Madec Christopher, Collin Brivaël, John Soundar Jerome J, Joubaud Sylvain
Univ Lyon, ENS de Lyon, Univ Claude Bernard, CNRS, Laboratoire de Physique, 69367 Lyon Cedex 07, France.
Univ Lyon, Université Claude Bernard Lyon 1, Laboratoire de Mécanique des Fluides et d'Acoustique, CNRS, UMR 5509, Boulevard 11 Novembre, 69622 Villeurbanne CEDEX, Lyon, France.
Phys Rev Lett. 2020 Aug 14;125(7):078004. doi: 10.1103/PhysRevLett.125.078004.
We present an anomalous experimental observation on the rising speed of air bubbles in a Hele-Shaw cell containing a suspension of spherical, neutrally buoyant, non-Brownian particles. Strikingly, bubbles rise faster in suspensions as compared to particle-less liquids of the same effective viscosity. By carefully measuring this bubble speed increase at various particle volume fraction and via velocity field imaging, we demonstrate that this strange bubble dynamics is linked to a reduction in the bulk dissipation rate. A good match between our experimental data and computations based on a Suspension Balance Model (SBM) illustrates that the underlying mechanism for this dissipation-rate deficit is related to a nonuniform particle distribution in the direction perpendicular to the channel walls due to shear-induced particle migration.
