آبشستگی آب زلال در اطراف سرریز جانبی کلیدپیانویی تیپ A در زاویه 120 درجه یک کانال قوسی 180 درجه

نوع مقاله : مقاله پژوهشی

نویسندگان

1 دانش آموخته، گروه مهندسی آب، دانشکدگان ابوریحان، دانشگاه تهران

2 گروه مهندسی آب، دانشکدگان ابوریحان، دانشگاه تهران

3 پژوهشکده حفاظت خاک و آبخیزداری، سازمان تحقیقات، آموزش و ترویج کشاورزی، تهران، ایران

چکیده

سرریز جانبی یک سازه کنترل هیدرولیکی است که در سیستم­های آبیاری و زهکشی و سیستم‌های فاضلاب ترکیبی استفاده می­شود. سرریزهای کلیدپیانویی نوع جدیدی از سرریزهای چند وجهی هستند که می­توانند با ایجاد طول بیشینه تاج سرریز در عرض محدود به عبور بهتر جریان کمک کنند. این سازه­ها دارای شکل جدیدی از تاج سرریز، با راندمان بالا سازه­های اقتصادی هستند. به دلیل مزیت­های این سرریز لزوم مطالعه و تحقیق روی آبشستگی اطراف این سرریزها بعنوان سرریز جانبی الزامی می باشد. مطالعه حاضر بر روی آبشستگی اطراف سرریز جانبی کلید پیانویی تیپ A در شرایط آب­زلال در یک کانال قوسی 180 درجه و در زاویه 120 درجه تمرکز دارد. نتایج حاکی از آن بود که در انتهای پایین­دست سرریز جانبی حفره­هایی بصورت متوالی در وسط کانال و چاله آبشستگی نزدیک به قوس بیرونی به دلیل تغییرات تنش برشی و سرعت تشکیل شد. عمق آبشستگی در شرایط آب­زلال ابتدا به سرعت افزایش می­یابد، سپس با گذشت 200 دقیقه  به صورت تقریبی به شرایط تعادل می­رسد و به شدت جریان وابسته است. عمق تعادل آبشستگی به پارامترهای بی­بعد شدت جریان، ارتفاع آب بر روی سرریزجانبی، ارتفاع تاج سرریز و طول سرریز جانبی وابسته است و بیشترین مقدار عمق آبشستگی زمانی که نسبت بی بعد شدت جریان نزدیک به یک است بدست می­آید. همچنین عمق تعادل آبشستگی در نسبت­ بی­بعد  L/rc=0.175 در مقایسه با L/rc=0.125 در شدت جریان­های متفاوت به ترتیب 12 تا 35 درصد، 10 تا 39 درصد و 18 تا 26 درصد افزایش یافته است.

کلیدواژه‌ها

موضوعات

عنوان مقاله [English]

Clear Water Scour around at a Piano Key Side Weir of the Type A at 120° Section of a 180° Curved Channel

نویسندگان [English]

  • Mehdi Jamshidi 1
  • Jaber Soltani 2
  • Mohammad Rostami 3
  • Mojtaba Saneie 3
1 Department of Water Engineering, College of Aburaihan, University of Tehran, Tehran, Iran
2 Department of Water Engineering, College of Aburaihan, University of Tehran, Tehran, Iran
3 Dept. of River Engineering, Soil Conservation and Watershed Management Research Institute, Iran
چکیده [English]

A side weir is a hydraulic control structure used in irrigation and drainage systems and combined sewer systems. The Piano Key Weir (PKW) is a new type of long crest weirs that have a relatively simple structure and high economic efficiency structures. Due to the advantages of this weirs, it is necessary to study and investigate the Scour around of these structures as a side-weir. The present study focuses on investigate the scouring around the piano key Side weirs of the Type A at a 30° Section of a 180° Alluvial curved channel for clear water conditions. The results showed that at the end of the Side weir, longitudinal bar in the middle of the main channel and a scour hole close to the outer bank are formed because of the changes in shear stress field. The depth of clear-water scour increases by time and approaches the equilibrium state asymptotically depending on approach flow velocity. The equilibrium depth of scour depends on the dimensionless parameters of flow intensity, flow shallowness, weir crest height, side weir length and the maximum value of scour depth occurs at a depth when the approach flow intensity is equal to 1.0. Also, the scour equilibrium depth in the dimensionless ratio increased L/rc = 0.175 compared to L/rc = 0.125 in different flow velocity of 12 to 35%, 10 to 39% and 18 to 26%, respectively.

کلیدواژه‌ها [English]

  • Scour
  • Side Weir
  • Piano Key Side Weir
  • clear water
  • Curved Channel

مراجع

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