تاثیر ابعاد و اندازه ذرات آبگیر بر ضریب دبی آبگیرهای کفی متخلخل با استفاده از مدل فیزیکی

نوع مقاله : مقاله پژوهشی

نویسندگان

1 دانش‌آموخته دکتری گروه علوم و مهندسی آب، دانشگاه فردوسی مشهد.

2 استاد گروه علوم و مهندسی آب، دانشگاه فردوسی مشهد

3 دانشیار گروه علوم و مهندسی آب، دانشگاه فردوسی مشهد.

چکیده

در رودخانه­های کوهستانی یکی از مناسب­ترین روش­های آبگیری استفاده از آبگیرهای کفی می­باشد. آبگیرهای کفی با محیط متخلخل یکی از اشکال مختلف آبگیرهای کفی بوده که تا کنون کمتر مورد مطالعه قرارگرفته­اند. در تحقیقات پیشین نحوه ساخت مدل­های آزمایشگاهی با آنچه در شرایط طبیعی وجود دارد تفاوت اساسی داشته، لذا در این پژوهش تلاش شده کاستی روش­های قبلی برطرف شود. در مقاله حاضر به منظور بررسی تاثیر ابعاد آبگیر بر ضریب دبی جریان انحرافی مدل­های مختلفی از آبگیر با سه طول ( cm45,30,15=L) و سه ارتفاع ( cm20,15,10=H) در کانال آزمایشگاهی تعبیه و فضای داخل آبگیر نیز توسط چهار نوع سنگدانه با دانه­بندی مختلف (mm75/17، 4/15، 4/13، 72/9 =d50) پر گردید. در هر سری از آزمایش­ها (مجموعاً 180 آزمایش) با عبور دبی­های متفاوت از روی آبگیر دبی انحرافی توسط آبگیر کفی متخلخل اندازه­گیری شد. مقایسه نتایج بدست آمده از این تحقیق با تحقیقات پیشین نشان از کاهش 10 درصدی در میزان دبی انحرافی توسط آبگیر را داشت. در نهایت با استفاده از تحلیل ابعادی و رگرسیون چند متغیره معادله­ای با ضریب همبستگی 85/0= 2R جهت برآورد ضریب دبی جریان انحرافی این نوع آبگیر، تحت تاثیر پارامترهای مختلف ارائه گردید.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Effect of Intake Particle Dimension and Grain Size on Discharge Coefficient in Porous Bottom Intakes Using Physical Modeling

نویسندگان [English]

  • Hossain Shariaty 1
  • Saeed Reza Khoda Shenas 2
  • Kazem Esmaili 3
1 Ph.D. Graduate, Dept. of Water Engineering, Ferdowsi University of Mashhad.
2 Professor, Dept. of Water Engineering, Ferdowsi University of Mashhad
3 Associate Professor., Department of Water Engineering, Ferdowsi University of Mashhad.
چکیده [English]

Water intake from the river is done using several methods. Each method has its own features and limitations. In steep mountain rivers with irregular bed, high values of sediment transport and flash floods may prevent the application of gated dams; therefore, the bottom intakes are often used. In this method, in some part of the river width and length, a trench is created with a proper cross section and water is flowed through this trench into the diversion channel. In order to prevent  the coarse particles to enter, top of the trench is covered with bottom rack bars. Corrosion of the bars, clogging, and maintenance are the common problems of bottom racks, which make them unusable in long term. To solve these problems, a new system of bottom intake with porous media is introduced. In this method, after trenching in the river bed, materials with appropriate aggregation are ‎dumped in the trench and water intakes from the river through a diversion channel. ‎ This means that  a portion of flow into the porous media; then move to the diversion channel. Another portion of the water passes over the bottom intake and finally drive to the river. Usage of the porous media has, however, many limitations; but it has some advantages, such as, no suspended solids in the water, respect for the environmental problems, no change in natural morphology of the river, withstanding in different weather conditions, and dealing with the problem of freezing, and corrosion, easy to construct and applicability, affordability and availability of materials. Despite a long history of research in thre field of bottom rack intakes, few studies about these structures with porous media have been previously done. In previous experiments, in order to separate the diverted flow from the non-passed flow, a bottom intake with porous media with a diversion channel parallel to the main channel was used, so that the diverted flow was unidirectional to the main channel. But, in practice, diversion channel in the bottom intakes is usually performed perpendicular to the main channel. Therefore, it affects the hydraulic parameters and diverted discharge. Besides, in previous experiments, by considering the constant height and length, the effect of these two factors has not been investigated for the intake. Therefore, in the present study, in order to precisely investigate   the hydraulic behavior of the bottom rack intakes, in addition to the implementation of a channel perpendicular to the main channel as a diversion channel, various factors such as the length and height of the intake, the effects of uniformity of particles and different slopes of intake have been experimentally investigated. The results of experiments on laboratory models in this study may reveal some of the unknown points in application of this method and it provides the possibility of design and operation of this structure in the natural environment.

کلیدواژه‌ها [English]

  • Bottom intake
  • Mountainous River
  • Porous media
  • spatially varied flow
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