Abstract
When a container filled with granular material is subjected to sinusoidal vibration in microgravity, dependent on the amplitude of the oscillation, the granulate may exhibit one of two distinct dynamical modes: at low amplitude, a gas-like state is observed, where the particles are relatively homogeneously distributed within the container, almost independent of the phase of the oscillation. In contrast, for large amplitude, collective motion of the particles is favoured, termed collect-and-collide regime. Both regimes are characterized by very different dissipation characteristics. A recent model predicts that the regimes are separated by a sharp transition due to a critical amplitude of the vibration. Here we confirm this prediction of a sharp transition and also the numerical value of the critical amplitude by means of experiments performed under conditions of weightlessness.
Highlights
1.1 Granular dampersWhen granular particles collide with one another or with container walls, they dissipate mechanical energy
For amplitude A ≲ 30 mm the system is in the gas state where the energy dissipation rate is low, ( Pdiss ≲ 7 mW ) while for A ≳ 30 mm the system is in the collect-andcollide regime, characterized by larger dissipation rate, Pdiss ≳ 30 mW
When a granular damper is vibrated under conditions of microgravity, the energy dissipation rate depends strongly on the amplitude of the vibration, A, but shows no significant dependence on the frequency
Summary
1.1 Granular dampersWhen granular particles collide with one another or with container walls, they dissipate mechanical energy. When exposed to oscillations of an adequately high vibrational energy ( Ē ∝ ω2A2 , where and A are, respectively, the angular frequency and amplitude of the vibration), the particles will overcome the sedimenting force of gravity, collide with one another and the walls of the housing container and, dissipate energy. This dissipation attenuates the vibration and, damps the vibrating system [8,9,10,11,12,13,14]. That the simplified, gravity-free systems studied here are not without direct real-world application – see, for
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