بررسی آزمایشگاهی پرش هیدرولیکی در تنگ شدگی ناگهانی با بستر زبر

نوع مقاله : پژوهشی اصیل (کامل)

نویسندگان
رسول دانشفراز 1
امیر نجیبی 2
1 استاد، گروه مهندسی عمران، دانشکده فنی و مهندسی، دانشگاه مراغه، مراغه، ایران
2 دانشجوی آب و سازه های هیدرولیکی . دانشکده فنی و مهندسی، دانشگاه مراغه
10.22034/22.6.65
چکیده
یکی از مهم­ترین معضلاتی که در پایین­دست سازه­های هیدرولیکی وجود دارد، انرژی مخرب جنبشی جریان است. همواره کارشناسان سعی در طراحی مناسب و کاهش اثر این نیروی مخرب در پایین­دست سازه­ های هیدرولیکی را دارند. تحقیق حاضر با هدف بررسی زبری کف مقطع تنگ­شدگی برمیزان استهلاک انرژی درجریان فوق بحرانی در کانال مستطیلی شکل انجام شد. سه نوع تنگ­ شدگی با عرض­های 5، 10 و 15 سانتی­متر و سه زبری با قطرهای متوسط0.8 ,1.28 ,2.08 D50= سانتی­متر و محدوده عدد فرود 7.5≤ FrA≤ 2.5 و انقباض نسبی 0.5 تا 0.83 مورد بررسی قرار گرفت. نتایج آزمایشگاهی نشان داد که با افزایش عدد فرود جریان بالادست، استهلاک انرژی نسبی بالا­دست ( ΔE/EA ) افزایش می­یابد. همچنین با بکارگیری زبری در کف هرسه مقطع تنگ­شدگی مشاهده شد که استهلاک انرژی بطور چشم­گیری افزایش یافت بطوریکه بیشترین استهلاک انرژی با 78.35 درصد افزایش مربوط به تنگ­شدگی 15 سانتی­متر و کمترین استهلاک انرژی با 43.35 درصد افزایش مربوط به تنگ­شدگی 5 سانتی­متری می­باشد. روابط استخراج شده برای تخمین استهلاک انرژی نسبی نشان داد که نتایج آن با داده­های آزمایشگاهی مطابقت خوبی با ضریب همبستگی 0.927 و خطای جذر میانگین مربعات نرمال شده 0.2 دارند.

کلیدواژه‌ها

موضوعات

عنوان مقاله English

Experimental Investigation of Hydraulic Jump in Sudden Contraction with Rough Bed

نویسندگان English

R. Daneshfaraz 1
A. Najibi72 2
1 Professor, Department of Civil Engineering, Faculty of Engineering, University of Maragheh, Maraghehو Iran.
2 M.Sc. Student, Department of Civil Engineering, Faculty of Engineering, University of Maragheh, Maragheh, Iran
چکیده English

One of the most important problems in downstream hydraulic structures is the destructive kinetic energy of the flow. Experts always try to properly design and reduce the effect of this destructive force on the downstream of hydraulic structures in rectangular channel. The aim of this study was to investigate the effect of sudden contraction with the rough bed of contracted section on the relative energy dissipation in the supercritical flow. Three types of constrictions with widths of 5, 10 and 15 cm and three roughnesses with average diameters of D50=0.8, 1.28 and 2.08 cm and range of Froude number 2.5 to 7.5 and relative contracting 0.5 to 0.83 was examined. Experimental results showed that with increasing the upstream Froude number, the upstream relative energy dissipation (ΔE/EA) increases. Also, by applying roughness to the bed of all three sections of contracting, it was observed that energy dissipation increased significantly so that the highest energy dissipation with 78.35% increase related to 15 cm contracting and the lowest energy dissipation with 43.35% increase related to the contracting of 5 cm. The relationships extracted to estimate the relative energy dissipation showed that the results are in good agreement with the experimental data with a correlation coefficient of 0.927 and a normalized square absorption line of 0.02.

کلیدواژه‌ها English

Relative energy dissipation
Sudden contraction
Rough bed
Froude number
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مهندسی عمران مدرس
دوره 22، شماره 6
آذر و دی 1401
صفحه 65-77