شبیه‌سازی عددی استهلاک انرژی در مواجهه با انقباض هلالی‌شکل مسیر جریان

نوع مقاله : مقاله پژوهشی

نویسندگان

1 استاد، گروه مهندسی عمران، دانشکده فنی و مهندسی، دانشگاه مراغه

2 گروه عمران، دانشکده فنی و مهندسی، دانشگاه مراغه، مراغه، ایران

3 دانشجوی کارشناسی ارشد گروه عمران آب و سازه های هیدرولیکی، دانشکده فنی و مهندسی، دانشگاه مراغه، مراغه، ایران

چکیده

از روش­های کنترل و کاهش انرژی جریان، استفاده از سازه­های مستهلک­کننده انرژی و تشکیل پرش هیدرولیکی است. یکی از انواع این سازه­ها، المان­های تنگ­شدگی در مسیر جریان است که منجر به افت انرژی جریان عبوری می­شود. در تحقیق حاضر به بررسی عددی تأثیر تنگ­شدگی هلالی­شکل به­عنوان سازه مستهلک‌کننده انرژی در مسیر جریان فوق­بحرانی با استفاده از نرم‌افزار FLOW-3D پرداخته شده است. با بررسی نتایج حاصل از شبیه­سازی، مدل­ آشفتگی RNG به­علت برخورداری از دقت بیشتر و پائین‌بودن درصد خطای نسبی و خطای مطلق نسبت به­سایر مدل­ها، از میان 4 مدل­ آشفتگی RNG، k-ε، k-ω و LES انتخاب شد. در این مطالعه، دامنه عدد فرود بعد از دریچه به­عنوان موثرترین پارامتر بدون­بعد در استهلاک انرژی از 8/2 تا 5/7 تغییر کرده و مقادیر تنگ­شدگی از طرفین 5 و 5/7 سانتی­متر می­باشد. نتایج حاکی از آن است که در تمامی حالات استفاده از تنگ­شدگی هلالی­شکل، استهلاک انرژی ناشی از تنگ­شدگی به­ترتیب در تنگ­شدگی 5 و 5/7 سانتی­متر براساس افت انرژی نسبت به بالادست 62/24% و 84/29% و نسبت به پائین­دست 14/46% و 42/48% بیشتر از پرش کلاسیک آزاد است. هم‌چنین با بررسی نتایج به­دست آمده مشاهده شد که تنگ­شدگی هلالی­شکل در مقایسه با انقباض ناگهانی، حاصل از مطالعات محققین پیشین، عملکرد بهتری از نظر میزان افت انرژی دارد. براساس نتایج حاصل از شبیه­سازی با افزایش عدد فرود بالادست، افت انرژی نسبت به بالادست و پائین­دست تنگ­شدگی هلالی­شکل افزایش یافته به‌طوری‌که استفاده از المان­های تنگ­شدگی باعث کاهش عدد فرود در پائین­دست مقطع تنگ­شدگی در بازه 6/1 الی 3/2 شده است.

کلیدواژه‌ها


عنوان مقاله [English]

Numerical Simulation of Energy Dissipation in Crescent-Shaped Contraction of the Flow Path

نویسندگان [English]

  • Rasoul Daneshfaraz 1
  • Ehsan Aminvash 2
  • Hamidreza Abbaszadeh 3
1 Professor, Department of Civil Engineering, Faculty of Engineering, University of Maragheh, Iran.
2 M.sc student, Department of Civil Engineering, Faculty of Engineering, University of Maragheh, Iran.
3 M.sc student, Department of Civil Engineering, Faculty of Engineering, University of Maragheh, Iran
چکیده [English]

One of the methods of controlling and reducing flow energy is to use energy dissipating structures through formation of hydraulic jumps. One of these types of structures is the constriction elements in the flow path, which leads to a decrease in the energy of the passing flow. In the present study, the effect of crescent-shaped contraction as an energy dissipating structure in the supercritical flow path has been investigated using FLOW-3D software. Examining the simulation results, the RNG model among the four turbulence models, RNG, k-ε, k-ω and LES was selected due to its higher accuracy and lower relative error and absolute error percentage. In this study, the amplitude of the Froude number after the gate as the most effective dimensionless parameter in energy dissipation varied from 2.8 to 7.5 and the values of stenosis on both sides are 5 and 7.5 cm. The results show that in all cases of using the crescent-shaped contractions, the energy dissapation in 5 and 7.5 cm contractions are respectively 24.62% and 29.84% more than the ones in the classic free jump, based on the energy drop relative to the upstream, and 46.14% and 48.42% more, based on the energy drop relative to the downstream. Also, by reviewing the previous researchs, it was found that the crescent-shaped contractions have a better performance in terms of energy loss compared to the sudden contraction. Based on the simulation results, with increasing the upstream Froude number, the energy dissipation is increased relative to the upstream and downstream of crescent-shaped contraction, so that the use of contraction elements reduces the downstream Froude number of the contracted section in the range of 1.6 to 3/2.

کلیدواژه‌ها [English]

  • energy dissipation
  • Crescent-shaped contraction
  • Froude number
  • Hydraulic jump
  • turbulence model
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