Shear layer turbulence at an unequal depth channel confluence

P. Biron, B. De Serres, A. G. Roy, James Leonard Best

Research output: Chapter in Book/Report/Conference proceedingChapter


A shear layer formed along the interface between two mixing flows is a feature common to all channel confluences whenever there is a velocity differential at some point along the mixing interface. This paper presents results of velocity and turbulence measurements in a shear layer at a natural channel junction. Velocity measurements were obtained using two-component electromagnetic current meters sampling at 20Hz. These records show that the mixing layer between the confluent flows is characterized by turbulence intensities up to five time greater than those in the free stream outside the shear layer. These data not only reveal the highly turbulent nature of the shear layer in both downstream and vertical components but also the spatial and temporal variability of the shear layer position. There scales of motion are present within the signals and are interpreted as representing: i) longer term shifts in the position of the entire shear layer within the junction; ii) the passage of discrete large-scale eddies (Kelvin-Helmholtz instabilities) past the probe; and iii) shorter term, higher magnitude fluctuations associated with coherent motion within these large-scale eddies. The results are presented together with a discussion of the significance of the shear layer for secondary flow, sediment transport and bed morphology at open-channel junctions, and the role that unequal depth confluent channels may have in causing shear layer distortion. (Authors)

Original languageEnglish (US)
Title of host publicationTurbulence: Perspectives On Flow and Sediment Transfer
EditorsN J Clifford, J R French, J Hardisty
PublisherJohn Wiley & Sons, Ltd.
Number of pages17
StatePublished - 1993
Externally publishedYes

ASJC Scopus subject areas

  • General Environmental Science
  • General Earth and Planetary Sciences


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