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Granular Mixing and Segregation In Zig-Zag Chute Flow

Suman K. Hajra, Deliang Shi, Watson L. Vargas, and J. J. McCarthy. Department of Chemical and Petroleum Engineering, University of Pittsburgh, 1249 Benedum Hall, Pittsburgh, PA 15261

By introducing periodic flow inversions, we have shown both experimentally and computationally that forcing with a value above a critical frequency can effectively eliminate both density and size segregation. The critical frequency is the key to applying this technique and is directly related to the inverse of the characteristic time of segregation. In this work, we study size segregation and propose a generalized size segregation model to determine the critical forcing frequency in these systems. The influences on mixing of the length of each leg of the zig-zag chute and the size ratio of the particles are examined. Mixing is observed instead of segregation when L<UavgtS, where L, Uavg, and tS denote the length of each leg of the zig-zag chute, the average stream wise flow velocity of the particle, and the characteristic time of segregation, respectively.