تخمین سرعت متوسط عمقی و تنش برشی در کانال مثلثی باز

نوع مقاله: مقاله پژوهشی

نویسندگان

1 دانشیار گروه مهندسی عمران، دانشگاه فردوسی مشهد

2 استادیار گروه مهندسی عمران، دانشگاه سیستان و بلوچستان

چکیده

روش ارائه شده توسط شیونو و نایت (SKM) قادر به تخمین توزیع سرعت متوسط عمقی و تنش برشی در کانال‌های باز است. SKM نیاز به کالیبره شدن دارد. پارامترهایی که باید کالیبره گردند عبارت‌اند از فاکتور اصطکاک f، لزجت چرخشی عرضی λ و جریان ثانویه Γ. از بین این پارامترها،λ =0.07  به‌عنوان مقدار استاندارد لزجت چرخشی در مسائل کاربردی درنظر گرفته می‌شود. بنابراین، دقت تخمین توزیع سرعت متوسط عـمقی و تنــش برشی با SKM به نحوه تعیینf  وΓ مرتبط خواهد بود. دراین مقاله، الگوهای سلول‌های جریان ثانویه (Γ) و توزیع فاکتور اصطکاک (f) در یک کانال مستقیم منشوری مثلثی با زبری یکنواخت ارائه شد. در تعیین بهترین ساختار توزیع فاکتور اصطکاک از روش سعی و خطا استفاده گردید تا با استفاده از SKM بهترین نتایج حاصل گردد. نتایج به‌دست آمده از مقایسه توزیع سرعت متوسط عمقی و تنش برشی تخمین زده شده توسط SKM و اطلاعات آزمایشگاهی نشان می‌‌داد که اگر دو پارامتر f  وΓ  براساس الگوهای صحیحی انتخاب شوند، SKM می‌تواند توزیع سرعت و تنش برشی را به‌درستی تخمین بزند.

کلیدواژه‌ها


عنوان مقاله [English]

Estimation of Depth-Averaged Velocity and Boundary Shear Stress in a Triangular Open Channel

نویسندگان [English]

  • Mahmoud Faghfour Maghrebi 1
  • Mohammad Givehchi 2
1 Assoc. Prof., Dept. of Civil Eng., Ferdowsi University, Mashhad
2 Assist. Prof., Dept. of Civil Eng., Sistan and Baluchestan University
چکیده [English]

The proposed method by Shiono and Knight (SKM) is able to predict the lateral depth-averaged velocity and shear stress distribution in open channels. The SKM is needed to be calibrated. The calibration parameters are friction factor f, lateral eddy viscosity λ, and secondary flow Γ. In practical problems, the assumption of λ =0.07 from among these is considered as a standard value for the eddey viscosity. Thus, the accuracy of the depth-avergad and the shear stress distributions using SKM will be subject to the determination of f and Γ. In the present paper, we present the secondary flow cell pattern (Γ) and friction factor distribution (f) in a straight prismatic triangular channel with a uniform roughness. The trial and error approach is used to define the best pattern of friction factor to produce the most appropriate results. The results of predicted depth-averaged velocity as well as shear stress distributions obtained from SKM as compared to  measured values indicate that SKM can accurately predict the velocity and shear stress distributions if the two coefficients of f and Γ are chosen based on accurate patterns.

کلیدواژه‌ها [English]

  • Depth-averaged velocity
  • friction factor
  • Secondary Flow Cell
  • Triangular Channel
  • Shear Stress
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