Fiber suspension flow and fiber orientation through a parallel plate channel were numerically simulated for mono- and bi-disperse fiber suspensions in order to study the mechanism of the evolution of fiber orientation distribution. In the present simulations, fiber-fiber interaction was not taken into account.
For suspensions including small aspect-ratio fibers, flip-over or oscillation phenomenon of the orientation ellipsoid was predicted. For the
ra = 10 + 40 (bi-dispersion including fibers with aspect-ratio
ra = 10 and
ra = 40) and
ra=10 + 100 suspensions, fibers with
ra = 40 and
ra = 100 almost completely aligned along the channel wall, however these fibers had little influence on the evolution of the orientation ellipsoids for the bi-disperse suspensions because the number of fibers was much lower when the same fiber parameters were assumed for both small and large aspect-ratio fibers. In contrast fibers with
ra = 20 could affect the evolution of the orientation ellipsoids for the bi-dispersion with
ra = 10 + 20. It could be found that the phenomenon taking place, flip-over or oscillation, depends on the initial orientation distribution of fibers, the number of fibers of each aspect-ratio for bi-dispersion and the flow kinematics of fiber suspension.
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