Formation of air bubbles during compaction of a granular pack

Cheng Xiang, Rachel Smith, Heinrich M. Jaeger, Sidney R. Nagel

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4 Scopus citations


When loosely packed granular material in a long tube is tapped, the material collapses into a more dense state. For fine-grained material and with interstitial air present, this compaction occurs as waves of apparent avalanches transport the grains to a lower height. We find that these avalanches are due to a train of air bubbles rising within the material. We investigate how the formation of bubbles depends on the tilt angle of the tube, the size of granular particles, and the pressure of the interstitial gas between the particles. We estimate the interaction between the air and the granular medium that is necessary for the bubbles to form. The estimates are in quantitative agreement with our experimental observations.

Original languageEnglish (US)
Article number123305
JournalPhysics of Fluids
Issue number12
StatePublished - 2008

Bibliographical note

Funding Information:
We thank E. Corwin, T. Humphrey, S. Lani, M. Möbius, J. Royer, C. Sowers, L. Xu, and L.-N. Zou for fruitful discussions. This work was supported by the NSF under the MRSEC program.


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