بررسی خصوصیات جریان و پارامترهای فشار پرش هیدرولیکی آزاد و مستغرق در حوضچه‌های آرامش USBR

نوع مقاله : مقاله پژوهشی

نویسندگان

1 کارشناس آزمایشگاه هیدرولیک، دانشکده کشاورزی دانشگاه تبریز

2 استاد گروه مهندسی آب، دانشگاه تبریز

3 دانشیار گروه مهندسی آب، دانشگاه تبریز

چکیده

در این تحقیق، خصوصیات جریان و پارامترهای فشار در پرش هیدرولیکی در یک فلوم آزمایشگاهی بررسی شده است. نتایج حاصل برای اعداد فرود اولیه مختلف (Fr1) در پایین‌دست سرریز اوجی در کف حوضچه آرامش نوع دو USBR با حوضچه‌های نوع یک USBR مقایسه شده است. ابعاد سرریز اوجی شکل و حوضچه آرامش، بر اساس معیارهای USBR طراحی شده‌اند. داده‌های فشار نقاط واقع در کف حوضچه با استفاده از مبدل‌های فشار با بسامد 20 هرتز ثبت شده‌اند. پارامترهای آزمایشگاهی شامل عمق و سرعت جریان در موقعیت‌های ابتدا و انتهای پرش آزاد (Y1، Y2، V1، و V2)، و پرش مستغرق (Y3، Yt، V3، و Vt) اندازه‌گیری شدند. در تحقیق حاضر، پارامترهای بی‌بعد راندمان استهلاک انرژی (εt)، ارتفاع نظیر فشار متوسط (Ψ*X)، انحراف معیار نوسانات فشار (Φ*X)، ضریب حداکثر نوسان فشارهای مثبت (CP+)، ضریب حداکثر نوسان فشارهای منفی (CP)، ضریب کل نوسانات فشار (CP) و ضریب چولگی (Ad) بررسی شدند. مقادیر پارامترهای فشار تابع Fr1، موقعیت نقطه (Γ*X) و درجه استغراق (S) هستند. نتایج نشان داد که با کاهش مقادیر Fr1، پارامتر εt کاهش می‌یابد. پارامتر Φ*Xmax در حوضچه نوع دو USBR در مقایسه با حوضچه‌های نوع یک در پرش آزاد، در حدود 30 درصد کاهش می‌یابد. کاهش مقادیر Φ*Xmax در پرش مستغرق با  S=1/4  در مقایسه با پرش آزاد، در حدود 29 درصد است. مقادیر ضرایب CP+max و  |CP|maxدر پرش مستغرق با   S=1/4در مقایسه با پرش آزاد، به طور متوسط به ترتیب برابر با 15 و 17 درصد کاهش می‌یابند.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Investigation of Flow Characteristics and Pressure Parameters of Free and Submerged Hydraulic Jumps in USBR Stilling Basins

نویسندگان [English]

  • Seyed Nasrollah Mousavi 1
  • Farsadizadeh Davood 2
  • Farzin Salmasi 3
  • Ali Hosseinzadeh Dalir 2
1 Hydraulic Lab Expert, Water engineering Department, Tabriz University, Iran
2 Prof., Dept. of Water Eng., Faculty of Agric., Univ. of Tabriz, Iran
3 Assoc. Prof., Dept. of Water Eng., Faculty of Agric., Univ. of Tabriz, Iran
چکیده [English]

In this study, flow characteristics and pressure parameters of hydraulic jumps have been investigated in a laboratory flume. The results for different incident Froude numbers (Fr1), at the downstream of an Ogee spillway on a typified USBR II stilling basin bed were compared with the USBR Type I basins. Dimensions of the Ogee spillway and stilling basin were designed according to the USBR criteria. The pressure data of the points on the basin bed were recorded using pressure transmitters with 20 Hz frequency. Experimental parameters, including flow depths and velocities at the beginning and endpoint of free jumps (Y1, Y2, V1 and V2), and submerged jumps (Y3, Yt, V3 and Vt) were measured. In the present study, dimensionless parameters of energy dissipation efficiency (εt), mean pressure head (Ψ*X), the standard deviation of pressure fluctuations (Φ*X), maximum positive pressure fluctuation coefficient (CP+), maximum negative pressure fluctuation coefficient (CP), total pressure fluctuation coefficient (CP) and skewness coefficient (Ad) were investigated. Pressure parameters are dependent on Fr1, the dimensionless position (Γ*X), and the submergence degree (S). The results showed that by reducing the Fr1 values, the εt parameter decreases. The Φ*Xmax value in the USBR Type II basin decreases around 30% compared to the Type I basins in free jumps. The reduction of Φ*Xmax values in the submerged jump with S=1.4 is about 29% than free jumps. The CP+max and |CP|max coefficients in the submerged jump with S=1.4 in comparison with free jumps decrease about 15 and 17%, respectively.

کلیدواژه‌ها [English]

  • Ogee spillway
  • pressure coefficients
  • standard deviation of pressure fluctuations
  • submergence degree
  • USBR stilling basin
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