Monodisperse and polydisperse suspension flows form an extensive section of natural and technological flows. These flow structures can be categorized to sedimenting or neutrally buoyant suspensions considering the density ratio between particle phase to dispersion phase. Biological systems, food processing, ceramic injection, dynamic filtration and air conditioning are examples of areas that such flows arise. Various complicated interparticle interactions and their inevitable influence on and from the continuous phase result in some interesting phenomena which are challenging to justify. This research studies axial instabilities of suspension flow in a partially filled Taylor-Couette setup. Previous observations show that when a monodisperse suspension undergoes a rotational shear motion in a partially filled horizontal Couette cell, particles leave their initial uniform distribution and migrate to regions with lower shear rate. This migration helps formation of ring-shape axial concentrated bands. This study examines the noncolloidal neutrally buoyant suspensions of hard spherical particles with average diameters of 150, 360, 850 micron. Using UCON oil (poly ethylene glycol-ran-glycol) as suspending fluid, monodisperse and polydisperse suspensions in partially filled Stokesian Couette-Taylor flow were studied. The results show strong dependence of band number and profile on suspension concentration and filling level. Moreover interesting phenomena in polydisperse suspensions such as different band shape and weak dependence of band formation time on size of constituents were observed.

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