Numerical simulation of particle dynamics in different flow regimes in a rotating drum

Flow regimes in a horizontal rotating drum are important to industrial applications but the underlying mechanisms are not clear. This paper investigated the granular flow dynamics in different regimes using the discrete element method. By varying the rotation speed and particle–wall sliding friction over a wide range, six flow regimes were produced. The macroscopic and microscopic behaviour of the particle flow were systematically analysed. The results showed that the angle of repose of the moving particle bed had a weak dependence on the rotation speed in the slumping and rolling regimes, and increased significantly as the flow transited to the cascading and cataracting regimes. The mean flow velocity increased with the rotation speed, but the normalised velocity against the drum speed in the continuous regimes collapsed into a single curve, which can be well described by a log-normal distribution. The particle bed at low rotation speed had a similar density to those of the random loose packing, and became more dilated with the increase of the rotation speed. Similarly, the mean coordination number showed linear dependence on the drum speed. Both the collision energy and collision frequency increased with the rotation speed. However, the normalised collision energy in different regimes can be fitted with a simple scaling law.

Flow regimes in a horizontally rotating drum were investigated by DEM simulation. By varying the rotation speed and particle–wall sliding friction, six flow regimes were produced. The macroscopic and microscopic properties of particle flow were systematically analysed. The results showed although different flow regimes can be observed macroscopically, simple scaling laws exist as indicated by the normalised statistical distribution in terms of particle velocity, collision energy and frequency at a microscopic, particle scale.Figure optionsDownload as PowerPoint slide