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 ...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 vis-cosity were analyzed. The results showed that the bulk stress and the effective viscosity were functions of therate-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 stream-lines. The bulk effective viscosity depended on the product of Reynolds number and time. The decrease of ef-fective 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 numberbut on the converging channel angle.展开更多
The available expressions for the effective vis-cosity can not provide good predictions compared with the experiment data measured in the semi-dilute shear flows of fiber suspension with small aspect ratio. The depart...The available expressions for the effective vis-cosity can not provide good predictions compared with the experiment data measured in the semi-dilute shear flows of fiber suspension with small aspect ratio. The departure of the theoretical prediction from the measured data increases with the decrease of the fiber aspect ratio. Therefore, by experi-ment for the fiber with 20 mm diameter, a new expression for the effective viscosity in the semi-dilute shear flows of fiber suspension with small aspect ratio is proposed, the relation-ship between the shear viscosity of fiber suspensions and the fiber concentration is given. The results show that the effec-tive viscosity is not a linear function of the fiber concentra-tion.展开更多
文摘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 vis-cosity were analyzed. The results showed that the bulk stress and the effective viscosity were functions of therate-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 stream-lines. The bulk effective viscosity depended on the product of Reynolds number and time. The decrease of ef-fective 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 numberbut on the converging channel angle.
文摘The available expressions for the effective vis-cosity can not provide good predictions compared with the experiment data measured in the semi-dilute shear flows of fiber suspension with small aspect ratio. The departure of the theoretical prediction from the measured data increases with the decrease of the fiber aspect ratio. Therefore, by experi-ment for the fiber with 20 mm diameter, a new expression for the effective viscosity in the semi-dilute shear flows of fiber suspension with small aspect ratio is proposed, the relation-ship between the shear viscosity of fiber suspensions and the fiber concentration is given. The results show that the effec-tive viscosity is not a linear function of the fiber concentra-tion.
