Turbulence Measurements of Dye Concentration and Effects of Secondary Flow on Distribution in Open Channel Flows
Publication: Journal of Hydraulic Engineering
Volume 129, Issue 5
Abstract
This paper presents simultaneous turbulence measurements of velocity and tracer concentration using a combination of laser Doppler anemometer (LDA) and laser induced fluorescence (LIF) in rectangular and compound channels. Secondary flow, Reynolds stresses, Reynolds fluxes, and dye concentration distributions were measured near the water surface in both channels. An investigation of the effect of secondary flow on passive contaminant diffusion processes was carried out with relatively weak secondary flow in the rectangular channel and relatively strong secondary flow in the compound channel. The results show that the secondary flow clearly influences the spreading of the tracer concentration and the location of concentration peak, being different from the injection location. The transport rate of solute due to the secondary flow is not significant in the rectangular channel case but significant in the compound channel case. The transverse eddy viscosity is demonstrated to be equal to the transverse eddy diffusivity. The transverse eddy diffusivity near the water surface is larger than the vertical one. The Fickian law is valid in most regions investigated, but there are some regions where the Reynolds flux and concentration gradients are locally of the same sign due to the influence of secondary flow on the concentration distribution.
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Published In
Journal of Hydraulic Engineering
Volume 129 • Issue 5 • May 2003
Pages: 373 - 384
Copyright
Copyright © 2003 American Society of Civil Engineers.
History
Received: Sep 15, 2000
Accepted: Oct 21, 2002
Published online: Apr 15, 2003
Published in print: May 2003
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