Radial segregation of binary-sized ellipsoids in a rotating drum

Rotating drums are widely used in industry for powder mixing, milling, coating and drying processes. Segregation is inevitable when using a rotating drum to mix granules differing in size, density or shape. Size segregation in rotating drums has received comprehensive studies over the past decades, but most of the studies concentrate on spherical particles. Particle shape, as one of the important particle properties, could affect size-induced segregation significantly. However, such an effect is still poorly understood. In this work, DEM is employed to study the radial segregation of binary-sized ellipsoidal particles in a rotating drum. The segregation patterns for both spheres and ellipsoids are presented and compared. The effects of aspect ratio, size ratio and rotating speed on the extent of segregation are investigated. Generally, large particles tend to segregate to the periphery of the bed, whereas small ones are accumulated in the core section. As particle aspect ratio deviates from unity, i.e. elongated or platy shape-type, the extent of segregation is reduced. Small ellipsoidal particles tend to be entrained by large ellipsoids causing less segregation. The decrease of size ratio of small to large particles does not necessarily lead to a higher segregation extent. The results also show that in rolling or cascading regimes, increasing the rotating speed can reduce the extent of segregation for both spheres and ellipsoids. The studies also indicate that the initial states of mixtures do not affect the final segregation patterns.