Two particle contact lifetime distribution in gravity driven granular flow

ORAL

Abstract

The distribution of two particle contact life times for gravity driven granular flow down an inclined plane are determined from large-scale, three-dimensional discrete element simulations. Results are presented for both cohesive and non-cohesive particles for Hertzian and Hookean contact forces. The distribution of lifetimes is analyzed as a function of height from the surface for different strength $k_n$ of the normal force, coefficient of restitution $e_n$ and coefficient of friction $\mu$. In addition a generalized form of the Bagnold constitutive relation in which the shear stress depends on a sum of terms that are linear and quadratic in the shear rate is proposed for cohesive granular flows. The linear term represents a new mode of momentum transport made possible through the long lived contacts in the network while the quadratic term represents the usual Bagnold contribution from short time scale collisions. For non-cohesive grains, the strength of the linear term disappears as strength of the normal interaction $k_n$ increased.

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Authors

  • Robert Brewster

    UCLA

  • Leonardo Silbert

    University of Chicago

  • Gary S. Grest

    Sandia National Labs, Sandia National Laboratories, Sandia National Laboratories*

  • Alex Levine

    UCLA, University of California, Los Angeles, Department of Chemistry and Biochemistry, University of California, Los Angeles, UCLA Department of Chemistry and Biochemistry, Department of Chemistry, University of California at Los Angeles, Los Angeles, CA 90095, Department of Chemistry and Biochemistry, University of California, Los Angeles, California