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arXiv · 1411.6033

Grains unchained: local fluidization of a granular packing by focused ultrasound

Pierre Lidon·Nicolas Taberlet·Sebastien Manneville
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Abstract

We report experimental results on the dynamics of a granular packing submitted to high-intensity focused ultrasound. Acoustic radiation pressure is shown to remotely induce local rearrangements within a pile as well as global motion around the focal spot in an initially jammed system. We demonstrate that this fluidization process is intermittent for a range of acoustic pressures and hysteretic when the pressure is cycled. Such a first-order-like unjamming transition is reproduced in numerical simulations in which the acoustic pressure field is modeled by a localized external force. Further analysis of the simulated packings suggests that in the intermittent regime unjamming is not associated with any noticeable prior structural signature. A simple two-state model based on effective temperatures is proposed to account for these findings.

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Pierre Lidon, Nicolas Taberlet, Sebastien Manneville. 2014-11-21. Grains unchained: local fluidization of a granular packing by focused ultrasound. https://doi.org/10.1039/c5sm02060c

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