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Local measurements of velocity fluctuations and diffusion coefficients for a granular material flow

Published online by Cambridge University Press:  26 April 2006

V. V. R. Natarajan ,
M. L. Hunt  and
E. D. Taylor
V. V. R. Natarajan
Affiliation:
Division of Engineering and Applied Sciences, California Institute of Technology, Pasadena, CA 91125, USA
M. L. Hunt
Affiliation:
Division of Engineering and Applied Sciences, California Institute of Technology, Pasadena, CA 91125, USA
E. D. Taylor
Affiliation:
Division of Engineering and Applied Sciences, California Institute of Technology, Pasadena, CA 91125, USA
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Abstract

Measurements were made of two components of the average and fluctuating velocities, and of the local self-diffusion coefficients in a flow of granular material. The experiments were performed in a 1 m-high vertical channel with roughened sidewalls and with polished glass plates at the front and the back to create a two-dimensional flow. The particles used were glass spheres with a nominal diameter of 3 mm. The flows were high density and were characterized by the presence of long-duration frictional contacts between particles. The velocity measurements indicated that the flows consisted of a central uniform regime and a shear regime close to the walls. The fluctuating velocities in the transverse direction increased in magnitude from the centre towards the walls. A similar variation was not observed for the streamwise fluctuations. The self-diffusion coefficients showed a significant dependence on the fluctuating velocities and the shear rate. The velocity fluctuations were highly anistropic with the streamwise components being 2 to 2.5 times the transverse components. The self-diffusion coefficients for the streamwise direction were an order-of-magnitude higher than those for the transverse direction. The surface roughness of the particles led to a decrease in the self-diffusion coefficients.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 304 , 10 December 1995 , pp. 1 - 25
Copyright
© 1995 Cambridge University Press

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