Measurements and modeling of open-channel flows with finite semi-rigid vegetation patches

Cheng Zeng, Chi Wai Li

Research output: Journal article publicationJournal articleAcademic researchpeer-review

23 Citations (Scopus)

Abstract

The hydrodynamics of flows through a finite length semi-rigid vegetation patch (VP) were investigated experimentally and numerically. Detailed measurements have been carried out to determine the spatial variation of velocity and turbulence profiles within the VP. The measurement results show that an intrusion region exists in which the peak Reynolds stress remains near the bed. The velocity profile is invariant within the downstream part of the VP while the Reynolds stress profile requires a longer distance to attain the spatially invariant state. Higher vegetation density leads to a shorter adjustment length of the transition region, and a higher turbulence level within the VP. The vegetation density used in the present study permits the passing through of water and causes the peak Reynolds stress and turbulence kinetic energy each the maximum at the downstream end of the patch. A 3D Reynolds-averaged Navier-Stokes model incorporating the Spalart-Allmaras turbulence closure was employed subsequently to replicate the flow development within the VP. The model reproduced transitional flow characteristics well and the results are in good agreement with the experimental data. Additional numerical experiments show that the adjustment length can be scaled by the water depth, mean velocity and maximum shear stress. Empirical equations of the adjustment lengths for mean velocity and Reynolds stress were derived with coefficients quantified from the numerical simulation results.
Original languageEnglish
Pages (from-to)113-134
Number of pages22
JournalEnvironmental Fluid Mechanics
Volume14
Issue number1
DOIs
Publication statusPublished - 1 Feb 2014

Keywords

  • Adjustment length
  • Aquatic vegetation
  • Flow transition
  • Open-channel flow
  • Turbulence model
  • Vegetation patch

ASJC Scopus subject areas

  • Environmental Chemistry
  • Water Science and Technology

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