Axisymmetric granular flow on a bounded conical heap: Kinematics and size segregation

A. B. Isner, J. M. Ottino, P.B. Umbanhower, R. M. Lueptow
Chemical Engineering Science
Conical heap, Discrete element method, Granular materials, Kinematics, segregation

Free surface flows of granular materials in bounded axisymmetric geometries such as a cylindrical silo are poorly understood. In particular, a detailed description of the local three-dimensional velocity field and predictive models for segregation are lacking. Here, the details of the kinematics of flow in a rising conical heap formed by a centrally fed mixture of spherical particles are investigated using Discrete Element Method (DEM) simulations in a wedge-shaped geometry with periodic azimuthal boundaries. The dependence of the streamwise and surface normal velocity components on the inlet flow rate and silo radius for size-bidisperse and monodisperse mixtures of glass spheres is characterized. Compared to a wedge with frictional sidewalls, the flowing layer is much thicker on average in the axisymmetric case. Using the scalings for kinematics obtained from the DEM simulations, a modified continuum advection-diffusion-segregation model accurately predicts steady-state segregation for axisymmetric conical heap flows of size-bidisperse mixtures.

Keywords: Granular materials, Discrete element method, Conical heap, Segregation, Kinematics

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