Experimental Study of a Granular Gas Fluidized by Vibrations

Abstract

Abstract. We report experimental results on the behavior of an ensemble of inelastically colliding particles, excited by a vibrated piston in a vertical cylinder. When the particle number is increased, we observe a transition from a regime where the particles have erratic motions (granular "gas") to a collective behavior where all the particles bounce like a nearly solid body. In the gaslike regime, we measure the pressure at constant volume, and the bed expansion at constant external pressure, as a function of the number N of particles. We also measure the density of particles as a function of the altitude, and find that the "atmosphere" is exponential far enough from the piston. From these three independent measurements, we determine a "state equation" between pressure, volume, particle number and the vibration amplitude and frequency.

Vibrated Granular Media as Experimentally Realizable Granular Gases

“…The time averaged pressure at the upper wall is displayed in Fig. 2 as a function of n for various f : from the experiments of Falcon et al [1] (see Fig. 2a), from our simulations with velocity dependent restitution coefficient r = r(v) proposed in Eq.…”

“…Motivated by recent 3D experiments on stainless steel spheres, 2 mm in diameter, fluidized by a vibrating piston [1], we choose the simulation parameters to match the experimental ones: in the simulations, the vibrated piston at the bottom of the box has amplitude A = 25 mm and frequencies 5 Hz ≤ f ≤ 50 Hz. The piston is nearly sinusoidally vibrated with a waveform made by joining two parabolas together, leading to a maximum piston velocity given by V = 4Af .…”

“…In this paper, we bridge the gap between experiments and numerics by presenting simulations of strongly vibrated granular materials designed to mimic recent experiments [1,2]. We present the first simulations which resemble the experiments for a large range of parameters.…”

“…We report numerical simulations of strongly vibrated granular materials designed to mimic recent experiments performed both in presence [1] or absence [2] of gravity. We show that a model with impact velocity dependent restitution coefficient is necessary to bring the simulations into agreement with experiments.…”

Ausgewählte Anwendungen von Stoßproblemen

“…Wenn die mittlere freie Weglänge in einem granularen Medium sehr viel kleiner als der charakteristische Durchmesser der Partikel wird, geht das Material in einen gepackten "festen" Zustand über. Den Übergang vom granularen Gas zur granularen Packung dokumentierten beispielsweise Falcon et al [56] experimentell für den Fall von durch Vibrationen angeregten Stahl-Kügelchen.…”