American Society of Civil Engineers

Turbulence Measurements of Dye Concentration and Effects of Secondary Flow on Distribution in Open Channel Flows

by Koji Shiono, (Prof. of Envir. Hydrodynamics, Dept. of Civ. & Bldg. Engrg., Loughborough Univ., Leicestershire LE11 3TU, U.K.) and Tong Feng, (Res. Asst., Dept. of Civ. Engrg., Univ. of Manchester Inst. of Sci. Technol., Manchester M60 1QD, U.K.)

Journal of Hydraulic Engineering, Vol. 129, No. 5, May 2003, pp. 373-384, (doi:

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Document type: Journal Paper
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.

ASCE Subject Headings:
Flow distribution
Open channel flow