Flow Turbulence over Fixed and Weakly Mobile Gravel Beds

Characteristics of turbulence structure in quasi-2D flows with static and weakly mobile gravel beds are presented. Three sets of measurements with acoustic Doppler velocimeters in an irrigation canal were used: two with subcritical bed shear stress (static beds) and one with the bed shear stress o c...

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Bibliographic Details
Published in:Journal of hydraulic engineering (New York, N.Y.) N.Y.), 2000-09, Vol.126 (9), p.679-690
Main Authors: Nikora, Vladimir, Goring, Derek
Format: Article
Language:English
Subjects:
Applied sciences
Buildings. Public works
Drag
Exact sciences and technology
Flow patterns
Granular materials
Gravel
Hydraulic constructions
Irrigation networks
River flow control. Flood control
Shear flow
Shear stress
Stress analysis
TECHNICAL PAPERS
Turbulence
Turbulent flow
Velocity measurement
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Summary:Characteristics of turbulence structure in quasi-2D flows with static and weakly mobile gravel beds are presented. Three sets of measurements with acoustic Doppler velocimeters in an irrigation canal were used: two with subcritical bed shear stress (static beds) and one with the bed shear stress o close to critical oc (weakly mobile bed). The analyses included vertical distributions of local mean velocities, turbulence intensities, turbulent shear stresses, velocity auto- and cross-spectra, the quadrant method, and high-order velocity moments. A number of properties of turbulence intensities, high-order moments, streamwise bursting parameters, and velocity spectra appeared to be similar for all three flows, but some properties were different. The most important one was an observed reduction in the von Kármán constant for the flow with weakly mobile bed. Comparison of these results with other studies and analogies with drag-reducing flows suggest that at o oc 1 the drag on the bed for a given granular material should be minimized.
ISSN:0733-9429
1943-7900
DOI:10.1061/(ASCE)0733-9429(2000)126:9(679)