Fiber suspension flow in a tapered channel: The effect of flow/fiber coupling

被引:28
作者
Krochak, Paul J. [1 ]
Olson, James A. [1 ]
Martinez, D. Mark [2 ]
机构
[1] Univ British Columbia, Dept Mech Engn, Ctr Pulp & Paper, Vancouver, BC V6T 1Z4, Canada
[2] Univ British Columbia, Dept Chem & Biol Engn, Vancouver, BC V6T 1Z3, Canada
基金
加拿大自然科学与工程研究理事会;
关键词
Fiber suspension; Two-way coupling; Fiber orientation; Planar contraction; NUMERICAL-SIMULATION; ORIENTATION DISTRIBUTION; CLOSURE APPROXIMATIONS; PLANAR CONTRACTION; TURBULENT-FLOW; PARTICLES; ANISOTROPY; SLENDER; STRESS; MOTION;
D O I
10.1016/j.ijmultiphaseflow.2009.03.005
中图分类号
O3 [力学];
学科分类号
08 ; 0801 ;
摘要
A numerical model for predicting the flow and orientation state of semi-dilute, rigid fiber suspensions in a tapered channel is presented. The effect of the two-way flow/fiber coupling is investigated for low Reynolds number flow using the constitutive model of Shaqfeh and Fredrickson. An orientation distribution function is used to describe the local orientation state of the suspension and evolves according to a Fokker-Plank type equation. The planar orientation distribution function is determined along streamlines of the flow and is coupled with the fluid momentum equations through a fourth-order orientation tensor. The coupling term accounts for the two-way interaction and momentum exchange between the fluid and fiber phases. The fibers are free to interact through long range hydrodynamic fiber-fiber interactions which are modeled using a rotary diffusion coefficient, an approach outlined by Folgar and Tucker. Numerical predictions are made for two different orientation states at the inlet to the contraction, namely a fully random and a partially aligned fiber orientation state. Results from these numerical predictions show that the streamlines of the flow are altered and that velocity profiles change from Jeffery-Hamel, to something resembling a plug flow when the fiber phase is considered in the fluid momentum equations. This phenomenon was found when the suspension enters the channel in either a pre-aligned, or in a fully random orientation state. When the suspension enters the channel in an aligned orientation state, fiber orientation is shown to be only marginally changed when the two-way coupling is included. However, significant differences between coupled and uncoupled predictions of fiber orientation were found when the suspension enters the channel in a random orientation state. In this case, the suspension was shown to align much more quickly when the mutual coupling was accounted for and profiles of the orientation anisotropy were considerably different both qualitatively and quantitatively. (C) 2009 Elsevier Ltd. All rights reserved.
引用
收藏
页码:676 / 688
页数:13
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