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Updated: Jun 8, 2026

Fabrication, Operation and Flow Visualization in Surface-acoustic-wave-driven Acoustic-counterflow Microfluidics
Published on: August 27, 2013
Friction-induced amplification of acoustic waves in a low Mach number granular flow
Lénaic Bonneau1, Tristan Catelin-Jullien, B Andreotti
1Physique et Mécanique des Milieux Hétérogènes, UMR 7636, CNRS-ESPCI, 10 rue Vauquelin, 75231 Paris Cedex 05, France.
Abstract:
We show experimentally that, contrary to ordinary fluids, low Mach number granular pipe flows are linearly unstable toward the emission of acoustic waves. Exponential amplification of the waves propagating in the direction opposite to the flow is directly demonstrated. We relate the observed instability to the friction of the grains on the pipe, which pumps energy from the mean flow to coherent elastic waves. We show that the most amplified wavelength is proportional to the ratio of the tube radius to the friction coefficient.
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