Mixing of granular material in a drum mixer undergoing rotational and rocking motions - II. Segregating particles

This study examines mixtures of particles of unequal sizes in a cylindrical drum both for pure rotation and rotation with vertical rocking. These motions generate mixtures with complex patterns. Such structures are frozen in situ, sliced, and characterized quantitatively using image analysis. For short times, segregation patterns observed in these experiments differ from those anticipated from previous studies in the literature; the large particles tend to concentrate in segregated cores. For long times, the larger particles migrate to the ends of the cylinder, approaching the more commonly observed banding segregation patterns. Under some conditions, near-homogeneous structures are generated, but such systems are meta-stable; additional mixing time results in a mon strongly segregated system. (C) 1998 Elsevier Science S.A. All rights reserved.