بررسی آزمایشگاهی نوسانات فشار پرش هیدرولیکی در حوضچه آرامش با واگرایی ناگهانی و بستر زبر

نوع مقاله : مقاله پژوهشی

نویسندگان

1 دانشجوی دکتری، گروه عمران، واحد چالوس، دانشگاه آزاد اسلامی، چالوس، ایران

2 استادیار، گروه عمران، واحد چالوس، دانشگاه آزاد اسلامی، چالوس، ایران

چکیده

اثر فشارهای نوسانی ناشی از تلاطم در پرش هیدرولیکی موجب آسیب قابل‌توجهی در حوضچه آرامش می­شود. هم­چنین، وجود زبری در بستر باعث تغییر دادن رفتار خطوط جریان و تشکیل گردابه ­ها در طول پرش می‌شود. از این­‌رو، هدف پژوهش حاضر تعیین اثر حضور زبری بر فشارهای هیدرودینامیکی در پرش هیدرولیکی نوع S در مقاطع واگرای ناگهانی بود. برای این منظور آزمایش ­ها در یک کانال نسبتاً بزرگ به عرض 8/0 و طول m 12 در حوضچه آرامش با نسبت­های واگرایی 33/0، 5/0، 67/0 و 1 در محدوده اعداد فرود بین 2 تا 5/9 انجام شد. المان­های زبری با ارتفاع cm 3 و فواصل مشخص در بستر کانال و در پایین ­دست مقطع واگرایی جای­گذاری شد. به­‌منظور تعیین اثرات زبری در میزان فشارهای هیدرودینامیکی، آزمایش­ها در دو مرحله مجزا شامل بستر حوضچه کاملاً صاف و بدون حضور زبری در مرحله اول (77 آزمایش) و با حضور زبری در کف حوضچه در مرحله دوم (81 آزمایش) صورت پذیرفت. نتایج نشان داد که وجود زبری در بستر باعث کاهش شدت نوسانات فشار در حوضچه آرامش می‌شود. همچنین در مقاطع واگرای ناگهانی به­دلیل تشکیل گردابه­ های جانبی افت انرژی افزایش و شدت نوسانات فشار کاهش می ­یابد. آهنگ کاهش بیشینه نوسانات فشار به ­ترتیب 27، 46 و 58% برای نسبت واگرایی 67/0، 5/0 و 33/0 در بستر زبر تخمین زده شد.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Experimental Determination of Pressure Fluctuations in Stilling Basin with Sudden Expanding and Roughened Bed

نویسندگان [English]

  • Marzieh Naemhasani 1
  • Kouros Nekoufar 2
  • Morteza Biglarian 2
  • Morteza Jamshidi 2
1 PhD Scholar, Department of Civil Engineering, Chalous Branch, Islamic Azad University, Chalous, Iran
2 Assist. Professor, Department of Civil Engineering, Chalous Branch, Islamic Azad University, Chalous, Iran
چکیده [English]

The effect of fluctuating pressures due to turbulence on the hydraulic jump causes significant damage to the relaxation pool. Moreover, the presence of roughness in the bed changes the behavior of flow lines and the formation of vortices during the jump. Therefore, the aim of this study was to determine the effect of the presence of roughness on hydrodynamic pressures in type S hydraulic jump in sudden divergence sections. For this purpose, experiments were performed in a relatively large channel with a width of 0.8 and a length of 12 m in the calm pool with divergence ratios of 0.33, 0.5, 0.67 and 1 in the range of Frued numbers between 2 to 9.5. Roughness elements with a height of 3 cm and specified distances were placed in the channel bed and downstream of the divergence section. In order to determine the effects of roughness on the level of hydrodynamic pressures, the experiments were performed in two separate stages, including a completely flat pool bed without the presence of roughness in the first stage (77 experiments) and with the presence of roughness in the pool floor in the second stage (81 experiments). The results showed that the presence of roughness in the bed reduces the intensity of pressure fluctuations in the relaxation pool. In addition, in sudden divergent sections, due to the formation of lateral vortices, the energy drop increases and the intensity of pressure fluctuations decreases. The maximum reduction rates of pressure fluctuations were estimated to be 27, 46 and 58% for the divergence ratios of 0.67, 0.5 and 0.33 in the rough bed, respectively.

کلیدواژه‌ها [English]

  • Abrupt Expanding
  • Hydraulic jump
  • Pressure Fluctuations
  • Rough Stilling Basin
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