Longitudinal Dispersion in Open Channels

by Attila A. Sooky,

Serial Information: Journal of the Hydraulics Division, 1969, Vol. 95, Issue 4, Pg. 1327-1346

Document Type: Journal Paper


The effects of cross-sectional geometry and velocity distribution on the dispersion process in straight, uniform open channels with large width-to-depth ratio are investigated. The method of investigation follows Taylor's approach and thus the results apply after the elapse of an initial period during which a constant dispersion coefficient has developed. The results of the analysis show that under the assumed conditions the longitudinal dispersion coefficient can be described by the general expresion K = CRu*; in which R = the hydraulic radius, u* = the shear velocity, and C = a factor. The variation of C with basic geometric and dynamic parameters is presented in the form of equations and diagrams for two velocity profiles (logarithmic and power law), and two cross-sectional shaped (triangular and circular arc). It is found that C varies significantly with cross-sectional shape, width-to-hydraulic radius ratio, and the Reynolds number. The calculated values of C and its pattern of variation are compared to available data for open channels with irregular cross section.

Subject Headings: Cross sections | Open channels | Geometrics | Velocity distribution | Hydraulics | Shear stress | Parameters (statistics) | Velocity profile

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