اثر شیب منفی، زبری بستر و پله انتهایی بر پروفیل سرعت و نوسانات فشار پرش هیدرولیکی

نوع مقاله: مقاله پژوهشی

نویسندگان

1 دکتری آبیاری و زهکشی، دانشگاه صنعتی اصفهان

2 استاد گروه مهندسی آب، دانشکده کشاورزی، دانشگاه صنعتی اصفهان.

3 استادیار گروه مهندسی آب، دانشکده کشاورزی، دانشگاه شیراز.

چکیده

حوضچه­های آرامش برای کنترل پرش هیدرولیکی تحت شرایط شیب معکوس و زبری بستر مورد توجه پژوهشگران قرار گرفته است. در این پژوهش اثر هم­زمان سه شیب منفی، سه قطر زبری و دو ارتفاع پله مثبت انتهایی بر پروفیل سرعت و نوسانات فشار در اعداد فرود 4 تا 10 بررسی شده است. بر­اساس نتایج ضخامت لایه مرزی بی­بعد71/0محاسبه شد که در مقایسهبا بستر صاف قابل ملاحظه بود. هم­چنین تنش برشی6/12برابر شرایطبسترصاف به­دست آمد. نتایج نشان داد سه عامل شیب منفی، زبری بستر و پله مثبت انتهایی باعث کاهش انحراف معیار استاندارد نوسانات فشار نسبت به حالت کلاسیک می­شود. بیشترین مقدار ضریب بدون بعد انحراف معیار استاندارد نوسانات فشار و ضریب بدون بعد نوسانات فشار به­ترتیب برابر 027/0 و 275/0 محاسبه شد که در مقایسه با حالت کلاسیک به­ترتیب 6/65 و 7/64 درصد کاهش داشته است. هم­چنین حداقل ضریب کاویتاسیون در این مطالعه برابر 87/3 محاسبه گردید و بنابراینسازهبامشکل کاویتاسیونمواجهنخواهد بود.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Effect of Negative Slope, Bed Roughness and Positive Step on Velocity Profile and Pressure Oscillations of Hydraulic Jump

نویسندگان [English]

  • Nahid Pourabdollah 1
  • Manouchehr Heidarpour 2
  • Jahangir Abedi-Koupai 2
  • Jahanshir Mohamadzadeh Habili 3
1 PhD Student, Water Engineering Department, Isfahan University of Technology, Iran
2 Professor, Water Engineering Department, Isfahan University of Technology, Iran.
3 Assistant Professor, Water Engineering Department, Shiraz University, Iran.
چکیده [English]

The control of speed and pressure oscillations along the stream, as two critical parameters in designing hydraulic systems, is vital since they have to be set within an acceptable range in order to prevent damages to hydraulic structures. Ead and Rajaratnam (2002) studied the hydraulic jump characteristics on the corrugated bed and calculated the thickness of dimensionless boundary layer to be 0.45. Pourabdollah et al. (2015) investigated the effect of roughness and adverse slope of the bed on the velocity profile and determined the mean shear force coefficient to be 11.5 times more than that of the classical condition. Fiorotto and Rinaldo (1992) stated that in hydraulic jump the pressure is oscillating around the mean pressure value, which is almost equal to piezometric head at each point. Also Lopardo and Solari (1980) determined the pressure oscillations equal to 0.084 for hydraulic jump at downstream of valve. Accordingly, although various studies have been carried out on hydraulic jump characteristics under different conditions, the simultaneous effect of end positive step, bed roughness and adverse slope on hydraulic jump characteristics have not yet been explored. Therefore, the aim of this study was to investigate the velocity profiles, flow surface and pressure oscillations in hydraulic jump within the stilling basin at defined conditions.

کلیدواژه‌ها [English]

  • Boundary Layer Thickness
  • Standard Deviation
  • Shear Stress
  • Stilling basin
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