About this Journal Submit a Manuscript Table of Contents
Abstract and Applied Analysis
Volume 2013 (2013), Article ID 845872, 8 pages
http://dx.doi.org/10.1155/2013/845872
Research Article

Direct Numerical Simulation of Concentration and Orientation Distribution of Fibers in a Mixing Layer

1Key Laboratory for Ferrous Metallurgy and Resources Utilization of Ministry of Education, Wuhan University of Science and Technology, Wuhan 430081, China
2College of Aeronautics and Astronautics, Zhejiang University, Hangzhou 310027, China
3College of Mechanical Engineering, Ningbo University of Technology, Ningbo 315211, China

Received 5 September 2013; Accepted 12 October 2013

Academic Editor: Jianzhong Lin

Copyright © 2013 Kun Zhou et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

The concentration and orientation of suspended fibers in a mixing layer are investigated numerically. Two cases (diffusive and nondiffusive) are investigated for the fiber concentration distribution. The fine structures of the instantaneous distributions under these two cases are very different due to molecular diffusion. Sharp front of concentration is observed in the nondiffusive case. However, there is no obvious difference in the mean concentration between the two cases. With regard to the orientation, a fiber may rotate periodically or approach an asymptotic orientation, which is determined by a determinant defined with the stain rate. The symmetric part of the strain rate tends to make a fiber align to an asymptotic orientation, while the antisymmetric part drives a fiber to rotate. When a fluid parcel passes through a region with relatively high shear rate, fibers carried by the fluid parcel are most likely to rotate incessantly. On the other hand, in the region of relatively high extension rate, fibers tend to align to some asymptotic orientation. Generally, fibers tend to align with the shear plane. This fact has significant implications in predicting the rheological properties of fiber suspension flows.