بررسی آزمایشگاهی استهلاک انرژی در شیب‌شکن‌‌های قائم مجهز به صفحه مشبک قائم با واگرایی تدریجی در پایین‌دست

نوع مقاله : مقاله پژوهشی

نویسندگان

1 دانشجوی دکترای عمران آب و سازه های هیدرولیکی ، دانشکده عمران، دانشگاه تبریز، ایران

2 استاد داشکده عمران - دانشگاه تبریز، تبریز، ایران

3 دانشیار گروه مهندسی عمران، دانشکده فنی و مهندسی، دانشگاه مراغه، مراغه، ایران

چکیده

در مطالعه حاضر برای افزایش راندمان استهلاک انرژی جریان، اثر توامان شیب شکن قائم، واگرایی تدریجی و صفحات مشبک قائم مورد بررسی قرار گرفت. آزمایش‌ها در یک فلوم آزمایشگاهی افقی با مقطع مستطیلی، با دو ارتفاع شیب شکن قائم و در نسبت‌های واگرایی دیواره 0/5 تا 1 ،نسبت تخلخل صفحات مشبک 40 %و 50 %و محدوده عدد فرود 0/68 تا0/92 انجام گرفت. نتایج نشان داد که استفاده از صفحات مشبک و واگرایی دیواره ها باعث افزایش استهلاک انرژی و کاهش عمق استخر و عمق پایین دست می‌گردد. بکارگیری دیواره واگرایی، صفحات مشبک و تاثیر استفاده همزمان از صفحات مشبک و دیواره واگرایی به ترتیب باعث افزایش 25 ،44 و 48 درصدی راندمان استهلاک انرژی می‌گردد. نسبت تخلخل صفحات مشبک تاثیر چندانی بر روی استهلاک انرژی ندارند ولی باعث کاهش عمق استخر و افزایش عمق پایین دست می‌گردد. در شرایط هیدرولیکی یکسان، با افزایش ارتفاع شیب شکن میزان استهلاک انرژی جریان در اثر شدت برخورد بیشتر جت جریان عبوری از روی شیب شکن با کف پایین دست آن افزایش و عمق استخر کاهش می‌یابد. با افزایش دبی، پرش هیدرولیکی تشکیل شده در بالادست صفحات مشبک با نسبت تخلخل 40 درصد از نوع مستغرق بوده و به بالادست حرکت می‌کند. این در حالی است که در صفحات مشبک 50 درصد پرش ایجاد شده بصورت آزاد بوده و به سمت پایین دست حرکت می‌کند.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Experimental study of Energy Dissipation at Vertical Drops Equipped to Vertical Screen with Gradually Expanding at the Downstream

نویسندگان [English]

  • Behnam Nayebzadeh 1
  • Mohammad ali Lotfollahi-yaghin 2
  • Rasoul Daneshfaraz 3
1 Civil Engineering Faculty, University of Tabriz, Tabriz, Iran
2 Professor, Faculty of Civil Engineering, University of Tabriz, Tabriz, Iran
3 Associate Professor, Department of Civil Engineering, Faculty of Engineering, University of Maragheh, Maragheh, Iran.
چکیده [English]

 In the present study, the effect of vertical drop, gradually expanding and vertical screens are investigated to increase the energy dissipation efficiency of the flow. The experiments were carried out in a horizontal laboratory flume with a rectangular cross section, two vertical drop heights, and the wall expanding ratios of 0.5 to 1, the porosity ratio of the screens of 40% and 50%, and the range of Froude number of 0.86-0.92. The results showed that the use of screens and the expansion of the walls would increase energy dissipation and decrease the pool and downstream depths. The application of expanding wall, screens and the effect of simultaneous use of screens and expanding walls increases the efficiency of energy dissipation by 25, 44 and 48 percent, respectively. The porosity ratio of the screens is not much efficient in energy dissipation, but it reduces the pool depth and increases the downstream depth. Under the same hydraulic conditions, with increasing drop height, the energy dissipation rate due to the higher impact intensity of the jet passing through the drop or its downstream floor increases and the pool depth decreases. By increasing the discharge, the hydraulic jump formed in the upstream of the screens with a porosity ratio of 40% is submerged and moves upstream. However, in screens, 50% of the jump is free and moves downstream.

کلیدواژه‌ها [English]

  • Vertical drop
  • Energy dissipation efficiency
  • Gradually Expanding
  • Screens
  • Pool depth
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