Hsiau, S. S. and Hunt, M. L. (1993) Shear-induced particle diffusion and longitudinal velocity fluctuations in a granular-flow mixing layer. Journal of Fluid Mechanics, 251 . pp. 299-313. ISSN 0022-1120. http://resolver.caltech.edu/CaltechAUTHORS:20120309-095444229
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In flows of granular material, collisions between individual particles result in the movement of particles in directions transverse to the bulk motion. If the particles were distinguishable, a macroscopic overview of the transverse motions of the particles would resemble a self-diffusion of molecules as occurs in a gas. The present granular- flow study includes measurements of the self-diffusion process, and of the corresponding profiles of the average velocity and of the streamwise component of the fluctuating velocity. The experimental facility consists of a vertical channel fed by an entrance hopper that is divided by a splitter plate. Using differently-coloured but otherwise identical glass spheres to visualize the diffusion process, the flow resembles a classic mixing-layer experiment. Unlike molecular motions, the local particle movements result from shearing of the flow; hence, the diffusion experiments were performed for different shear rates by changing the sidewall conditions of the test section, and by varying the flow rate and the channel width. In addition, experiments were also conducted using different sizes of glass beads to examine the scaling of the diffusion process. A simple analysis based on the diffusion equation shows that the thickness of the mixing layer increases with the square-root of downstream distance and depends on the magnitude of the velocity fluctuations relative to the mean velocity. The results are also consistent with other studies that suggest that the diffusion coefficient is proportional to the particle diameter and the square-root of the granular temperature.
|Additional Information:||© 1993 Cambridge University Press. Received 14 November 1991 and in revised form 8 November 1992. Published online: 26 April 2006. The authors would like to thank Professors Christopher Brennen and Rolf Sabersky for their helpful discussions and encouragement.|
|Official Citation:||S. S. Hsiau and M. L. Hunt (1993). Shear-induced particle diffusion and longitudinal velocity fluctuations in a granular-flow mixing layer. Journal of Fluid Mechanics, 251 , pp 299-313 doi:10.1017/S0022112093003428|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Ruth Sustaita|
|Deposited On:||09 Mar 2012 18:50|
|Last Modified:||26 Dec 2012 14:56|
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