تأثیر شکل کانال در تخلیه سطحی جریان چگال از دو مقطع مستطیلی و ذوزنقه‌ای در محیط‌های ساکن و همگن

نوع مقاله: مقاله پژوهشی

نویسندگان

1 دانشجوی کارشناسی ارشد مهندسی آب، دانشگاه تربیت مدرس، تهران، ایران

2 استادیار گروه عمران، دانشگاه صنعتی نوشیروان بابل

3 استاد گروه سازه‌های آبی، دانشگاه تربیت مدرس، تهران

4 استاد گروه آب و محیط زیست، دانشکده عمران، دانشگاه علم و صنعت ایران، تهران، ایران

چکیده

در سال‌های اخیر با افزایش جمعیت و صنعتی شدن جهان، صنایع نمک‌زدایی از آب دریا به‌منظور تأمین نیازهای فزاینده شهرهای ساحلی به آب شیرین، گسترش زیادی یافته‌اند. پساب بسیار شور، محصول ثانویه فرایند تولید آب شیرین در تأسیسات نمک‌زدایی آب دریا است که معمولاً با استفاده از انواع تخلیه‌کننده‌های دریایی سطحی و مستغرق به محیط دریا تخلیه می‌شود. هدف اصلی تخلیه‌کننده‌ها دستیابی به ترقیق مناسب و کاهش اثرات مخرب محیط‌‌زیستی تخلیه فاضلاب بر محیط زیست است. در این پژوهش اثر شکل کانال در تخلیه‌ سطحی پساب‌های با شناوری منفی از دو مقطع مستطیلی و ذوزنقه‌ای با قطر معادل یکسان در محیط ساکن و همگن مورد بررسی قرار گرفت. آزمایش‌ها در اتاق تاریک و با استفاده از دوربین دیجیتال انجام شد و از طریق تحلیل رقومی تصاویر، مورد پردازش قرار گرفت. موقعیت نقطه غوطه‌وری، نقطه برخورد و میزان ترقیق در نقطه برخورد همراه با موقعیت و ترقیق نهایی جریان در محیط از جمله پارامترهای مورد بررسی در این پژوهش بود. نتایج مشاهدات آزمایشگاهی به‌صورت کمّی در قالب مجموعه‌ای از نمودارها و روابط بی‌بعد ارائه شد. در نهایت از سنجه‌های آماری مانند مقادیر ریشه میانگین مربعات خطا (RMSE) و ضریب تعیین (R2) برای بررسی دقت روابط بی‌بعد ارائه شده، استفاده شد. نتایج به‌دست آمده بیانگر آن است که هرچه شکل کانال تخلیه‌کننده به شکل بهترین مقطع هیدرولیکی (نیم دایره) نزدیک‌تر باشد، جریان در امتداد ناحیه میدان نزدیک، مشخصات هندسی و اختلاط بهتری خواهد داشت.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

The Impact of Channel Shape at Surface Discharge from Rectangular and Trapezoid Sections into Stagnant and Non-stratified Water Bodies

نویسندگان [English]

  • Fatemeh Shacheri 1
  • Ozeair Abessi 2
  • Jamal Mohammad Vali Samani 3
  • Mohsen Saeedi 4
1 MSc Student of Water Structure Engineeing, Tarbiat Modares University, Tehran, Iran
2 Assist. Prof., School of Civil Engineering, Nooshiravani University of Technology, Babol, Iran
3 Prof. of Water Structure Engineering, Tarbiat Modares University, Tehran
4 Prof. of Water and Environment, School of Civil Engineering, Iran Unversity of Science and Technology, Tehran, Iran
چکیده [English]

In recent years, with growing population and industrialization of the world, desalination techniques have developed drastically to supply the rising needs of coastal cities to fresh water. The brine is the second product of the producing fresh water process in the desalination facilities, that is usually discharged into the sea through marine outfalls (surface and submerged). The main purpose of the outfall is to enhance the dilution and reduce the impact on the local environment. In this study, in order to investigate the impact of the shape of the surface discharge channel, rectangular and trapezoidal sections with the equivalent diameter were used to discharge wastewater with negative buoyancy into stagnant and non-stratified water bodies. Experiments have been carried out in a dark room and processed using digital analysis. The location of plunge point, impact point and the dilution in this point, and the location of the ultimate point and dilution at this point were the flow characteristics studied in this research. According to the shape impact and less hydraulic conflict with the surroundings, trapezoidal section had better geometric characteristics compared to rectangular section. Results of the experiments were presented in the form of non-dimensional diagrams and equations. Finally, statistical indices such as Root Mean Square Error (RMSE) and R-Square (R2) were used to verify the accuracy of the presented dimensionless equations. The results indicated that the closer the shape of surface channel discharge is to the best hydraulic cross section (semicircular), the better geometric and mixing characteristics would be obtained for the flow along near-field area. In this way, prediction of flow characteristics and design of actual samples of these outfalls will be possible.

کلیدواژه‌ها [English]

  • Shape Impact
  • Dense Flow
  • Surface Discharge
  • Mixing
  • Densimetric Froude Number

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