Orientation state of fibers, which are suspended at very low concentration, in a fully developed Newtonian flow through a parallel plate channel has been computed from the Jeffery's orientation equation. Numerical predictions are also compared with the previous experimental results and the orientation evolution of fibers, whose initial locations and orientation angles at the entrance are assumed to be random, has been studied both along the channel and in the width direction.
Fibers, which are injected in the entry section with orientations tilted to the streamlines, change their orientations to the streamlines during flow. This trend is remarkable in a region with higher velocity gradient, i. e. the region near the wall, in contrast the orientation angles of fibers do change a little in the region near the centerline. Furthermore, it appears that, when the aspect ratio becomes large, the fiber remains oriented most of the time along the streamline and the fiber fips over within a very short time.
It is also clear that the alignment along the streamlines becomes worse from the wall to the centerline in the width direction. This is because that the velocity becomes higher and the velocity gradient becomes lower as the centerline is approached, thus the fibers require a longer distance to reach the alignment along the streamlines.
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