Particle mixing in a nearly filled horizontal cylinder through phase inversion

A procedure for homogeneously mixing two different sizes of particles in a horizontally rotating cylinder is presented. It was found that different cylinder rotation rates produce inverted segregation patterns. A radial core of small particles is formed at low rotation rates and a core of large particles is formed at high rotation rates. A simple force model is presented that can predict the particular segregation pattern for given rotation rates and particle sizes. A homogeneous mixture can be obtained by alternating between rotation rates at which particles occupy corresponding radial positions.