Granular Flow in partially filled slowly rotating drums  
Many industrial mixing, coating and grinding processes involve rotating a large mass of granular material in a drum. Mixing in a rotating drum The adjacent figure shows a mathematical model for the steady mixing of monodisperse red and blue granular materials. You can also view a jpeg animation of the solution by clicking here (5244 K). As in many granular flows this problem involves a fluid-solid phase transition. Close to the inclined free surface there is a rapid thin granular avalanche, that transports material downslope, and beneath it there is a large solid body region that slowly rotates with the drum providing a net transport upslope. At the interface between the two regions there is strong mass transfer. Initially the granular material is divided into two equal regions of red and blue grains by a straight interface. As the drum rotates, particles at different levels in the avalanche perform circuits around the drum at different speeds and the interface is deformed.


Gray, J.M.N.T. (2001) Granular flow in partially filled slowly rotating drums. J. Fluid. Mech. 441 , 1-29. (pdf)

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Page last modified: December 22, 2000