Flip-over and oscillation phenomena of fiber orientation ellipsoids in Bi-disperse suspension flows

Abstract

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 r a = 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.