بررسی عددی میدان جریان روی سرریز اوجی تحت تاثیر شکل تاج و شیب وجه بالادست سرریز

نوع مقاله : مقاله پژوهشی

نویسندگان

1 دانشجوی کارشناسی ارشد مهندسی آب و سازه‌های هیدرولیکی، دانشگاه آیت اله العظمی بروجردی(ره)

2 دانشیار گروه عمران، دانشگاه آیت‌اله‌العظمی بروجردی (ره).

چکیده

در این پژوهش، الگوی جریان سرریز اوجی تحت تاثیر شکل منحنی تاج سرریز و تغییرات شیب وجه بالادست سرریز، با استفاده از نرم‌افزار شبیه­ساز عددی  Flow-3Dمورد ارزیابی قرار گرفت. بدین ترتیب دو سرریز اوجی با تاج بیضوی و الگوی USBR در دو حالت وجه بالادست قائم و مایل با شیب 3H:3V و به­ازای سه هد مختلف، شبیه­سازی شدند و نتایج حاصل از تغییرات پارامترهای موثر نظیر دبی، سرعت و فشار در طول هر یک از سرریز­ها مورد بررسی قرار گرفت. صحت‌سنجی نتایج مدل عددی با نتایج مدل آزمایشگاهی ماینورد نشان داد مدل عددی Flow-3D از توانایی بالایی برای شبیه‌سازی میدان جریان روی سرریز اوجی برخوردار است. مقایسه دبی حاصل از مدل عددی با داده­های آزمایشگاهی، بیان‌گر میانگین خطای محاسباتی زیر سه درصد مدل عددی بود. بررسی میدان فشار نشان داد در ارتفاع هد برابر هد طراحی، فشارها نزدیک فشار اتمسفر می­باشند و فشار منفی روی تاج سرریز ایجاد نشده است اما در هد بالاتر از هد طراحی روی سرریز فشار منفی به‌وجود خواهد آمد. مقدار فشار منفی ایجاد شده در ابتدای تاج سرریز USBR نسبت به مقدار فشار منفی تاج سرریز بیضی شکل، بیش‌تر است و دلیل آن عدم پیوستگی در تاج و جدایی بیش‌تر خطوط جریان از روی آن است. همچنین نتایج نشان داد که سرریز اوجی با تاج بیضی شکل، عملکرد نسبتا بهتری در جریان عبوری از روی سرریز دارد و در این سرریزها امکان عبور دبی­ بیش‌تر با ایمنی بالاتری فراهم می­شود و شیب­دار کردن وجه بالادست سرریز باعث تغییر در ضریب تخلیه و نهایتاً میزان دبی عبوری جریان از روی سرریز می‌شود. 

کلیدواژه‌ها

موضوعات

عنوان مقاله [English]

Numerical Investigation of the Flow Field on the Ogee Spillway under the Influence of the Crest Shape and Slope of the Upstream Face of the Spillway

نویسندگان [English]

  • Mehdi Lak 1
  • Mehdi Komasi 2
1 Department of Civil Engineering, Ayatollah Boroujerdi University.
2 Associate Professor, Department of Civil Engineering, Ayatollah Boroujerdi University
چکیده [English]

In this study, the ogee spillway flow pattern under the influence of the spillway curve shape and upstream slope changes was evaluated using Flow-3D numerical simulator software. Thus, two ogee spillways with elliptical crest and USBR pattern were simulated in two vertical and oblique upstream modes with a slope of 3H:3V and three different heads, and the results of changes in effective parameters such as flow, velocity and pressure in the length of each spillway was examined. Validation of the results of the numerical model with the results of the Maynord experimental model showed that the Flow-3D numerical model has a high ability to simulate the flow field on the ogee spillway. Comparison of flow rate from numerical model with experimental data showed that the average computational error was less than 3% of the numerical model. Examination of the pressure field showed that at the height of the head equal to the design head, the pressures are close to atmospheric pressure and no negative pressure is created on the spillway crest, but at the head higher than the design head, negative pressure will be created on the spillway. The amount of negative pressure created at the beginning of the USBR spillway crest is higher than the negative pressure value of the elliptical spillway crest due to the lack of continuity in the crest and further separation of the flow lines from it.  The results also showed that the ogee spillway with oval crest has a relatively better performance in the flow over the spillway and in these spillways it is possible to pass more discharge with higher safety and sloping the upstream side of the spillway causes a change in the discharge coefficient and finally the flow rate of the spillways.

کلیدواژه‌ها [English]

  • Ogee Spillway
  • Numerical simulation
  • Flow3d
  • Finite Volume
  • Pressure distribution

مراجع

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