بررسی تأثیر ابعاد و موقعیت صفحات مستغرق افقی در کاهش حد استغراق بحرانی آبگیرهای قائم

نویسندگان

چکیده

یکی از روش‌های تأمین نیاز آبی بخش کشاورزی،‏ آب شهری و صنعتی،‏ برداشت آب از مخازن یا کانال‌های انتقال آب به‌وسیله آبگیرهای قائم است. این روش بیشتر با پدیده تشکیل جریان‌های گردابی در دهانه آبگیر مواجه است. این امر باعث ورود هوا و ایجاد جریان‌های پیچشی در داخل مجرای انتقال می‌شود که به‌دنبال آن مشکلات دیگری مانند کاهش ظرفیت آبگیری،‏ افزایش احتمال وقوع پدیده خلأزایی،‏ لرزش و سر و صدا به وقوع می‌پیوندد. در این پژوهش به بررسی تأثیر ابعاد و موقعیت صفحات مستغرق افقی در کاهش عمق استغراق مورد نیاز برای جلوگیری از تشکیل گرداب با هسته هوا پرداخته شد. ابتدا آزمایش‌هایی برای تعیین منحنی دبی- استغراق بحرانی آبگیر،‏ بدون نصب صفحات ضدگرداب انجام شد و یک معادله بی‌بعد بر حسب استغراق نسبی و عدد فرود ارائه شد. سپس تأثیر هر صفحه با ابعاد و موقعیت نصب مشخص به ازای پنج دبی مختلف بررسی شد. عملکرد صفحات در کاهش استغراق بحرانی مورد نیاز نسبت به حالت بدون صفحه یا شاهد،‏ برای هر صفحه در ابعاد و موقعیت‌های مختلف محاسبه شد.

کلیدواژه‌ها


عنوان مقاله [English]

Effect of the dimension and position of horizontal stationary rafts on reducing critical submergence of vertical intakes

نویسندگان [English]

  • Navid Nasehi Oskuyi
  • Davood Farsadizadeh
چکیده [English]

Agricultural, urban and industrial demands for water can be supplied by withdrawing water through reservoirs or conveying channels using vertical intakes. This method usually faces with some problems such as vortex flow formation in the inlet. This causes entrainment of air and swirling flow into the intake, which followed by some other difficulties such as reduction of intake capacity and stimulation of vibrations and cavitation inception. In this study, the effect of dimensions and position of the horizontal stationary rafts on the required submergence to suppress surface vortex (with air core) were examined, experimentally. At first some tests were carried out to determine discharge-critical submergence relationship for the condition wihtout any anti-vortex device is used. Then, a dimensionless equation was fitted between relative submergence and intake Froude number. After that, the effect of each raft with a specified dimension and position were examined for five different flow rates. The performance of rafts to reduce required submergence is calculated for each setup. Based on the results, the 2d×2d raft at the position of 1d has the best performance of 29.85%. Finally, a regression equation is fitted to predict relative submergence in the presence of the anti-vortex rafts, with respect to dimensionless parameters of the Froude number, relative plate dimensions and relative installation position.
Agricultural, urban and industrial demands for water can be supplied by withdrawing water through reservoirs or conveying channels using vertical intakes. This method usually faces with some problems such as vortex flow formation in the inlet. This causes entrainment of air and swirling flow into the intake, which followed by some other difficulties such as reduction of intake capacity and stimulation of vibrations and cavitation inception. In this study, the effect of dimensions and position of the horizontal stationary rafts on the required submergence to suppress surface vortex (with air core) were examined, experimentally. At first some tests were carried out to determine discharge-critical submergence relationship for the condition wihtout any anti-vortex device is used. Then, a dimensionless equation was fitted between relative submergence and intake Froude number. After that, the effect of each raft with a specified dimension and position were examined for five different flow rates. The performance of rafts to reduce required submergence is calculated for each setup. Based on the results, the 2d×2d raft at the position of 1d has the best performance of 29.85%. Finally, a regression equation is fitted to predict relative submergence in the presence of the anti-vortex rafts, with respect to dimensionless parameters of the Froude number, relative plate dimensions and relative installation position.
Agricultural, urban and industrial demands for water can be supplied by withdrawing water through reservoirs or conveying channels using vertical intakes. This method usually faces with some problems such as vortex flow formation in the inlet. This causes entrainment of air and swirling flow into the intake, which followed by some other difficulties such as reduction of intake capacity and stimulation of vibrations and cavitation inception. In this study, the effect of dimensions and position of the horizontal stationary rafts on the required submergence to suppress surface vortex (with air core) were examined, experimentally. At first some tests were carried out to determine discharge-critical submergence relationship for the condition wihtout any anti-vortex device is used. Then, a dimensionless equation was fitted between relative submergence and intake Froude number. After that, the effect of each raft with a specified dimension and position were examined for five different flow rates. The performance of rafts to reduce required submergence is calculated for each setup. Based on the results, the 2d×2d raft at the position of 1d has the best performance of 29.85%. Finally, a regression equation is fitted to predict relative submergence in the presence of the anti-vortex rafts, with respect to dimensionless parameters of the Froude number, relative plate dimensions and relative installation position.
Agricultural, urban and industrial demands for water can be supplied by withdrawing water through reservoirs or conveying channels using vertical intakes. This method usually faces with some problems such as vortex flow formation in the inlet. This causes entrainment of air and swirling flow into the intake, which followed by some other difficulties such as reduction of intake capacity and stimulation of vibrations and cavitation inception. In this study, the effect of dimensions and position of the horizontal stationary rafts on the required submergence to suppress surface vortex (with air core) were examined, experimentally. At first some tests were carried out to determine discharge-critical submergence relationship for the condition wihtout any anti-vortex device is used. Then, a dimensionless equation was fitted between relative submergence and intake Froude number. After that, the effect of each raft with a specified dimension and position were examined for five different flow rates. The performance of rafts to reduce required submergence is calculated for each setup. Based on the results, the 2d×2d raft at the position of 1d has the best performance of 29.85%. Finally, a regression equation is fitted to predict relative submergence in the presence of the anti-vortex rafts, with respect to dimensionless parameters of the Froude number, relative plate dimensions and relative installation position.

کلیدواژه‌ها [English]

  • Surface vortex-Stationary rafts-Critical submergence-Vertical intake.-