Approach to jamming in an air-fluidized granular bed.

Quasi-two-dimensional bidisperse amorphous systems of steel beads are fluidized by a uniform upflow of air, so that the beads roll on a horizontal plane. The short-time ballistic motion of the beads is stochastic, with non-Gaussian speed distributions and with different average kinetic energies for the two species. The approach to jamming is studied as a function of increasing bead area fraction and also as a function of decreasing air speed. The structure of the system is measured in terms of both the Voronoi tessellation and the pair distribution function. The dynamics of the system is measured in terms of both displacement statistics and the density of vibrational states. These quantities all exhibit tell-tale features as the dynamics become more constrained closer to jamming. In particular the pair distribution function and the Voronoi cell shape distribution function both develop split peaks. And the mean-squared displacement develops a plateau of subdiffusive motion separating ballistic and diffusive regimes. Though the system is driven and athermal, this behavior is remarkably reminiscent of that in dense colloidal suspensions and supercooled liquids. One possible difference is that kurtosis of the displacement distribution peaks at the beginning of the subdiffusive regime.

[1]  Douglas J. Durian,et al.  Diffusing-Wave Spectroscopy of Dynamics in a Three-Dimensional Granular Flow , 1997, Science.

[2]  Ivo Nezbeda,et al.  Detection and characterization of structural changes in the hard-disk fluid under freezing and melting conditions. , 2005, Physical review letters.

[3]  Thirumalai,et al.  Activated dynamics, loss of ergodicity, and transport in supercooled liquids. , 1993, Physical review. E, Statistical physics, plasmas, fluids, and related interdisciplinary topics.

[4]  Martin T. Dove,et al.  Introduction to Lattice Dynamics: Contents , 1993 .

[5]  Statistical characterization of the forces on spheres in an upflow of air. , 2004, Physical review. E, Statistical, nonlinear, and soft matter physics.

[6]  F. Abraham,et al.  Empirical Criterion for the Glass Transition Region Based on Monte Carlo Simulations , 1978 .

[7]  S. Torquato.  Random Heterogeneous Materials , 2002 .

[8]  M. Cates,et al.  Jamming, Force Chains, and Fragile Matter , 1998, cond-mat/9803197.

[9]  Kinetics: Gaussian statistics in granular gases , 2003, Nature.

[10]  Sidney R. Nagel,et al.  Geometric origin of excess low-frequency vibrational modes in weakly connected amorphous solids , 2004, cond-mat/0409687.

[11]  P. Steinhardt,et al.  Bond-orientational order in liquids and glasses , 1983 .

[12]  J. Duran,et al.  Sands, Powders, and Grains , 2000 .

[13]  A. Matzger,et al.  Statistical mechanics of a gas-fluidized particle , 2004, Nature.

[14]  W. Kegel,et al.  Direct observation of dynamical heterogeneities in colloidal hard-sphere suspensions , 2000, Science.

[15]  Aneesur Rahman,et al.  Correlations in the Motion of Atoms in Liquid Argon , 1964 .

[16]  Andrea J Liu,et al.  Vibrations and diverging length scales near the unjamming transition. , 2005, Physical review letters.

[17]  Andrea J. Liu,et al.  Jamming at zero temperature and zero applied stress: the epitome of disorder. , 2003, Physical review. E, Statistical, nonlinear, and soft matter physics.

[18]  Andrea J Liu,et al.  Random packings of frictionless particles. , 2001, Physical review letters.

[19]  G. Cargill.  Dense Random Packing of Hard Spheres as a Structural Model for Noncrystalline Metallic Solids , 1970 .

[20]  J S Olafsen,et al.  Two-dimensional melting far from equilibrium in a granular monolayer. , 2005, Physical review letters.

[21]  Schofield,et al.  Three-dimensional direct imaging of structural relaxation near the colloidal glass transition , 2000, Science.

[22]  Andrea J. Liu,et al.  Nonlinear dynamics: Jamming is not just cool any more , 1998, Nature.

[23]  R. Behringer.  Sands, Powders, and Grains: An Introduction to the Physics of Granular Materials , 1999 .

[24]  Structural signatures of the unjamming transition at zero temperature. , 2006, Physical review. E, Statistical, nonlinear, and soft matter physics.

[25]  P. Harrowell,et al.  Non‐Gaussian behavior and the dynamical complexity of particle motion in a dense two‐dimensional liquid , 1996 .

[26]  H. Jaeger,et al.  Granular solids, liquids, and gases , 1996 .

[27]  S. Rice,et al.  Experimental observations of non-Gaussian behavior and stringlike cooperative dynamics in concentrated quasi-two-dimensional colloidal liquids. , 1999, Physical review. E, Statistical physics, plasmas, fluids, and related interdisciplinary topics.

[28]  S. Torquato,et al.  Random Heterogeneous Materials: Microstructure and Macroscopic Properties , 2005 .

[29]  W. V. Megen,et al.  Tracer diffusion in concentrated colloidal dispersions. II. Non‐Gaussian effects , 1988 .

[30]  M D Shattuck,et al.  Crystallization of a quasi-two-dimensional granular fluid. , 2006, Physical review letters.

[31]  Steven J. Plimpton,et al.  DYNAMICAL HETEROGENEITIES IN A SUPERCOOLED LENNARD-JONES LIQUID , 1997 .

[32]  R. Nedderman.  Statics and Kinematics of Granular Materials: Euler's equation and rates of strain , 1992 .

[33]  E. Bartsch,et al.  Self-Diffusion in Concentrated Colloid Suspensions Studied by Digital Video Microscopy of Core−Shell Tracer Particles , 1998 .

[34]  Matthieu Wyart,et al.  Effects of compression on the vibrational modes of marginally jammed solids. , 2005, Physical review. E, Statistical, nonlinear, and soft matter physics.