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Title: Piano waves in a vibrated granular material

Description: A granular material (60 microns glass particles) is vibrated vertically under reduced pressure (of the order of 1 Torr): subharmonic standing waves appear for a range of frequency depending on pressure. Grain motion is vertical: the layer expands and compresses in adjacent regions. The waves are due to gas diffusion into the granular material. Dimensionless acceleration, gamma, of the cell is of order 3. For larger gamma, sloshing waves at f/4 appear.

Credits: Video by Jean-Philippe Matas

References: Matas, J.-P., Uehara, J. & Behringer, R.P. (2008) "Gas-driven subharmonic waves in a vibrated twophase granular material", EPJ E, 25, 431-438.

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Contributed By: Jean-Philippe Matas

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