Accurate 3D experimental particle trajectory data, acquired from a laboratory tumbling mill using bi-planar X-ray filming, are used to validate the discrete element method (DEM). Novel numerical characterisation techniques are presented that provide a basis for comparing the experimental and simulated charge behaviour. These techniques are based on fundamental conservation principles, and provide robust, new interpretations of charge behaviour that are free of operator bias. Twoand three-dimensional DEM simulations of the experimental tumbling mill are performed, and the relative merits of eac |