Fiber orientation in Fiber Suspension Flow through a Parallel Plate Channel and an Abrupt Contraction Channel

Abstract

The orientation of fibers has been investigated experimentally in fiber suspension flows of both Newtonian and viscoelastic fluids through a parallel plate channel and a planar channel with an abrupt contraction, and the development of the fiber orientation has been examined while the fibers flow along the channel. The effects of shear thinning and elasticity on the fiber orientation have been discussed.The fibers lie tangent to the streamlines with an increase in viscoelasticity in the flow through a parallel plate channel and a channel with an abrupt contraction. This phenomenon is essentially equivalent to the phenomenon that a slender body, namely a straight circular cylinder with a large length to diameter ratio, rotates towards a vertical orientation when falling through a quiescent polymer solution. High fiber alignment to the streamlines, thus, is attributed to the shear thinning and elsticity of the suspending fluids; however, elastic effect is most dominant.The state of fiber orientation is strongly influenced by the drastic change of the velocity field due to viscoelasticity and flow rate: the fibers align in a manner of wine-glass shape as the contraction is approached and then the distribution of fibers abruptly expands in the immediate downstream region of the contraction in a highly elastic fluid flow.