Fibre orientation distribution in turbulent fibre suspensions flowing through an axisymmetric contraction

Authors

  • Jianzhong Lin,

    Corresponding author
    1. Institute of Fluid Measurement and Simulation, China Jiliang University, Hangzhou 310018, China
    2. Department of Mechanics, Zhejiang University, Hangzhou 310027, China
    • Institute of Fluid Measurement and Simulation, China Jiliang University, Hangzhou 310018, China.
    Search for more papers by this author
  • Xiaoyu Liang,

    1. Institute of Fluid Measurement and Simulation, China Jiliang University, Hangzhou 310018, China
    2. Department of Mechanics, Zhejiang University, Hangzhou 310027, China
    Search for more papers by this author
  • Shanliang Zhang

    1. Department of Mechanical Engineering, University of Maryland, College Park, MD 20742, U.S.A.
    Search for more papers by this author

Abstract

The Reynolds averaged Navier–Stokes equation was solved numerically with the Reynolds stress model to get the mean fluid velocity and the turbulent kinetic energy in turbulent fibre suspensions flowing through an axisymmetric contraction. The fluctuating fluid velocity was represented as a Fourier series with random coefficients. Then the slender-body theory was used to predict the fibre orientation distribution and orientation tensor. Some numerical results are compared with the experimental ones in the turbulent fibre suspensions flowing through a contraction with a rectangular cross-section. The results show that the fibres with high aspect ratio tend to align its principal axis with the flow direction much easier. High contraction ratio makes the fibre alignment with the flow direction much easier. The contraction ratio has a strong effect on the fibre orientation distribution. Only a small part of the fibre is aligned with the flow direction in the inlet region, while most fibres are aligned with the flow direction when they approach to exit. The fibres are aligned with the flow direction rapidly in the inlet region, after that the fibre orientations change little in the most of the downstream region. The fibres with high aspect ratio are aligned with the flow direction faster when they enter the contraction. The randomising effect of the turbulence becomes significant in the downstream region because of the high turbulent intensity.

Ancillary