Abstract
The lateral velocity distribution of flow in the shear layer of open channel is required to many problems in river and eco-environment engineering, e.g. distribution of pollutant dispersion, sediment transport and bank erosion, and aquatic habitat. It is not well understood about how the velocity varies laterally in the wall boundary layer. This paper gives an analytical solution of lateral velocity distribution in a rectangular open channel based on the depth-averaged momentum equation proposed by Shiono & Knight. The obtained lateral velocity distributions in the wall shear layer are related to the two hydraulic parameters of lateral eddy viscosity (λ) and depth-averaged secondary flow (Γ) for given roughened channels. Preliminary relationships between the above two parameters and the aspect ratio of channel, B/H, are obtained from two sets of experimental data. The lateral width (δ) of the shear layer was investigated and found to relate to the λ and the bed friction factor (f), as described by Equation (26). This study indicates that the lateral shear layer near the wall can be very wide (δ/H = 14.6) for the extreme case (λ = 0.6 and f = 0.01).
Highlights
In open channel flow, like natural rivers and canals, flows are of highly three-dimensional characteristics owing to the influence of boundaries, varying roughness and non-uniform shapes
Lots of research has been studied on velocity vertical distribution in open channel flows [2] [3] [4] [5], which could not meet the requirement of lateral velocity distribution in engineering application
This paper provides an analytical solution of lateral velocity distribution in the shear layer of rectangular channels, which have various aspect ratios, based on the depth-averaged flow model proposed by Shiono & Knight [7] [8]
Summary
This paper provides an analytical solution of lateral velocity distribution in the shear layer of rectangular channels, which have various aspect ratios, based on the depth-averaged flow model proposed by Shiono & Knight [7] [8]. The obtained analytical solution of lateral velocity distribution is related to three parameters: the eddy viscosity parameter (λ), secondary flow term (Γ) and the bed friction factor (f). Through analysis on the analytical velocity distribution, it was found that the lateral extent of the shear layer is related to the eddy viscosity parameter (λ) and the bed friction factor (f). The left terms of Equation (1) signify the secondary flow per unit weight, which is balanced by the weight component and both the lateral and vertical Reynolds stresses in x direction. Which is the governing equation of depth-averaged flow in the streamwise direction
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