Numerical solution of fiber suspension flow through a parallel plate channel by coupling flow field with fiber orientation distribution

The coupled flow kinematics and fiber orientation distribution were computed to study the development of fiber suspension flows through a parallel plate channel. The effect of fiber-concentration distribution on the flow field was also examined, The suspension used in the computations consisted of high aspect-ratio rigid fibers in a Newtonian fluid. A parabolic velocity profile for a Newtonian flow and an isotropic fiber orientation were taken at the inlet of the channel. Planar orientations of a large number of fibers were evaluated from computation of the Jeffery equation along the streamlines (statistical scheme, the number of fibers N = 180) instead of direct solutions of the Fokker-Plank equation or the evolution equation of the fourth-order orientation tensor with a closure approximation. For the uniform concentration of fibers, the anisotropic characteristics of fiber orientations and stress field remarkably appear in the region near the inlet. As a result, the flow kinematics for fiber suspensions can change more significantly from the Newtonian counterpart in the region near the inlet as the volume fraction and/or aspect-ratio of fibers increase. When the volume fraction of fibers decreases in the width direction as the channel wall is approached, the velocity profile becomes more plug-like and the anisotropic characteristics more remarkably appear than those fur the uniform concentration case. (C) 2001 Elsevier Science B.V. All rights reserved.