تحلیل تنش برشی در کانال های نیم سهموی

نوع مقاله: مقاله پژوهشی

نویسندگان

1 گروه سازه های آبی دانشکده مهندسی علوم آب دانشگاه شهید چمران اهواز، ایران

2 استاد گروه سازه های آبی، دانشکده مهندسی علوم آب، دانشگاه شهید چمران اهواز

چکیده

پیش­بینی دقیق توزیع تنش برشی مرزی در کانالهای روباز در بسیاری از مسائل مهندسی نظیر طراحی کانال­های پایدار، محاسبات مربوط به افت انرژی و رسوب­گذاری در کانال­ها حائز اهمیت می­باشد. مطالعه­های حاضر به بررسی چگونگی توزیع تنش­برشی در کانال­های نیم سهموی به دو روش انرژی و مومنتم و تغییرات آن در شرایط مختلف هیدرولیکی پرداخته است. برای تعیین تغییرات تنش­برشی موضعی به روش انرژی از لوله پرستون با قطر خارجی چهار میلی­متر مجهز به سلول­های حساس به فشار دینامیک استفاده گردید. برای تبدیل فشار قرائت شده به تنش­برشی از منحنی کالیبراسیون پتل استفاده شد. برای اندازه­گیری مستقیم تنش­برشی کل به روش مومنتم از روش فلوم لبه چاقویی استفاده شد. در نهایت روابطی برای تخمین تنش­برشی در جدارهای صاف و زبر در کانال­های نیم سهموی ارائه گردید. نتایج نشان دهنده این موضوع می­باشد که تنش­برشی جداره کانال در شرایط بستر صاف و زبر به­ترتیب به­طور متوسط 7/3 درصد و 6/4 درصد بیش از تنش بستر می­باشد. هم­چنین اندازه­گیری تنش­برشی جداره و بستر به روش مومنتم در شرایط جداره صاف و زبر به­طور متوسط مقادیر  تنش برشی را 7/2 درصد و 85/5 درصد بیش از روش انرژی نشان می­دهد.

کلیدواژه‌ها


عنوان مقاله [English]

Boundary Shear Stress Analysis in Semi-Parabolic Channels

نویسندگان [English]

  • Siavash Heydari orojlo 1
  • Manochehr Fathi Moghadam 2
1 Faculty of water Sciences Engineering, Shahid chamran University
2 Associated Professor, Faculty of Water Sciences Engineering, Shahid Chamran University of Ahvaz, Iran
چکیده [English]

Due to problems with on-site irrigation channels, such as occupying a high level of the land, a lack of suitable loan materials, and the possibility of dealing with multiple complications, the use of prefabricated channels is one of the most competitive options available for the  existing channels. From the theoretical point of view, the most effective hydraulic cross-section for the coated channels in which smooth water flows is the semicircular section. Nevertheless, in terms of implementation, the use of the semicircular cross-section is generally limited to the reinforced concrete channel. One of the important issues in outdoor hydraulic engineering is having sufficient knowledge about the amount of hydraulic resistance against the flow. The estimation of hydraulic resistance of the flow in open channels has always faced a serious challenge because of the presence of secondary currents and the vortex viscosity. The determination of the contribution of flow pipes in the bed and wall is faced with errors due to the effects of the walls on the maximum velocity position. Accurate prediction of boundary shear stress distributions in the open-channel flow is crucial in many engineering problems, such as channel design, the balance of energy, and sedimentation. Determining the exact bed and wall shear stress is important from a theoretic and applied point of view, for example, its role in scour and sedimentation studies and designing shield conservations.

کلیدواژه‌ها [English]

  • Shear Stress
  • Semi-parabolic Channel
  • Preston Tube
  • Momentum Method

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