title: Grains unchained: local fluidization of a granular packing by focused ultrasound.
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.
authors.affiliation: Université de Lyon, Laboratoire de Physique, École Normale Supérieure de Lyon, CNRS UMR 5672, 46 allée d'Italie, 69364 Lyon Cedex 07, France. sebastien.manneville@ens-lyon.fr.
authors.forename: Pierre
authors.initials: P
authors.lastname: Lidon
authors.affiliation: Université de Lyon, UFR de Physique, Université Claude Bernard Lyon I, Lyon, France.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Taberlet
authors.affiliation: Université de Lyon, Laboratoire de Physique, École Normale Supérieure de Lyon, CNRS UMR 5672, 46 allée d'Italie, 69364 Lyon Cedex 07, France. sebastien.manneville@ens-lyon.fr.
authors.forename: Sébastien
authors.initials: S
authors.lastname: Manneville
mesh_terms: D008096:Lithotripsy / Q000295:instrumentation*; D008962:Models, Theoretical; D000069453:Ultrasonic Waves; D014465:Ultrasonics / Q000295:instrumentation*