  A multi-scale model is presented for predicting the magnitude and rate of
powder blending in a rotating drum blender. The model combines particle
diffusion coefficient correlations from the literature with advective flow
field information from blender finite element method simulations. The
multi-scale model predictions for overall mixing and local concentration
variance closely match results from discrete element method (DEM) simulations
for a rotating drum, but take only hours to compute as opposed to taking days
of computation time for the DEM simulations. Parametric studies were performed
using the multi-scale model to investigate the influence of various parameters
on mixing behavior. The multi-scale model is expected to be more amenable to
predicting mixing in complex geometries and scale more efficiently to
industrial-scale blenders than DEM simulations or analytical solutions.
