بررسی آزمایشگاهی عملکرد صفحات مثلثی بر توپوگرافی بستر در رودخانه‌های مستقیم

نوع مقاله: مقاله پژوهشی

چکیده

آبشکن­ها از جمله سازه­هایی هستند که برای حفاظت سواحل و ساماندهی رودخانه­ها بکار می­روند. آنها معمولاً به شکل دیواره مستطیلی و عمود بر جریان می­باشند. توسعه آبشستگی در دماغه آنها متاسفانه عامل تخریب سازه است. علاوه بر این محدوده رسوبگذار بین آبشکن‌ها و نیز افزایش سرعت جریان در میانه مجرا، بدلیل انسداد زیاد، از جمله عواملی هستند که مشکلاتی را برای زندگی آبزیان رودخانه فراهم می‌کند. صفحات مثلثی از جمله سازه­هایی است که مشکلات مربوط به آبشکن­های مستطیلی در آنها حداقل می­باشد. بررسی عملکرد صفحات مثلثی بر تغییرات توپوگرافی بستر در شرایط مختلف جریان هدف اصلی این مقاله است. برای این منظور آزمایش­هائی در یک فلوم مستقیم برای شرایط مختلف جریان (پنج عدد فرود 18/0، 2/0، 22/0، 24/0 و 26/0) با نصب صفحات مثلثی به ازای زاویه 30 درجه و فاصله 4 برابر طول موثر سازه انجام گردید. در انتهای هر آزمایش توپوگرافی بستر توسط متر لیزری برداشت گردید. نتایج نشان داد که، ابعاد هندسی چاله آبشستگی در آبشکن­های مستطیلی بزرگتر از صفحات مثلثی می‌باشد بگونه­ای که بطور متوسط طول و عمق چاله آبشستگی در آبشکن­های مستطیلی به ترتیب 3/1 و 5/1 برابر در صفحات مثلثی است. در ضمن فاصله بیشینه عمق آبشستگی از ساحل در صفحات مثلثی حدود 40% بیشتر از آبشکن­های مستطیلی است که این یک مزیت برای صفحات مثلثی محسوب می­شود.

کلیدواژه‌ها


عنوان مقاله [English]

Experimental Investigation of the Performance of Triangular Vanes on Bed Topography in Straight Rivers.

چکیده [English]

             Spur dikes are one of the structures used for protection of river banks from erosion and rivers organization. They are usually rectangular and perpendicular to the flow. Unfortunately, the scour development in the tip of those can lead damage to the structure. Furthermore, sedimentation between the spur dikes as well as increasing the flow velocity in the middle of the channel due to the large obstruction, are among the factors that create problems for aquatic life of the river. These problems are minimal in the triangular vanes. The main purpose of this paper is to evaluate the performance of the triangular vanes on bed topography changes in the different flow conditions. For this reason, some tests were carried out at a straight flume for different flow conditions (five Froude numbers of 0.18, 0.20, 0.22, 0.24 and 0.26) by installing series of triangular vanes with space of 4Le (Le is the effective length of structure) at the angle of 30 degrees to the upstream bank. At the end of each test the bed topography was measured by laser distance measurer. The results showed that, the geometric dimension of the scour hole for the rectangular spur dikes was larger than that for the triangular vanes. On average, the length and depth of scour hole for the rectangular spur dikes were 1.3 and 1.5 times higher in comparison to those for triangular vanes, respectively. In addition, the position of the maximum scour depth for the triangular vanes was about 40% farther from the bank than that case of rectangular spur dikes that was an advantage for the triangular vanes.

کلیدواژه‌ها [English]

  • River banks
  • Scour
  • Spur dike
  • Triangular vanes
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