Direct numerical simulation of low Reynolds number flows in an open-channel with sidewalls

Younghoon Joung, Sung Uk Choi

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Abstract

A direct numerical simulation of low Reynolds number turbulent flows in an open-channel with sidewalls is presented. Mean flow and turbulence structures are described and compared with both simulated and measured data available from the literature. The simulation results show that secondary flows are generated near the walls and free surface. In particular, at the upper corner of the channel, a small vortex called inner secondary flows is simulated. The results show that the inner secondary flows, counter-rotating to outer secondary flows away from the sidewall, increase the shear velocity near the free surface. The secondary flows observed in turbulent open-channel flows are related to the production of Reynolds shear stress. A quadrant analysis shows that sweeps and ejections are dominant in the regions where secondary flows rush in toward the wall and eject from the wall, respectively. A conditional quadrant analysis also reveals that the production of Reynolds shear stress and the secondary flow patterns are determined by the directional tendency of the dominant coherent structures.

Original languageEnglish
Pages (from-to)854-874
Number of pages21
JournalInternational Journal for Numerical Methods in Fluids
Volume62
Issue number8
DOIs
Publication statusPublished - 2010 Mar 1

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All Science Journal Classification (ASJC) codes

  • Computational Mechanics
  • Mechanics of Materials
  • Mechanical Engineering
  • Computer Science Applications
  • Applied Mathematics

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