The granular Leidenfrost effect: Experiment and theory of floating particle clusters

Granular material is vertically vibrated in a 2-D container: Above a critical shaking strength, and for a sufficient number of beads, a crystalline cluster is elevated and supported by a dilute gaseous layer of fast beads underneath. We call this phenomenon the \emph{granular Leidenfrost effect}. The experimental observations are explained by a hydrodynamic model featuring three dimensionless control parameters: The energy input $S$, the number of particle layers $F$, and the inelasticity of the particle collisions $\varepsilon$. The $(S,F)$ phase diagram, in which the Leidenfrost state lies between the purely solid and gas phases, shows accurate agreement between experiment and theory.