Simulation of the Effect of Bed Discordance on Flow Pattern at the River Confluence by Flow-3D Model

Document Type : Original Article

Authors

Assistant professor of water engineering, Urmia University., Urmia., Iran

Abstract

The dynamics of flow in river confluences are complex; in particular, immediately at the downstream of the junction, the flow creates a separation zone with secondary re-circulation patterns. This study aims at examining the influence of the relative bed discordance (z/y3) and discharge ratio (Qr=Q2/Q3) on flow dynamics in river confluence by Flow-3D model. To achieve this goal four discharge ratios (Qr= 0.2, 0.33, 0.5, 0.67) and four bed discordance ratios (z/y3=0, 0.1, 0.2, 0.3) were considered in a 90 degree junction. In this research, the parameters such as separation zone dimension, flow pattern, mixing layer, water level and velocity pattern were studied. The results showed that changing bed level affects the flow pattern in the junction; so that the dimensions of the created separation zone was different for concordance and discordance bed level. The separation zone near the bed observed only for same bed level junction and it was not occurring at the unequal bed level. By increasing the bed discordance, ration the width and length of separation zone increases and decreases, respectively. Also, the water level in the main channel increased (at the upstream of the junction) and in the tributary flume decreased with increasing the bed level. In addition, the energy turbulence at the confluence increases by increasing the bed level that its amount in unequal bed level junction (z/y3=0.3) is 1.34 times of equal bed level

Keywords

References

قبادیان،ر. 1385. بررسی الگوی جریان، فرسایش و رسوب­گذاری در تلاقی رودخانه­ها. رساله دکتری سازه­های آبی، دانشکده مهندسی علوم آب، دانشگاه شهید چمران اهواز.
قبادیان،ر.، شفاعی بجستان،م و موسوی جهرمی،س.ح. 1385. بررسی آزمایشگاهی جداشدگی جریان در محل تلاقی رودخانه‌ها برای شرایط جریان زیر بحرانی. مجله تحقیقات منابع آب ایران. 2.2 :67-77.
محمدی،س و شفاعی بجستان،م. 1391. بررسی تاثیر شعاع گردشدگی لبه پایین دست کانال اتصال بر تغییرات تراز بستر. مجله پژوهش آب ایران. 6.10 : 123-130.
موسوی جهرمی،س.ح و گودرزی­زاده،ر. 1390. شبیه­سازی عددی الگوی جریان در تلاقی کانال­های باز. مجله علوم و مهندسی آبیاری. 34. 2: 70-61.
همتی،م. 1387. بررسی تاثیر اختلاف رقوم بستر دوکانال بر میزان آبشستگی در محل تلاقی رودخانه­ها. پایان­نامه کارشناسی ارشد، دانشکده مهندسی علوم آب، دانشگاه شهید چمران اهواز.
همتی،م و شفاعی بجستان،م. 1388. بررسی آزمایشگاهی الگوی فرسایش و رسوب­گذاری در محل تلاقی رودخانه­های غیرهمکف. مجله تحقیقات منابع آب ایران. 5.1 :69-77.
Best,J.L. 1987. Flow dynamics at river channel confluences: implications for sediment transport and bed morphology. In: Ethridge, F.G., Flores, R.M., Harvey, M.D. (Eds.), Recent Developments in Fluvial Sedimentology. Special Publications of the Society of Economic Paleontologists and Mineralogists (SEPM). 39: 27-35.
Best,J.L. 1988. Sediment transport and bed morphology at river channel confluences. Sedimentology. 35.3: 481-498.
Best, J.L. and Reid, I. 1984. Separation zone at open-channel junctions. Journal of Hydraulic Engineering. 110.11: 1588-1594.
Best,J.L and Roy,A.G. 1991. Mixing- layer distortion at the confluence of channels of different depth. Nature. 350: 411-413.
Biron,P.M., Roy,A.G., Best,J.L and Boyer,C.J. 1993. Bed morphology and sedimentology at the confluence of unequal depth channels. Geomorphology. 8:2-3. 115-129.
Biron,P.M., Best,J and Roy,A.G. 1996. Effect of  bed discordance on flow dynamics at open channel confluences. Journal of  Hydraulic Engineering.  122:12. 676 - 682.
Boyer,C., Roy,A.G and Best,J.L. 2006. Dynamics of a river channel confluence with discordant beds: Flow turbulence, bed load sediment transport, and bed morphology. Journal of Geophysical Research-Earth. 111.F4:1-22.
De Serres,B., Roy,A.G., Biron,P and Best,J.L. 1999. Three-dimensional flow structure at a river channel confluence with discordant beds. Geomorphology 26.4: 313–335.
Ghobadian,R and Basiri,M. 2015. The effect of downstream curved edge on local scouring at 60 degree open channel junction using SSIIM1 model. Ain Shams Engineering Journal. 7:2. 543-552.
Guillén-Ludeña,S., Franca,M.J., Cardoso,A.H and Schleiss,A.J. 2016. Evolution of the hydro morphodynamics of mountain river confluences for varying discharge ratios and junction angles. Geomorphology. 255: 1-15.
Nazari-Giglou,A., Jabbari- Sahebari,A., Shakibaeinia,A and Borghei,S. M. 2016. An Experimental Study of Sediment Transport in Channel Confluences. International Journal of Sediment Research. 31:1.87-96.
Riley,J.D., Rhoads,B.L., Parsons,D.R. and Johnson,K.K. 2015. Influence of junction angle on three-dimensional flow structure and bed morphology at confluent meander bends during different hydrological conditions. Earth Surface Process and Landforms. 40:2.252-271.
Rhoads,B.L and Sukhodolov,A.N. 2008. Lateral momentum flux and the spatial evolution of flow with in a confluence mixing interface. Water Resource Research. 44:8.1-17.
Rooniyan,F. 2014. The Effect of confluence angle on the flow pattern at a rectangular open-channel. Journal of Engineering, Technology and Applied Science Research. 4:1.576-580.
Roy,A.G., Roy,R., Bergeron,N. 1988. Hydraulic geometry and changes in flow velocity at a river confluence with coarse bed material. Earth surface Processes and Landforms. 13:7.583 – 598.
Roy,A.G and Bergeron,N. 1990. Flow and particle paths at a natural river confluence with coarse bed material. Geomorphology. 3:2.99-112.
Shafai-Bejestan,M and Hemmati,M. 2008. Scour depth at river confluence of unequal bed level. Journal of applied sciences. 8:9.1766-1770.
Wang,X. G and Yan,Z.M. 2007. Three-dimensional simulation for effects of bed discordance on flow dynamics at y-shaped open channel confluences. Journal of hydraodynamics. 19:5.587-593.
Yuan,S., Tang,H., Xiao,Y., Qiu,X., Zhang,H and Yu,D. 2016. Turbulent flow structure at a 90-degree open channel confluence: Accounting for the distortion of the shear layer. Journal of Hydro-environment Research. 12: 130-147.
Sukhodolov,A.N and Rhoads,B.L. 2001. Field investigation of three-dimensional flow structure at stream confluences: 2. Turbulence. Water Resource Research. 37: 2411–2424.
 
 
 
Iranian Journal of Irrigation & Drainage
Volume 11, Issue 5 - Serial Number 65
January and February 2018
Pages 785-797

Files

Share

How to cite

Statistics