Numerical Investigation of the Effect of Main Canal Cross-Section Shape on Flow Dynamic at the Rivers’ Junction

Document Type : Research Paper


1 Department of Water Engineering, Faculty of Agriculture, Urmia University, Urmia, Iran.

2 Department of water engineering, Faculty of Agriculture , Urmia University, Urmia, Iran


Studying and recognizing the flow dynamics at the junction and downstream of the junction is essential in designing the stable geometry of prismatic canals and providing a suitable protection solution for river systems. According to field data, the existence of different junction angles and bed discordance between the main and tributary canals is one of the most common physical characteristics of the most natural junction. The present research aims to numerically investigate the effect of main canal cross-section shapes (rectangular and trapezoidal) and junction angles (45° and 90°) on flow dynamics at river junctions of the concordance and discordance bed level. The results showed at the concordance bed level and junction with a  angle, in both cross-section shapes, the flow separation zone is formed near the bed, with the difference that in a trapezoidal section, its dimension was bigger than the rectangular section. At the  angle of the concordance bed level, this zone did not appear in any sections; but for unequal bed level junction, the separation zone was formed only on the water surface and for the trapezoidal section. In addition, the flow separation zone was not formed at the  discordance junction near the bed, but at the water surface its dimension in trapezoidal shape was more than the rectangular. Besides, the backwater at the upstream of the junction in main canal decreased in trapezoidal shape and in  junction angle.


Aghazadeh Sure, T. and Hemmati, M. (2018a). Simulation of the Effect of Bed Discordance on Flow Pattern at the River Confluence by Flow-3D Model, Iranian Journal of Irrigation and Drainage, 11(5), 785-797. (In Farsi)
Aghazadeh Sure, T. and Hemmati, M. (2018b). Numerical investigation of the effect of junction angle on flow dynamic at the canal junction of concordance and discordance bed level. Journal of Irrigation and Drainage Structures Engineering Research, 19(70), 53-68. (In Farsi)
Best, J. L. (1987). Flow dynamics at river channel confluences: Implications for sediment transport and bed morphology. Recent Developments in Fluvial Sedimentology, 39, 27-35.
Best, J. L. and Reid, I. (1984). Separation zone at open-channel junctions. Journal of Hydraulic Engineering, 110(11), 1588-1594.
Biron, P., Best, J.L. and Roy, A.G. (1996). Effects of bed discordance on flow dynamics at open channel confluences. Journal of Hydraulic Engineering122(12), pp.676-682.
Ghasemzadeh, F. and Kouchakzadeh, S. (2018). Simulation of hydraulic problems in Flow 3D. Tehran: Noavar. (In Farsi)
Gualtieri, C., Filizola, N., Oliveira, M. D., Santos, A. M. and Ianniruberto, M. (2018). A field study of the confluence between Negro and Solimoes rivers. Part 1: Hydrodynamics and sediment transport. Comptes Rendus Geoscience. Journal of Hydrology, Environment, 350(1-2), 31-42.
Khosravinia, P., Hosseinzadeh Dalir, A., Shafai Bajestan, M. and Farsadizadeh, D. (2014). Experimental and numerical investigations of the effect of main channel side slope on flow pattern in right angle confluence of channels. Journal of Soil and Water Science, 24(3), 105-119. (In Farsi)
Konsoer, K. M. and Rhoads, B. L. (2014). Spatial-temporal structure of mixing interface turbulence at two large river confluences. Journal of Environ Fluid Mech, 14(5), 1043-1070.
Lewis, Q. W. and Rhoads, B. L. (2018). LSPIV measurements of two-dimensional flow structure in streams using small unmanned aerial systems: 1. Accuracy assessment based on comparison with stationary camera platforms and in-stream velocity measurements. Water Resources Research, 54(10), 8000-8018.
Ramos, P. X., Schindfessel, L., Pego, J. P. and De Mulder, T. (2019). Influence of bed elevation discordance on flow patterns and head losses in an open-channel confluence. Journal of Water Science and Engineering, 12(3), 235-243.
Rice, S. P., Roy, A. G. and Rhoads, B. L. (2008) River Confluences, Tributaries and the Fluvial Network. John Wiley & Sons, Chichester.
Shabayek, S., Steffler, P. and Hicks, F. E. (2002). Dynamic Model for Subcritical Combining Flows in Channel Junctions. Journal of Hydraulic Engineering, 128(9), 821-828.
Umar, M., Rhoads, B. L. and Greenberg, J. A. (2018). Use of multispectral satellite remote sensing to assess mixing of suspended sediment downstream of large river confluences. Journal of Hydrology, 556, 325-338.
Wang, X.G., Yan, Z.M. and Guo, W.D.   (2007). Three-dimensional simulation for effects of bed discordance on flow dynamics at y-shaped open channel confluences, Journal of hydrodynamics, 19(5), 587-593.
Weber, L. J., Schumate, E. D. and Mawer, N. (2001). Experiments on flow at a 90 open-channel junction. Journal of Hydraulic Engineering, 127(5), 340-350.
Yuan, S., Tang, H., Xiao, Y., Chen, X., Xia, Y. and Jiang, Z. (2018). Spatial variability of phosphorus adsorption in surface sediment at channel confluences: Field and laboratory experimental evidence. Journal of Hydro-Environment Research, 18, 25-36.
Yuan, S., Tang, H., Xiao, Y., Qiu, X. and Xia, Y. (2017). Water flow and sediment transport at open-channel confluences: an experimental study. Journal of Hydraulic Research, 56(3), 333-350.