MOLECULAR-DYNAMICS STUDIES OF GRANULAR FLOW-THROUGH AN APERTURE

Molecular dynamics methods are used to Study two-dimensional gravity-d riven granular flow through a horizontal aperture. Two distinct approa ches to modeling the granular particles an studied. (a) Circular parti cles subject to a strongly repulsive short-range interaction, together with normal and tangential frictional damping forces. (b) Rigid nonco nvex particles, each consisting of disks arranged as an equilateral tr iangle, suitably spaced to provide a tangible indentation along each e dge; the same repulsive interactions between disks in different grains and normal frictional damping forces are incorporated, but transverse damping is omitted, with the model relying on grain shape to resist s liding motion. In order to allow accurate measurements under steady-st ate conditions, a continuous-feed approach is adopted, in which grains exiting through the hole are returned to the top of the material in t he container. For both models the output flow is measured as a functio n of aperture size, and the observed behavior is compared with previou s theoretical and experimental results. Tests of the degree to which t he models reproduce the depth independence of the flow are reported, a nd the influence of the container width and the nature of the walls ar e studied. The depth dependence of the pressure, the local stress dist ribution, and the particle flow patterns are also examined.