بررسی آزمایشگاهی هیدرودینامیک جریان در آبراهه‌های مرکب پیچان با دیواره سیلاب‌دشت هم‌راستا

نوع مقاله : مقاله پژوهشی

نویسندگان

1 گروه علوم و مهندسی آب، دانشکده کشاورزی، دانشگاه فردوسی مشهد، مشهد، ایران

2 گروه علوم و مهندسی آب، دانشکده کشاورزی، دانشگاه فردوسی مشهد، مشهد، ایران.

چکیده

پیش­بینی رفتار جریان در قوس رودخانه­های مرکب پیچانی در برنامه­های حفاظت سواحل (الگوی انتقال و ته­نشست رسوبات)، انتشار آلودگی و کنترل سیلاب کاربردی و دارای اهمیت زیادی می­باشد. ازاین‌رو؛ هیدرودینامیک جریان در آبراهة مرکب - پیچان با ضریب خمیدگی ثابت 3/1، و هم­راستایی دیوارة سیلاب­دشت با کانال اصلی در دو عمق نسبی 3/0 و 55/0 با استفاده از مدل آزمایشگاهی بررسی شد. به دلیل ساختار سه­بعدی جریان در قوس آبراهه، تجزیه‌وتحلیل داده­ها در هفت مقطع عرضی با زوایای صفر، 30 و 60 درجه نسبت به رئوس قوس با استفاده از سرعت­سنج ADV در صفحه­های مشبک با ابعاد cm2 3×3 و عمود بر جریان انجام گرفت. نتایج نشان داد؛ گرادیان هر سه مؤلفه سرعت در عمق نسبی 3/0 بیش­تر از 55/0 است که نشان از قدرت بیشتر گرداب­ها و شدت آشفتگی در عمق نسبی کمتر دارد. نسبت سرعت متوسط در ساحل خارجی سیلاب­دشت به‌سرعت متوسط کل مقطع، مشابه ساحل داخلی، تابع عمق نسبی جریان بوده و به ترتیب کمتر و بیشتر از یک است. به همین علت، جریان در سیلاب­دشت خارجی بر خلاف سیلاب­دشت داخلی اثر کاهنده بر سرعت جریان در آبراهه اصلی دارد. همچنین نسبت سرعت متوسط جریان در آبراهه اصلی به‌سرعت متوسط کل به­ازای افزایش عمق نسبی تقریبی از 3/0 به 55/0 کاهش‌یافته و به یک نزدیک می­گردد. تنش رینولدز  در نزدیک بستر آبراهه اصلی، دارای مقادیر بیشینه و مثبت بوده و با فاصله گرفتن از بستر، با روندی کاهشی، به مقدار منفی رسیده و کمینه خود را در نزدیکی سطح جریان نشان می­دهد. همچنین در لبه دشت­های سیلابی نیز مقدار این پارامتر موضعی افزایش می­یابد.

کلیدواژه‌ها

عنوان مقاله [English]

Experimental Study of Flow Hydrodynamics in Meandering Compound Channels with Parallel Floodplain Wall

نویسندگان [English]

  • sobhan moradi 1
  • kazem esmaili 2
  • saeed reza khodashenas 2
1 Department of Water Science and Engineering, Faculty of Agriculture, Ferdowsi University of Mashhad, Mashhad, Iran.
2 Department of Water Science and Engineering, Faculty of Agriculture, Ferdowsi University of Mashhad, Mashhad, Iran.
چکیده [English]

Predicting the flow behavior in the arch of meandering compound channels has a great importance in coastal protection programs (sediment transport and deposit pattern), pollution propagation and flood control. Therefore; the hydrodynamics of the flow in the composite-meander channel with a constant sinuosity factor 1.3, and at two relative depths 0.3 and 0.55 were investigated using a laboratory model. Due to the three-dimensional structure of the flow in the channel bend, the data were analyzed in seven cross sections with angles of zero, 30 and 60 degrees to the vertices of the bending apex using an ADV velocity-meter in lattice plates with dimensions 3*3 cm2 and perpendicular to the flow. The results showed that the gradient of three components of velocity at relative depths 0.3 are greater than 0.55 which shows more vortex power and intensity of turbulence in less amount of relative depth. average velocity ratio on the outer beach of the floodplain to the average velocity of the whole section, similar to the inner beach, has been a function of the relative depth of the flow, and is less and more than one, respectively. For this reason, the flow in the outer floodplain, unlike the inner floodplain, has a reducing effect on the flow velocity in the main channel. Also, as the relative depth increases from 0.3 to 0.55, the ratio of the average flow velocity in the main channel to the total average velocity decreases and approaches one. Reynolds stress () had maximum and positive values near the main channel bed, and by moving away from the bed, it has reached a negative value and it shows its minimum amount near the flow surface. The value of this local parameter also increases at the edge of floodplains.

کلیدواژه‌ها [English]

  • River Bend
  • Momentum Transmission
  • Turbulent Flow
  • Compound Meander Channel

مراجع

Al-Khatib, I. A., Abaza, Kh. A. and Fkhidah, I. A. (2014). Prediction of zonal and total discharges in smooth straight prismatic compound channels using regression modeling. Flow Meas. Instrum. 38, 40-48.
Bennett, S. J. and J. L. Best. (1995). Mean flow and turbulence structure over fixed, two-dimensional dunes: Implication for sediment transport and bed form stability. Sedimentology, 42, 491-513.
Da Silva, A. M. F. (1995). Turbulent flow in sine-generated meandering channels. Thesis (Ph.D.), Department of Civil Engineering, Queen's University, Kingston Canada.
Da Silva, A.M.F. (2006). On why and how do rivers meander. Journal of Hydrauic Research, 44(5), 579–590.
Dupuis, V., Proust, S., Berni, C. and Paquier, A. (2017). Mixing layer development in compound channel flows with submerged and emergent rigid vegetation over the floodplains. Experiments in Fluids, 58(4), 30.
Ervine, D.A., Babaeyan-Koopaei, K. and Sellin, R.H.J. (2000). Two- dimensional solution for straight and meandering overbank flows, Journal of Hydraulic Engineering, ASCE, 126(9), 653-669.
Hamidifar, H. and Omid, M.H. (2013). Floodplain vegetation contribution to velocity distribution in compound channels. Journal of Civil Engineering and Urbanism. 3(6), 357-361.
Hamidifar, H., Omid, M. H., & Keshavarzi, A. (2016). Kinetic energy and momentum correction coefficients in straight compound channels with vegetated floodplain. Journal of hydrology, 537, 10-17. J. Fluid Mech. 222, 617-646.
Kang H. and choi S. U. (2005). Reynolds stress modelling of rectangular open channel flow. International Journal for Numerical Methods in Fluids. 51(11), 1319-1334.
Liu, C., Wright, N., Liu, X. and Yang, K. (2014). An analytical model for lateral depth-averaged velocity distributions along a meander in curved compound channels, Advances in Water Resources, 74, 26–43.
Mohanta, A. and Patra, K.C. (2019). MARS for Prediction of Shear Force and Discharge in Two-Stage Meandering Channel. Journal of Irrigation and Drainage Engineering, 145(8), 04019016.
Mohanty, P.K. (2019). Flow and its distribution in wide meandering compound channels. Journal of Hydrology, 575,115-130.
Myers, W. (1978). Momentum transfer in a compound channel. Journal of Hydraulic Research. 16(2), 139-150.
Naghavi, M., Mohammadi, M.A and Mahtabi, G. (2020). The intensity of turbulence and shear stress of the wall in the twisted composite channel due to the change of the bending coefficient. Modeling in Engineering, 18(60), 53-69. (In Farsi)
Nezu I. and Rodi W. (1985). Experimental Study on Secondary Currents in Open- channel Flow. 21st IAHR Congress, Melbourne Australia. 115-119.
Pan, Y., Li, Z., Yang, K. and Jia, D. (2019). Velocity distribution characteristics in meandering compound channels with one-sided vegetated floodplains. Journal of Hydrology. 578, 124068.
Parsaie, A. (2016). Analyzing the distribution of momentum and energy coefficients in compound open channel. Modeling Earth Sys. Environ. 2, 1-5.
Shahsavari, H., Khodashenas, S, R., Esmaili, K. (2020). Investigation of Relative Depth Effect on Flow Characteristics in Meandering Compound Channel. Iranian Journal of Soil and Water Research. 51(8), 2111-2124. (In Farsi)
Sellin, H. J. (1964). A Laboratory Investigation into the Interaction between Flow in the Channel of a River and That of Floodplain. La Houille Blanche, 7, 793-801.
Shiono, K. and Knight, D. W. (1991). Turbulent open-channel flows with variable depth across the channel.
Shiono, K., and Muto, Y. (1998). Complex flow mechanisms in compound meandering channels with overbank flow. Journal of fluid mechanics, 376, 221-261.
Shiono, K., Chan, T.L., Spooner, J., Rameshwaran, P. and Chandler, J.H., (2009). The effect of floodplain roughness on flow structures, bedforms and sediment transport rates in meandering channels with overbank flows: Part I. Journal of Hydraulic Research, 47(1), 5-19.
Tominaga, A., Nezu, L., Ezaki, K. and Nekagawa, H. (1989). Three-dimensional turbulent structure in straight open channel flows. Journal of Hydraulic Research. 27(1), 149-173.
Yan, X., Rennie, C. D., & Mohammadian, A. (2020). A three-dimensional numerical study of flow characteristics in strongly curved channel bends with different side slopes. Environmental Fluid Mechanics, 20, 1491-1510.
Yang, K. J., Cao, S.Y. and Knight, D. W. (2007). Flow patterns in compound channels with vegetated floodplains, Journal of Hydraulic Engineering. 133(2), 148-159.
Yonesi, H.A., Omid, M.H. and Ayyoubzadeh, S.A. (2013). The hydraulics of flow in non-prismatic compound channels. Journal of Civil Engineering and Urbanism. 3(6), 342-356.
Zahiri, A., & Najafzadeh, M. (2018). Optimized expressions to evaluate the flow discharge in main channels and floodplains using evolutionary computing and model classification. International Journal of River Basin Management, 16(1), 123-132.
Zahiri, A., Abdolmajidi, H., Ghorbani Koohi Kheili, S. and Dehghani, A. (2012). Simulation of lateral velocity distribution in rivers using Finite Elements Method (Case study: Berentine hydrometric station in Minab River). Journal of Water and Soil Conservation, 19(2), 63-80. (In Farsi)
 
 
تحقیقات آب و خاک ایران
دوره 53، شماره 1
فروردین 1401
صفحه 189-203

فایل ها

هم رسانی

ارجاع به این مقاله

آمار