Abstract
The assumption of steady uniform flow permits the computation of the velocity isoline, secondary current and turbulent statistics in open channel flows. However, it becomes important to choose appropriate turbulence models to capture the length scale of turbulence near the interfacial zone of compound channels. This paper not only focusses on capturing the longitudinal vortex and primary mean velocity but also extrapolates the results of numerical analysis to understand the interaction between the main channel and floodplain in asymmetric compound channels. The results of computational fluid dynamics simulation showed that the velocity isoline bulging near the bed of the floodplain and sidewall at the junction, due to high-momentum transport by secondary current, can be captured with Reynolds stress model. Furthermore, by applying the three different cases of channels with varying geometrical aspects, the maximum velocity simulated showed similar results to the experiments where the structure of primary mean velocity is seen to be influenced by momentum transport due to the secondary current.
Highlights
The turbulent structures in compound open channels are characterized by large shear layers generated by the difference of velocity between main channel and floodplain flows
We have discussed the hydrodynamic parameters like secondary current and primary velocity isolines, which showed near exceptional results in capturing major features of flow using the Reynolds shear stress model in CFD
Further analysis of turbulence statistics was given about the interaction of main channel and floodplain flow
Summary
The turbulent structures in compound open channels are characterized by large shear layers generated by the difference of velocity between main channel and floodplain flows. Differential flow velocities in these two different sections create vortices with vertical and longitudinal axis. Due to the in homogeneity of turbulence created in the shear layer region, these induced vortices are latterly defined as plan form vortices and secondary currents, respectively. Many other researchers lately have investigated on this topic and clarified the mean velocity and boundary shear stress in compound channel flows [2]-[7]. The idea of mapping the channel cross section and defining these sub-regions by bounding orthogonal to the isovels is attributed to Leighly [8]
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