Influence of Downstream Channel Width on Flow Features in a T-Shaped Open-Channel Confluence
Publication: Journal of Irrigation and Drainage Engineering
Volume 149, Issue 11
Abstract
Open-channel confluences are important junctions in natural and human-made channel networks. Different controls of the confluence hydrodynamics have already been studied intensively, often in schematized geometrical configurations. The T-shaped planform with branches having rectangular cross-sections of equal width is a popular geometry in lab experiments and numerical modeling. However, limited research has been conducted concerning the influence on the flow features of widening or narrowing the downstream branch in such a confluence. Therefore, four geometrical cases with a different downstream channel width were studied with large eddy simulations, while keeping the tributary-dominant discharge ratio, the width of the upstream branches, and the tailwater depth constant. The effect of increasing the downstream-to-upstream branch width ratio was analyzed with regard to the water surface shape, the stagnation zone location, the tributary inflow angles at the interface with the junction, the separation zone dimensions, the flow acceleration toward the vena contracta, the secondary flow patterns and intensity, the turbulent kinetic energy in the shear layers, the bed shear stresses and the backwater effects in the upstream branches. When comparing the numerically predicted upstream-to-downstream water depth ratios with those predicted by the single analytical model applicable to confluences with unequal channel widths, it is found that both models capture the reduction of the upstream-to-downstream water depth ratios when widening the downstream branch, but benchmark cases show that the numerical model predicts the correct relative magnitude of the water depth ratios in the main channel and the tributary channel, contrary to the analytical model.
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Data Availability Statement
All simulation cases, numerical results and flow profiles that support the findings of this study are available from the corresponding author upon reasonable request.
Acknowledgments
This work was performed using the computational facilities of the HPC infrastructure of Ghent University. The first author is supported by a doctoral research grant by the China Scholarship Council (CSC), with co-funding by the Special Research Fund (BOF) of Ghent University.
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Journal of Irrigation and Drainage Engineering
Volume 149 • Issue 11 • November 2023
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© 2023 American Society of Civil Engineers.
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Received: Feb 10, 2023
Accepted: Jul 23, 2023
Published online: Sep 15, 2023
Published in print: Nov 1, 2023
Discussion open until: Feb 15, 2024
ASCE Technical Topics:
- Channel flow
- Channels (waterway)
- Design (by type)
- Engineering fundamentals
- Flow (fluid dynamics)
- Flow patterns
- Fluid dynamics
- Fluid mechanics
- Geometrics
- Highway and road design
- Hydraulic engineering
- Hydraulic structures
- Hydrologic engineering
- Models (by type)
- Numerical models
- Open channels
- River engineering
- Rivers and streams
- Shear stress
- Stress (by type)
- Structural analysis
- Structural engineering
- Water and water resources
- Waterways
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