Controlling of segregation in rotating drums by independent end wall rotations

Abstract

We present in this study that particle segregation in rotating drums can be controlled by end wall rotations. While the end wall rotational speed dominates the time required for reaching the steady state, the rotational direction of the end walls determines the segregation patterns and the shearing zone size. New segregation patterns with two well-mixed regions close to the end walls are observed in the drums with the end wall rotates in the direction opposite to the cylindrical wall. The end wall rotation causes the formation of the local valley and hill next to the wall. Particles flow into the valley and down the hill causing the formation of the convective flow cell at bed surface. It is the difference of the axial velocities between the large particles and small particles close to the end walls separating the particles of difference sizes in the axial direction. The controlling of the end wall roughness and rotating directions effectively enlarge the size of the end wall shearing zone; resulting segregation patterns which are different from the previous simple segregation band patterns.