بررسی آزمایشگاهی اثر زاویه اریب بر میدان جریان در کانال‌های‌ مرکب مورب با سیلاب‌دشت‌های مایل

نوع مقاله : مقاله کامل پژوهشی

نویسندگان

گروه عمران، دانشکده مهندسی، دانشگاه بوعلی سینا، همدان

چکیده

در طبیعت به ­علت تأثیر شرایط توپوگرافی محلی، رودخانه‌ها اغلب دارای شکل نامنظم و غیر منشوری هستند. در کانال‌های مرکب غیرمنشوری به­ دلیل تأثیر تغییر شکل مقطع در طول کانال، ساختار جریان پیچیده‌تر از کانال‌های مرکب منشوری است. به­ همین دلیل بررسی ویژگی‌های جریان در چنین کانال‌‌‌‌هایی امری مهم بوده و می‌تواند به محققان در درک بهتر رفتار جریان در رودخانه‌ها به‌ویژه در مواقع سیلابی کمک کند. در پژوهش حاضر رفتار جریان در کانال مرکب با سیلاب‌دشت‌های موربِ مایل به‌صورت تجربی بررسی شده است. آزمایش‌ها در سه عمق نسبی 2/0، 3/0 و 4/0 و برای دو زاویه اریب 31/11 و 81/3 درجه انجام شده است. نیمرخ طولی سطح آب، توزیع عرضی سرعت جریان و تنش برشی مرزی در طول ناحیه اریب اندازه‌گیری و گزارش شده است. نتایج حاصله بیانگر آن است که توزیع عرضی سرعت و تنش برشی مرزی در کانال‌های مرکب مورب با سیلاب‌دشت‌های مایل به‌صورت نامتقارن و غیریکنواخت است. همچنین سرعت جریان و تنش برشی مرزی در سیلاب‌دشت‌ واگرا همواره بیشتر از مقدار نظیر آن در سیلاب‌دشت همگرا است. با افزایش زاویه اریب سیلاب‌دشت‌ها از81/3 به 31/11 درجه، تنش برشی مرزی و سرعت جریان در  سیلاب‌دشت‌ها و کانال اصلی افزایش می‌یابند لیکن نوسانات سطح آب کمتر می‌شود.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Experimental Study of the Effects of Skew Angle on Flow Field in Skewed Compound Channels with Inclined Floodplains

نویسندگان [English]

  • Mostafa Dolati Mahtaj
  • Bahram Rezaei
Civil Engineering Department, Faculty of Engineering, Bu-Ali Sina Univercity, Hamedan, Iran
چکیده [English]

During a flood, water flows out of the main channel and enters the floodplains. In nature, due to the influence of local topographic conditions, rivers have often irregular and non-prismatic shape. In non-prismatic compound channels, because of the effect of changing in cross-sectional area along the channel, the flow structure is more complex than prismatic compound channels. Therefore, it is important to study the flow characteristics in such channels and it can help researcher to better understand the flow behavior in rivers, especially during floods. In the present study, the flow characteristics in a compound channel with inclined and skew floodplains has been investigated experimentally. The experiments were performed at three relative depths of 0.2, 0.3 and 0.4 and for two skew angles of 11.31° and 3.81°. The water surface profile, lateral distributions of velocity and boundary shear stress along the skew part of the flume have been measured and reported. The results of experiments indicate that the lateral distributions of velocity and boundary shear stress in skewed compound channels with inclined floodplains are non-uniform and asymmetric. Also, the flow velocity and boundary shear stress in diverging floodplain are always higher than its value in converging floodplain. By increasing the skew angle of the floodplains from 3.81 to 11.31 degrees, the boundary shear stress and flow velocity in the main channel and on the floodplains increase.

کلیدواژه‌ها [English]

  • Non-prismatic compound channel
  • Skewed floodplains
  • Inclined floodplains
  • Velocity distribution
  • Boundary shear stress
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