Abstract
In this paper, an improved Shiono–Knight model (SKM) has been proposed to calculate the rectangular compound open channel flows by considering a multi-zonal (MZ) approach in modelling turbulence and secondary flows across lateral flow direction. This is an effort to represent natural flows with compound shape more closely. The proposed model improves the estimation of secondary flow by original SKM model to increase the accuracy of depth-averaged velocity profile solution formed within the transitional region between different sections (i.e. between main-channel and floodplain) of compound channel. This proposed MZ model works by sectioning intermediate zones between floodplain and main-channel for running computation in order to improve the modelling accuracy. The modelling results have been validated using the experimental data by national UK Flood Channel Facility. It has been proven to work reasonably well to model secondary flows within the investigated compound channel flow cases and hence produce better representation to their flow lateral velocity profile.
Highlights
In recent years, studies into compound channels have been undertaken due to its importance in representing the seasonal-impact rivers and floodplains
The Shiono–Knight model (SKM) was improved when Shonio and Knight [12] included the effects of secondary flows within the SKM model, which they found that the turbulence and secondary flow occurrences are complicated in compound channel flows due to the lateral exchange of flow momentum between the main-channel and floodplains
Due to its 2D Navier–Stokes assumption, SKM has found to represent the narrow channel flow with less accuracy compared to wide channel flows
Summary
Studies into compound channels have been undertaken due to its importance in representing the seasonal-impact rivers and floodplains. Studies by Yang et al [17] showed that large-scale eddies are formed by instability in regions with high velocity variation, such as at the interface between main-channel and its floodplains of a compound channel flow All these studies showed that the accurate calculation of secondary currents and turbulence are crucial for estimating the flow velocity. Ervine et al [2] based their model by assuming the temporal-mean transverse velocity component in the flow momentum equation to be fraction of the streamwise depthaveraged velocity U d, replacing by KU2d, where K is a weighted coefficient In their model, K was used to account for complex 3D interfacing of the main-channel and floodplain, which includes the effect of horizontal shear layer, mass exchange in and out of each section and any expansion and contraction losses from non-prismatic channels. The proposed model has been validated against the UK Flood Channel Facility (FCF) experimental data
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