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Particle migration in the rotating flow between co-axial disks



We experimentally examine a dilute suspension of non-neutrally buoyant spherical particles migrating in a simple mixing tank at small but finite Reynolds numbers. We observe that the particles spontaneously migrate to repeatable non-trivial asymptotic locations within toroidal structures, located above and below at-disk impellers. The asymptotic migration positions include both the exact center of the torus and intermediate higher-order cluster locations within the flow whose stability is dependent on flow and particle conditions. Furthermore, we note that the particle clusters seem to coincide with the location of unmixed islands within the underlying fluid flow. We also observe a migratory competition when multiple particles are introduced into the flow. © 2006 American Institute of Chemical Engineers AIChE J, 2006