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|Title: ||Nuclear magnetic resonance measurements of velocity distributions in an ultrasonically vibrated granular bed|
|Authors: ||Huntley, Jonathan M.|
Sheikh, Nadeem A.
Wildman, Ricky D.
|Keywords: ||Granular materials|
Rapid granular flow
Vibrated granular bed
Nuclear magnetic resonance
Magnetic resonance imaging
|Issue Date: ||2014|
|Publisher: ||© The Authors. Published by The Royal Society|
|Citation: ||HUNTLEY, J.M. ...et al., 2014. Nuclear magnetic resonance measurements of velocity distributions in an ultrasonically vibrated granular bed. Philosophical Transactions of The Royal Society A-Mathematical Physical and Engineering Sciences, 372: 20130185.|
|Abstract: ||We report the results of nuclear magnetic resonance (NMR) imaging experiments on granular beds of mustard grains fluidised by vertical vibration at ultrasonic frequencies. The variation of both granular temperature and packing fraction with height was measured within the three-dimensional cell for a range of vibration frequencies, amplitudes and numbers of grains. Small increases in vibration frequency were found – contrary to the predictions of classical ‘hard-sphere’ expressions for the energy flux through a vibrating boundary – to result in dramatic reductions in granular temperature. Numerical simulations of the grain-wall interactions, using experimentally-determined Hertzian contact stiffness coefficients, showed that energy flux drops significantly as the vibration period approaches the grain-wall contact time. The experiments thus demonstrate the need for new models for ‘soft-sphere’ boundary conditions at ultrasonic frequencies.|
|Description: ||This paper was accepted for publication in the journal Philosophical Transactions of The Royal Society A-Mathematical Physical and Engineering Sciences and the definitive published version is available at http://dx.doi.org/10.1098/rsta.2013.0185|
|Sponsor: ||This paper was supported by funding under Platform Grant EP/F047991/1|
|Version: ||Accepted for publication|
|Publisher Link: ||http://dx.doi.org/10.1098/rsta.2013.0185|
|Appears in Collections:||Published Articles (Mechanical, Electrical and Manufacturing Engineering)|
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