Numerical and experimental Study of the influence of Wedge Elements on Roughness and Energy dissipation over stepped spillway

Document Type : Original Article

Authors

1 Department Hydraulic Engineering, Faculty of Civil Engineering, Tabriz University, Iran

2 2- Ph.D. Candidate of Hydraulic Structures, Water Engineering Department, Faculty of Civil Engineering, Tabriz University, Tabriz, Iran.

Abstract

In the stepped spillway, the steps, by providing an artificial roughening bed, dissipate the flow of energy more than other types of spillways, which reduce the time and cost of constriction the dam and have been able to attract the designer's attention to these types of spillways. But what is important in this type of spillway, increasing the effectiveness of steps in the rate of energy dissipation. For this reason, the present study intends to consider the addition of wedge-shaped elements on the steps and its impact on the variation of the Darcy roughness, the height of the downstream water flow and, as a result, energy depletion on the stepped spillway. In this regard, first, several shapes of wedge elements are simulated with different layouts using Flow-3D software and then by comparing the results, the proper model from aspect the most energy dissipation has been studied in the laboratory. Experiments were performed on 5 physical models, with changes in wedge layout and discharge rate, and the results were compared with simple stepped spillway. Numerical and experimental results show that the addition of wedge elements on the steps increases the Darcy roughness coefficient and reduces the height of water in the downstream of the spillway and as a result, the energy depletion increases significantly. By reducing the distance between the wedge elements, energy depreciation increases more significantly. Also, there are relationships between the Darcy roughness (f) and the ratio of the critical depth to the step roughness of the stairs (yc / k), that the high accuracy of these relationships (R2 = 0.9-0.98) indicate a significant dependence of the Darcy roughness (f) to the step roughness (k).

Keywords

References

سامانی،ح.م.، نظرزاده،م.ر. 1383. ارزیابی اصول حاکم بر هیدرولیک جریان و طراحی سرریزهای پلکانی. نشریه دانشکده فنی. 38. 2: 339- 347.
سلماسی،ف.، بینا،م.، موسوی جهرمی،س.ح. 1382. ارزیابی افت کارمایه جریان از روی سرریزهای پلکانی با استفاده از شبیه فیزیکی، مجله کشاورزی. 26: 57- 71.
سوری،ن.، مجتهدی،ع. 1393. بررسی الگوی جریان عبوری روی سرریز پلکانی با استفاده از مطالعه عددی و مدل فیزیکی. پایان­نامه کارشناسی ارشد، دانشکده فنی مهندسی عمران، گروه مهندسی آب، دانشگاه تبریز.
فتحی،ا.، بینا،م و موسوی جهرم.، س.ح. 1388. بررسی تاثیر شیب تندآب پایین‌دست تاج بر محل هواگیری طبیعی در جریان غیرریزشی در سرریز پلکانی. نشریه آب ‌و خاک. 23. 3 : 167-156.
محمودی،م.، رستمی راوری،ا. 1391. بررسی اثر نصف کردن ابعاد پله‌ها در سه حالت نسبت 3/1، بر میزان افت کارمایه در شبیه سرریزهای پلکانی. مجله مهندسی منابع آب. 5.   119-107.
Boes,R and Minor,H.E. 2002. Hydraulic design of stepped spillways for RCC dams. Hydropower dams. 9.3: 87–91.
Chamani,M.R and Rajaratnam,N. 1999. characteristics of skimming flow over stepped spillways. journal of hydraulic engineering. 125. 4: 361-368.
Chen,Q., Dai,G and Liu,H. 2002. Volume of fluid model for turbulence numerical simulation of stepped spillway overflow. journal of hydraulic engineering. 128.7: 683-688.
Cheng,X., Chen,Y and Luo,L. 2006. Numerical simulation of air-water two-phase flow over stepped spillways. science in china series E: technological sciences. 49.6: 674-684.
Henderson,F.M.1966. Open channel flow. macmillan, new york.
Ho,D., Boyes,K and Donohoo,S. 2001. Investigation of spillway behavior under increased maximum flood by computational fluid dynamics technique. 14th international proceeding conference of australasian fluid Mechanics.
Rice,C.E and Kadavy,K.C. 1996. Model study of a roller compacted concrete stepped spillway. Journal of hydraulic engineering. 122.6: 292-297.
Roushangar,K., Akhgar,S and Salmasi,F.2018. Estimating discharge coefficient of stepped spillways under nappe and skimming flow regime using data driven approaches. flow measurement and instrumentation. 59: 79-87.
Roushangar,K., Akhgar,S., Salmasi,F and Shiri,J. 2014. Modeling energy dissipation over stepped spillways using machine learning approaches. Journal of hydrology. 508: 254–265
Roushangar,K., Akhgar,S., Salmasi,F and Shiri,J. 2017. Neural networks- and neuro-fuzzy-based determination of influential parameters on energy dissipation over stepped spillways under nappe flow regime. journal of hydraulic engineering.  23. 1: 57–62
Tozzi,M.J. 1992. residual energy in stepped spillways. water power and dam construction. 32-34.
Tabbara,M., Chatila,J and Awwad,R. 2005. Computational simulation of flow over stepped spillways. Computers and structures. 83.27:2215-2224.
Zhong Dong,Q., Xiaoqing,H., Wqnxin,H and Antonio,A. 2009. Numerical simulation and analysis of water flow over stepped spillways. science in china series E: technological sciences.52.7:1958-1965.
Iranian Journal of Irrigation & Drainage
Volume 13, Issue 1 - Serial Number 73
July and August 2019
Pages 78-88

Files

Share

How to cite

Statistics