ارزیابی قابلیت اطمینان وقوع کاویتاسیون در سرریز تنداب با روش‌های FORM و شبیه‌سازی مونت‌کارلو

نوع مقاله : مقاله پژوهشی

نویسندگان

1 دانشیار گروه مهندسی عمران، دانشگاه سیستان و بلوچستان

2 دکتری مهندسی عمران، دانشگاه سیستان و بلوچستان

چکیده

مهم­ترین عامل در طراحی سرریزهای تنداب، کنترل وقوع کاویتاسیون ناشی از سرعت بالا و فشار منفی جریان می‌باشد. در این تحقیق باتوجه بههزینه‌های بسیار بالای تعمیر و بازسازی سرریز، احتمال وقوع کاویتاسیون با استفاده از روشهای قابلیت اطمینان FORMو شبیه‌سازی مونت‌کارلو، بر روی مدل سرریز تنداب سد داریان، ساخته شده با مقیاس1:50 در مؤسسه تحقیقات آب ایران، بررسی شد. بر این اساس می­توان به­عنوان یک روش کنترلی، برمبنای قابلیت اطمینان که روشی نوین در طراحی است، احتمال وقوع کاویتاسیون در سرریز تنداب را بررسی نمود. با توجه به توابع توزیع احتمال متغیرهای سرعت و فشار که مهم­ترین عامل در وقوع کاویتاسیون هستند و در تابع شرایط حدی استخراج شده، نمایان می‌باشند، اقدام به محاسبه احتمال وقوع کاویتاسیون با استفاده از روش‌های فوق گردید. احتمال خرابی قبل از نصب هواده با استفاده از روش FORM،35 و از روش مونت‌کارلو 40 درصد تعیین گردید. در نتیجه با توجه به هندسه سرریز و حداکثر دبی محتمل، محاسبات نشان می‌دهد که نصب دو عدد هواده که مهم­ترین عامل برای جلوگیری از خرابی ناشی از کاویتاسیون است، اجتناب ناپذیرمی‌باشد.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Assessing the Reliability of Cavitation on Chute Spillway by Using Form and Monte Carlo Simulation Method

نویسندگان [English]

  • Amin Hasanalipour Shahrabadi 1
  • Mehdi Azhdary Moghadam 2
1 Civil Engineering Department, University of Sistan and Baluchestan, Zahedan, Iran.
2 Ph.D. Candidate, Civil Engineering Department, University of Sistan and Baluchestan, Zahedan, Iran.(
چکیده [English]

The most important factor in the design of Chute Spillways is to control the occurrence of cavitation which is due to high velocity and negative pressure of flow. Cavitation occurs when the pressure of the fluid reaches its vapor pressure. In this condition, the fluid is evaporated and bubble is produced inside the liquid. When these bubbles arrive at a region of fluid flow with high pressure, bubbles explode and cause serious damage to structure (Iranian Water Research Institute, 2011). In Iran, the cavitation phenomenon has caused serious damage to the Karun I dam's spillway. The present study, considering the extracted results from laboratory model of chute spillway of Darian dam's spillway, investigates the probability of occurrence of cavitation and examines the reliability of this issue using FORM and Monte Carlo Simulation Method (MCSM). This model is made at a scale of 1:50 in Iranian Water Research Institute. This embankment dam is located in Paveh, Kermanshah province, Iran. The spillway channel width is 68 meters which reaches 42 meters in convergent chute. The slope length of this chute is 300.66 meters, with an angle of 14 degrees. In this laboratory model, in order to cope with the phenomenon of cavitation along the chute, two aerators in the form of deflector were used at the intervals of 211 and 270 at the beginning of chute. In order to study and control the occurrence of cavitation, it is necessary to provide information such as average velocity and pressure applied on the floor in different parts of the structure. Therefore, the flow velocity and the dynamic pressure were measured over it.

کلیدواژه‌ها [English]

  • Chute Spillway
  • Cavitation
  • Reliability
  • FORM
  • Monte Carlo
1-    Ang, A.H.S. and Tang, W., 2007. Probability concept in engineering emphasis on application to civil and environmental engineering. John Wiley & Sons, New York.
 
2-    Anonymous, 1984. Final report of hydraulic system for flood discharge of Karun I dam. Tehran, Iran. Technical Rep. (in Persian).
 
3-    Anonymous, 2011. Final report of hydraulic system for flood discharge of Darian dam. Tehran, Iran. Technical Rep. (in Persian).
 
4-    Chanson, H., 1993. Self-Aerated flows on chutes and spillways. Journal of Hydraulic Engineering, ASCE,119(2), pp.220-243.
 
5-    Chanson, H., 1996. Air bubble entrainment in free-surface turbulent shear flows. Academic Press, London, UK.
 
6-    Chanson, H., 2013. Hydraulics of aerated flows. Journal of Hydraulic Research, IAHR, 51(3), pp.223-243.
 
7-    Chen, S.H., 2015. Hydraulic structures, 1st edition. Springer, Berlin, Germany.
 
8-    Cornell, C.A., 1969. A probability based structural code. Journal of American Concrete Institute 66(12), pp.974-985.
 
9-    Falvey, H.T., 1990. Cavitation in chutes and spillways. United States Department of the Interior, Bureau of Reclamation, A Water Resources Technical Publication, Engineering Monograph No. 42.
 
10- Hasofer, A.M. and Lind, N.C., 1974. Exact and invariant second-moment code format. Journal of Engineering Mechanics, ASCE, 100(1), pp.111-121.
 
11- Kaplan, W., 2002. Advanced calculus, 5th ed, Addison-Wesley.
 
12- Mahdavi, M.A. and Ahadiyan, J., 2015. Evaluation of statistical, empirical, neural networks and neural–fuzzy techniques for estimation of spillway aerators. Journal of Irrigation Science and Engineering, 38(3), pp.51-61. (in Persian).
 
13- Mays, L.W. and Tung, Y.K., 1992. Hydrosystems engineering and management. McGraw-Hill, New York.
 
14- Nowak, A.S. and Collins, K.R., 2000. Reliability of Structures. McGraw-Hill, United States.
 
15- Pettersson, K., 2012. Design of aerators for prevention of cavitation, the Höljes dam. MSc Thesis, Royal Institute of Technology (KTH), Stockholm, Sweden. 33p.
 
16- Pinto, N.L.D.S., Neidert, S.H. and Ota, J.J., 1982. Prototype and laboratory experiments on aeration at high velocity flows. Universidade Federal do Parana, Companhia Paranaense de Energia, Curitiba, Brazil.
 
17- Pinto, N.L.D.S., 1984. Model evaluation of aerators in shooting flow. In the Symposium on Scale Effects in Modelling Hydraulic Structures, Esslingen, Germany.
 
18- Rackwitz, R. and Fiiessler, B., 1978. Structural reliability under combined random load sequence, Computers and Structures, 9(5), pp.489-494.
 
19- Shams Ghahfarokhi, G., Van Gelder, P.H.A.J.M. and Vrijling, J.K., 2008. Probabilistic description of scour hole downstream of flip bucket spillway of large dams. Technical Proc., Int. Conference on Dam and Water for Future (ANCOLD), Gold Coast, Australia.
 
20- Smith, D.J., 2011. Reliability maintainability and risk: practical methods for engineers. Elsevier Ltd.
 
21- Sorensen. J.D., 2004. Structural reliability theory and risk analysis, Institute of Building Technology and Structural Engineering, Aalborg University, Denmark.
 
22- Tung, Y.K. and Mays, L.W., 1980. Risk analysis for hydraulic design. Journal of Hydraulic Engineering, ASCE, 106(5), pp.93-913.
 
23- Vrijling, J.K., 2001. Probabilistic design of water defence systems in the Netherlands. Journal of Reliability Engineering and System Safety, 74(3), pp.337-344.
 
24- Yen, B.C., Cheng, S.T. and Melching, C.S., 1986. First order reliability analysis, Water Resources Publications, Littleton, Co, pp.1-36.
 
25- Yen, B.C. and Tung, Y.K., 1993. Reliability and uncertainty analyses in hydraulic design, ASCE, New York.
 
26- Zandi Goharrizi, F., 2010. Prediction of cavitation in smooth spillway using fuzzy logic, MSc Thesis, University of Sistan and Baluchestan, Zahedan, Iran. 158p. (in Persian).