Size segregation in driven granular media

ORAL

Abstract

Granular flows involve grains of different sizes and mass densities, which either remain well-mixed or segregate. We perform discrete element simulations of model granular systems composed of frictionless, bidisperse disks (with diameter Dl and Ds, mass density ρl and ρs, for large and small disks) under gravity and driven by either simple shear or vibration to understand parameters that control mixing and segregation. We have shown that sheared granular system possess 1) a geometrically-segregated regime, where the system becomes increasingly segregated with decreasing Ds/Dl, 2) a weight-segregated regime, where the system becomes less segregated as Ds/Dl decreases further, and 3) well-mixed states. We identified the boundaries between these three regimes as a function of Ds/Dl and ρs/ρl. We performed similar studies of vibrated systems to determine if the boundaries between mixed and segregated states depend on the driving method. We show that the large particles rise to the top only if ρl<ρs, i.e. we only find weight-segregation in vibrated systems. We also show that by driving only large particles in vibrated systems, large particles will rise for intermediate packing fractions (0.7>φ>0.5).

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Presenters

  • Philip Wang

    Mechanical Engineering and Materials Science, Yale University

Authors

  • Philip Wang

    Mechanical Engineering and Materials Science, Yale University

  • Abe Clark

    Naval Postgraduate School, Physics, Naval Postgraduate School

  • Nicholas Ouellette

    Civil and Environmental Engineering, Stanford University, Stanford University

  • Mark Shattuck

    Benjamin Levich Institute and Physics Department, The City College of the City University of New York, Department of Physics and Benjamin Levich Institute, The City College of the City, University of New York, City College of New York, Department of Mechanical Engineering & Materials Science, City College New York, Physics, The City College of the City University of New York, The City College of New York

  • Corey Shane O'Hern

    Yale Univ, Department of Mechanical Engineering & Materials Science, Yale University, Department of Mechanical Engineering and Materials Science, Yale University, Mechanical Engineering and Materials Science, Yale University, Mechanical Engineering & Material Science, Physics, and Applied Physics, Yale University, Yale University