American Society of Civil Engineers

Dispersion in Sediment-Laden Stream Flow

by Chiu-On Ng, M.ASCE, (Asst. Prof., Dept. of Mech. Engrg., Univ. of Hong Kong, Pokfulam Rd., Hong Kong)

Journal of Engineering Mechanics, Vol. 126, No. 8, August 2000, pp. 779-786, (doi:

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Document type: Journal Paper
Abstract: A theory is developed to demonstrate the effects of sorptive exchange on the transport of a chemical in a sediment-laden open-channel flow. Based on the multiple-scale method of homogenization, a depth-averaged transport equation is deduced up to a long timescale. The dispersion coefficient is the sum of a modified Taylor dispersion coefficient and a dispersion coefficient due to a finite rate of mass exchange between dissolved phase in the water column and sorbed phase on suspended particles. These coefficients are functions of the suspension number and the bulk solid-water distribution ratio. It is shown that, for sufficiently large particles and solid fractions, enhancement of the longitudinal dispersion coefficient due to the sorptive exchange can be significant and should be included in a comprehensive model.

ASCE Subject Headings:
Open channel flow
Suspended sediment