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Abstract: The structural features of fiber suspensions are dependent on the fiber alignment in the flows. In this work the orientation distribution function and orientation tensors for semi-concentrated fiber suspensions in converging channel flow were calculated, and the evolutions of the fiber alignment and the bulk effective viscosity were analyzed. The results showed that the bulk stress and the effective viscosity were functions of the rate-of-strain tensor and the fiber orientation state; and that the fiber suspensions evolved to steady alignment and tended to concentrate to some preferred directions close to but not same as the directions of local streamlines. The bulk effective viscosity depended on the product of Reynolds number and time. The decrease of effective viscosity near the boundary benefited the increase of the rate of flow. Finally when the fiber alignment went into steady state, the structural features of fiber suspensions were not dependent on the Reynolds number but on the converging channel angle.

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