Slip-stick excitation and travelling waves excite silo honking
1 University of Cambridge, UK, Department of Applied Mathematics and Theoretical Physics
2 Imperial College London, UK, Department of Mechanical Engineering
3 University of Twente, Netherlands, Department of Mechanical Engineering
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Published online: 30 June 2017
Silo honking is the harmonic sound generated by the discharge of a silo filled with a granular material. In industrial storage silos, the acoustic emission during discharge of PET-particles forms a nuisance for the environment and may ultimately result in structural failure. This work investigates the phenomenon experimentally using a laboratory-scale silo, and successfully correlates the frequency of the emitted sound with the periodicity of the mechanical motion of the grains. The key driver is the slip-stick interaction between the wall and the particles, characterized as a wave moving upwards through the silo. A quantitative correlation is established for the first time between the frequency of the sound, measured with an electret microphone, and the slip-frequency, measured with a high-speed camera. In the lower regions of the tube, both the slip-stick motion and the honking sound disappear.
© The Authors, published by EDP Sciences, 2017
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