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Surface velocity in three-dimensional granular tumblers

Published online by Cambridge University Press:  20 July 2006

NICHOLAS A. POHLMAN
Affiliation:
Department of Mechanical Engineering, Northwestern University, Evanston, IL 60208, USA
STEVEN W. MEIER
Affiliation:
Department of Chemical and Biological Engineering, Northwestern University, Evanston, IL 60208, USA
RICHARD M. LUEPTOW
Affiliation:
Department of Mechanical Engineering, Northwestern University, Evanston, IL 60208, USA
JULIO M. OTTINO
Affiliation:
Department of Mechanical Engineering, Northwestern University, Evanston, IL 60208, USA Department of Chemical and Biological Engineering, Northwestern University, Evanston, IL 60208, USA

Abstract

A fundamental characteristic of granular flows is that they are typically restricted to thin layers of rapid surface flow. Thus, a complete understanding of surface flows is key for an accurate representation of the dynamics of the entire flow. Experiments were conducted in three-dimensional tumblers: cylindrical tumblers of various diameters, a double-cone tumbler, and a spherical tumbler, the Froude number for the last two being a function of the local geometry and ranging from $2.6\times10^{-5}$ to $7.5\times10^{-4}$. Surface velocity measurements for 1 mm and 2 mm glass particles were obtained using particle tracking velocimetry. Results indicate that the streamwise surface velocity at the midpoint of the flowing layer is a linear function of local flowing layer length, regardless of tumbler shape, particle size, rotation rate, and fill fraction. In addition, the axial velocity of particles at the free surface is negligible. These results are key for the development of three-dimensional models of granular flows.

Type
Papers
Copyright
© 2006 Cambridge University Press

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