بررسی عددی اثرات زاویه واگرایی بستر سیلابی غیر منشوری بر سرعت جریان در مقطع عرضی کانال‌های مرکب

نوع مقاله : مقاله پژوهشی

نویسندگان

1 استادیار گروه‌ مهندسی ‌عمران، دانشکده ‌‌مهندسی ‌کبودرآهنگ، دانشگاه بوعلی سینا، همدان، ایران

2 دانشجوی کارشناسی ارشد، دانشکده مهندسی، دانشگاه بوعلی سینا، همدان، ایران

10.22034/jewe.2021.250562.1434

چکیده

غیرمنشوری بودن کانال اصلی و سیلاب‌دشت‌ها در کانال مرکب و اندرکنش شدید جریان کم‌سرعت سیلاب‌دشت‌ها در عبور از روی جریان پرسرعت کانال اصلی، موجب شکل‌گیری جریان‌های ثانویه می‌شود. تاکنون مطالعات جامعی در مورد تغییر زاویه واگرایی سیلاب‌دشت‌ها به‌صورت مدل عددی و فیزیکی صورت نگرفته و به علت تأثیرگذار بودن این پارامتر، ضرورت بررسی آن مشخص می‌گردد. در پژوهش حاضر سعی شده با استفاده از مدل سه‌بعدی Ansys-Fluent، هیدرولیک جریان در مقاطع مرکب با سیلاب‌دشت‌های واگرا به ازای پنج زاویه واگرایی 3، 6، 9، 12 و °15 و در سه مقطع 2، 8 و m 14 با مدل آشفتگیk-ε  استاندارد و روش (VOF) شبیه‌سازی شود. شرایط مرزی استفاده‌شده در این پژوهش، مرز ورودی نرخ جرمی جریان، مرز خروجی به‌صورت خروجی فشار، مرزهای جامد به‌صورت دیوار بدون لغزش و بدون زبریو مرز بالایی کانال به‌صورت دیوار بدون لغزش و بدون زبری بود. نتایج بررسی دقّت پیش­بینی سرعت میانگین عمقی در مقطع m 14 کانال نشان داد که در کلیه مقاطع کانال، نتایج مدل‌سازی­ها در محدوده مجاز خطای تعریف‌شده برای مدل­های عددی قرار دارند که نشان‌دهنده تطابق مناسب نتایج آزمایشگاهی و شبیه‌سازی می‌باشد. نتایج نشان داد که بیش‌ترین سرعت در کانال با زاویه واگرایی °3 اتفاق می‌افتد و هر چه زاویه واگرایی بیش‌تر شود، سرعت کم‌تر می‌شود. همچنین حداکثر تنش برشی در کانال با زاویه واگرایی سه درجه و کم‌ترین تنش برشی در زاویه واگرایی °15 می‌باشد. عمق آب با زاویه واگرایی کم‌تر، بیش‌تر است و هر چه زاویه واگرایی بیش‌تر می‌شود عمق آب کم‌تر می‌شود.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Numerical Study of the Effects of Non-Prismatic Floodplain Divergence Angle on Flow Velocity in the Cross Section of Compound Channels

نویسندگان [English]

  • Morteza Shokri 1
  • Reza Mehdipour 2
1 Assist. Professor, Department of Civil Engineering, Kabodarahang Engineering Faculty, Bu-Ali Sina University, Hamedan, Iran
2 M.E. Student, Department of Civil Engineering, Faculty of Engineering, Bu Ali Sina University, Hamadan, Iran
چکیده [English]

The formation of the secondary flows is caused by the non-prismatic nature of the main channel and floodplains in the compound channel and the intense interaction of the low-velocity flow of the floodplains in passing over the high-velocity flow of the main channel. So far, comprehensive studies on changing the divergence angle of floodplains have not been done as a numerical and physical model, and due to the effectiveness of this parameter, its study is necessary. In the present study, using the three-dimensional Ansys-Fluent model, simulation was performed based on the standard k-ε turbulence model and VOF method for the hydraulic flow in compound channel with divergent floods for five divergence angles of 3, 6, 9, 12 and 15° and in three sections of 2, 8 and 14 m. The boundary conditions used in this research were the input limit of the mass flow rate, the output boundary as a pressure outlet, the solid boundaries as a non-slip wall without roughness and the upper boundary of the channel as a non-slip wall without roughness. The results of accurately predicting the average depth velocity in the section Z = 14 m of the channel showed that in all sections of the channel, the modeling results were within the allowable error range defined for numerical models, indicating the appropriate matching of laboratory and simulation results. The results showed that the maximum velocity in the channel occurs with a divergence angle of 3° and the higher the divergence angle, the lower the velocity. Moreover, the maximum shear stress in the channel is with a divergence angle of 3° and the minimum shear stress is in the divergence angle is 15°. The lower the water angle, the higher the divergence angle, and the higher the divergence angle, the lower the water height.

کلیدواژه‌ها [English]

  • Ansys Fluent
  • divergence angle
  • Divergent Floodplain
  • Non-prismatic Channel
  • VOF
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