fluctuations in order to gain insight on the fluidized phase in term of a thermal agitation. In particular, we will focus our presentation on the nonlinear response (period doubling, route to chaos) of such a complex media, which is reminiscent of the nonlinear dynamics of simple ball bouncing on vibrated plate.