تأثیر ارتفاع و شیب تاج ‌سرریز‌های مستغرق بر الگوی فرسایش و رسوب در قوس 90 درجه تند

نوع مقاله : مقاله پژوهشی

نویسندگان

1 گروه مهندسی آب،دانشکده کشاورزی و منابع طبیعی، دانشگاه ارومیه، ارومیه، ایران.

2 گروه مهندسی آب، دانشکده کشاورزی و منابع ظبیعی، دانشگاه ارومیه، ارومیه، ایران

3 گروه مهندسی آبیاری و آبادانی، دانشکده مهندسی و فناوری کشاورزی، دانشگاه تهران،کرج، ایران

4 گروه مهندسی عمران، محیط زیست و معماری، دانشکده فنی مهندسی، دانشگاه پادوا، پادوا، ایتالیا

چکیده

سرریزهای مستغرق سازه­هایی با ارتفاع کوتاه هستند که کاملاً زیر سطح آب قرار داشته و جهت بهبود شرایط کشتیرانی، ایجاد زیستگاه آبزیان، کنترل جابجایی قوس‌ها و ... احداث می‌شوند. هدف این تحقیق ارزیابی کارایی سرریزهای مستغرق بر الگوی فرسایش و رسوبگذاری در قوس 90 درجه تند می‌باشد. به‌منظور رسیدن به این هدف مجموعه­ای از سرریزها با ارتفاع نسبی 30 و 70 درصد و شیب تاج صفر و 7 درصد در دیواره قوس خارجی احداث شدند. زاویه، طول و فاصله بین سرریزها ثابت در نظر گرفته شد. نتایج نشان داد که سرریزهای با ارتفاع نسبی 70 درصد و شیب تاج صفر بهترین عملکرد را در حفاظت بستر نزدیک دیواره قوس خارجی داشت. با احداث این سازه­ها در قوس، 7 درصد رسوبگذاری نزدیک دیواره خارجی در مقطعی که منطبق بر محل ماکزیمم آبشستگی در حالت شاهد بود، صورت گرفت. تغییر در ارتفاع و شیب تاج سرریز مستغرق اثر قابل‌ملاحظه‌ای بر کاهش ماکزیمم ارتفاع نسبی تپه رسوبی نداشت و فقط در فرود 43/0 به‌طور متوسط ماکزیمم ارتفاع نسبی تپه رسوبی 10 درصد کاهش پیدا کرد. علاوه بر آن، با افزایش ارتفاع و شیب تاج سرریز­های مستغرق ماکزیمم عمق نسبی آبشستگی در دماغه سرریز سوم به ترتیب 11 درصد افزایش و 6 درصد کاهش پیدا کرد.

کلیدواژه‌ها


عنوان مقاله [English]

The Effect of Height and Crest Slope of the Submerged Weirs on Erosion and Sedimentation Pattern in a 〖90〗^o Sharp Bend

نویسندگان [English]

  • MOHSEN SALEHZADEH 1
  • Mohammad Hemmati 2
  • Mehdi Yasi 3
  • STEFANO LANZONI 4
1 Department of Water Engineering, faculty of agriculture and natural resources, Urmia University, Urmia, Iran
2 Department of Water Engineering, faculty of irrigation and natural resources, Urmia University, Urmia, Iran
3 Department of Irrigation and Reclamation Engineering, faculty of agricultural engineering and technology, University of Tehran, Karaj, Iran
4 Department of Civil, Environmental , and Architectural Engineering ICEA, faculty of engineering, University of Padua, Padua, Italy.
چکیده [English]

Submerged weirs are short-height structures that are completely beneath the water surface and are constructed to improve shipping conditions, create aquatic habitats, control the movement of bends, etc. The purpose of this study was to evaluate the patterns of erosion and sedimentation at a 90o sharp bend. To achieve this goal, a series of weirs with the relative heights of 30% and 70% and crest slopes of 0 and 7% were constructed on the outer wall of the bend. The angle, length, and distance between weirs were kept constant. The results showed that bendway weirs with a relative height of 70% and a flat crest slope had the best performance in protecting the bed near the outer bend wall. With the construction of these structures in the bend, 7% of sedimentation was done near the outer wall at a cross-section corresponding to the maximum scour location in the unstructured state. Changes in the height and crest slope of the bendway weir did not have a significant effect on reducing the maximum relative height of point-bar, and only at Froude number of 0.43 the average maximum relative point-bar height decreased by 10%. Moreover, with increasing the height and crest slope of the weirs, the maximum relative scours depth at the nose of the third weir increased by 11% and decreased by 6%, respectively.

کلیدواژه‌ها [English]

  • Inner wall
  • Outer wall
  • Point-bar
  • scour
  • Thalweg
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