Journal of Fluid Mechanics



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


V. V. R.  Natarajan a1, M. L.  Hunt a1 and E. D.  Taylor a1
a1 Division of Engineering and Applied Sciences, California Institute of Technology, Pasadena, CA 91125, USA

Article author query
natarajan vv   [Google Scholar] 
hunt ml   [Google Scholar] 
taylor ed   [Google Scholar] 
 

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.

(Published Online April 26 2006)
(Received August 24 1994)
(Revised April 24 1995)



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