Modeling depth-averaged velocity and boundary shear in trapezoidal channels with secondary flows

Donald W. Knight*, Mazen Omran, Xiaonan Tang

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

93 Citations (Scopus)


The Shiono and Knight method (SKM) offers a new approach to calculating the lateral distributions of depth-averaged velocity and boundary shear stress for flows in straight prismatic channels. It accounts for bed shear, lateral shear, and secondary flow effects via 3 coefficients - f, λ, and Γ - thus incorporating some key 3D flow feature into a lateral distribution model for streamwise motion. The SKM incorporates the effects of secondary flows by specifying an appropriate value for the Γ parameter depending on the sense of direction of the secondary flows, commensurate with the derivative of the term Hρ(UV)d. The values of the transverse velocities, V, have been shown to be consistent with observation. A wide range of boundary shear stress data for trapezoidal channels from different sources has been used to validate the model. The accuracy of the predictions is good, despite the simplicity of the model, although some calibration problems remain. The SKM thus offers an alternative methodology to the more traditional computational fluid dynamics (CFD) approach, giving velocities and boundary shear stress for practical problems, but at much less computational effort than CFD.

Original languageEnglish
Pages (from-to)39-47
Number of pages9
JournalJournal of Hydraulic Engineering
Issue number1
Publication statusPublished - Jan 2007
Externally publishedYes


  • Channel flow
  • Mathematical models
  • River flow
  • Secondary flow
  • Turbulent flow
  • Velocity distribution

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