Plug flow and the breakdown of Bagnold scaling in cohesive granular flows

Plug flow and the breakdown of Bagnold scaling in cohesive granular flows

Robert Brewster,1 Gary S. Grest,2 James W. Landry,3 and Alex J. Levine1
1Department of Chemistry and Biochemistry, UCLA, Los Angeles, California 90095-1596, USA
2Sandia National Laboratories, Albuquerque New Mexico 87185, USA
3BAE Systems Burlington, Massachusetts 01803, USA
Received 5 September 2005; published 21 December 2005

Cohesive granular media flowing down an inclined plane are studied by discrete element simulations. Previous work on cohesionless granular media demonstrated that within the steady flow regime where gravitational energy is balanced by dissipation arising from intergrain forces, the velocity profile in the flow direction scales with depth in a manner consistent with the predictions of Bagnold. Here we demonstrate that this Bagnold scaling does not hold for the analogous steady flows in cohesive granular media. We develop a generalization of the Bagnold constitutive relation to account for our observation and speculate as to the underlying physical mechanisms responsible for the different constitutive laws for cohesive and noncohesive granular media.

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