Kinematics of rigid fibers in a turbulent channel flow

Subhani Shaik, René van Hout

Research output: Contribution to journalArticlepeer-review

Abstract

Measurements of concentrations, translational velocities, orientations and rotation rates of seven, straight and rigid fiber types in a fully developed turbulent water channel flow (one-way coupled, Reτ=435) are reported. The aim was to study inertial and length effects on fiber kinematics. Fibers were characterized by Stokes numbers and mean, normalized lengths ranging between 0.02 ¡ St ¡ 0.34 and 16 ≤L¯+≤ 66.8. Except for the longest (L¯+ = 66.8) fibers, a depletion layer was observed near the wall, its width increasing with decreasing St (for a given length). Away from the wall, fibers lagged the fluid, increasingly so with increasing St and L¯+ due to increased drag. In the buffer layer, fiber excess velocities decreased with L¯+ while inertial effects were small. Irrespective of fiber length, all fibers strongly aligned with the streamwise direction in the near-wall region. Fiber rotation rates peak in the buffer layer, and remain nearly constant in the log-layer and wake region. However, peak values decreased with increasing L¯+. Our results suggest intricate coupling between fiber inertia and length in conjunction with the governing turbulence scales.

Original languageEnglish
Article number104262
JournalInternational Journal of Multiphase Flow
Volume158
DOIs
StatePublished - Jan 2023

Keywords

  • Anisotropic particles
  • Digital holography
  • Fibers
  • Orientation and rotation rates
  • Wall-bounded turbulence

All Science Journal Classification (ASJC) codes

  • Mechanical Engineering
  • Fluid Flow and Transfer Processes
  • General Physics and Astronomy

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