The unique dynamics of a bed of dry granular material in a vertical cylinder rotating at a constant speed

The unique behavior of a bed of monodispersed dry granular matter confined in a rotating vertical cylinder has been investigated using DEM. At a constant rotational speed, the concave free surface shape exhibits an apparent similarity with the hydrodynamic counterpart of the same problem; but there are some unique differences arising from the particulate nature of the medium. In the rotating granular bed, the free surface profile is independent of the density and the size of the particles, but the local gradient of the free surface is not independent of the rotational speed. The results of a simulated experiment exhibit excellent matching with the free surface profiles obtained computationally and thus establish the efficacy of DEM in simulating the rigid body rotation of a particulate medium. However, the simulation results strongly suggest that though globally the bed behavior resembles solid body rotation, locally, the motion of the particles and their distribution is influenced by the discrete nature of the medium.

Graphical abstract