Axial dispersion of granular material in horizontal rotating cylinders

The discrete element method is used to calculate axial dispersion coefficients for approximately monosized particles in a rotating horizontal cylinder. Axial dispersion within the cylinder is shown to follow Fick's second law, in that the mean squared deviation of axial position of a pulse of particles is proportional to time. The axial dispersion coefficient is found to depend on the particle size, gravity and drum rotation speed, allowing a dimensionless group to be formed using these four quantities. For sufficiently large cylinders, the axial dispersion coefficient is found to be independent of drum diameter. A general argument is given which suggests that axial dispersion in physical beds of approximately monosized particles should follow Fick's second law.

Graphical AbstractDiscrete element method calculations with approximately monosized particles in a horizontal rotating cylinder with wall rougheners give axial dispersion which follows Fick's second law. A general argument is given which suggests that this should be so. For cylinders of sufficiently large diameter, axial dispersion is found to depend on particle size, gravity, and rotation speed.Figure optionsDownload as PowerPoint slide