نوع مقاله : مقاله پژوهشی

نویسندگان

1 استاد، گروه مهندسی عمران، دانشکده فنی و مهندسی، دانشگاه مراغه، مراغه، ایران

2 دانش آموخته دکتری، گروه علوم و مهندسی آب، دانشکده کشاورزی، دانشگاه تبریز، تبریز، ایران

3 گروه مهندسی عمران، دانشکده فنی و مهندسی، دانشگاه مراغه، مراغه، ایران

چکیده

در پژوهش حاضر ضریب انقباض، ضریب‌دبی، طول پرش هیدرولیکی و افت انرژی نسبی که در آن دریچه به‌عنوان مولد جریان فوق بحرانی عمل می‌کند، در بازشدگی‌های مختلف مورد بررسی قرار گرفت. بیشترین مقدار ضریب انقباض مربوط به دریچه با کم‌ترین مقدار بازشدگی می‌باشد. میزان بازشدگی دریچه با ضریب‌دبی جریان رابطه معکوس دارد. در یک دبی مشخص، افزایش بازشدگی منجر به کاهش استهلاک انرژی نسبی می‌گردد. همچنین با افزایش عدد فرود بعد از دریچه افت انرژی نسبی افزایش پیدا می‌کند. در پژوهش حاضر دامنه عدد فرود بعد از دریچه از 2/2 تا 14/2 تغییر کرده است که تأثیر مستقیمی بر طول پرش هیدرولیکی دارد و با افزایش بازشدگی، عدد فرود و طول پرش کاهش می‌یابد. میزان بازشدگی دریچه با عمق آب بالادست و نیروی هیدرودینامیکی وارد بر دریچه رابطه عکس دارد. روابط چند جمله‌ای غیرخطی رگرسیونی برای پیش‌بینی افت انرژی نسبی و ضریب‌دبی با نتایج مناسب شاخص‌های آماری خطای جذر میانگین مربعات و شاخص کلینگ گوپتا ارائه شد. برای ضریب‌دبی بیش از 78% داده‌ها دارای خطایی کم‌تر از 1/5±% محاسبه شد. همچنین برای افت انرژی نیز نسبت به بالادست و پائین‌دست، بیش از 88% داده‌ها به‌ترتیب دارای خطای نسبی کم‌تر از 5±% و 1±% می‌باشند. شاخص کلینگ گوپتا در محدوده بسیارخوب قرار گرفت.

کلیدواژه‌ها

موضوعات

عنوان مقاله [English]

Experimental Investigation of Hydraulic Parameters of Flow in Sluice Gates with Different Openings

نویسندگان [English]

  • Rasoul Daneshfaraz 1
  • Reza Norouzi 2
  • Hamidreza Abbaszadeh 3

1 Professor, Department of Civil Engineering, Faculty of Engineering, University of Maragheh, Maragheh, Iran.

2 Water Engineering Department, University of Tabriz, Tabriz, Iran

3 Department of civil engineering, engineering faculty, University of Maragheh, Maragheh, Iran

چکیده [English]

Introduction: To prevent water wastage, the control and distribution of water in irrigation networks should be done with utmost care and control structures such as gates should be selected correctly and in accordance with the conditions of each area. In addition, the performance of hydraulic structures in terms of energy dissipation can affect the stability and strength of the structure in the bed of rivers and channels. As hydraulic jump with oscillating waves destroys the structure and the floor of the channel, thus understanding the hydraulic parameters is a fundamental aid to the design of the structure. Therefore, in the present study, with a careful approach to advance the mentioned cases, the need to study sluice gates in order to accurately understand the flow behavior, understanding the effective relationships, and also its effect on hydraulic capacity in different sluice gate openings in supercritical flow conditions was investigated. Also, its effect on contraction coefficient, discharge coefficient, relative energy dissipation, hydraulic jump length, and Froude number in different openings in a wide range of Froude number from 2.2 to 14.2 was studied.

Materials and Methods: Here, an experimental flume with a rectangular cross-section 5 m long, 0.3 m wide and 0.5 m high with walls and floors made of transparent Plexiglas has been used for experiments. The inlet flow to the flume was provided by two pumps, each with a nominal capacity of 450 liters per minute. To read the input flow, Rotameters installed on the flume with a relative error of 2% were used. In the present study, a point gauge with an accuracy of ±1 mm was used to measure the water depth in the flume. Depths were measured at 4 points of cross-section and their average was considered as the final depth.

Results and Discussion: The flow contraction coefficient is inversely related to the gate opening. The values of the discharge coefficient decrease with increasing the opening rate of the sluice gate. On average, the discharge coefficient of 1 cm opening is higher compared to the openings of 2, 4 and 5 cm, 7.75%, 16.51% and 18.35% and maximum 16.62%, 28.9%, and 23.51%, respectively. The results showed that with increasing the Froude number due to decreasing the opening, the relative energy dissipation increases. The results indicated that the relative energy dissipation at the opening of 5 cm had the lowest value and with decreasing the opening, the relative energy dissipation increased. The average energy dissipation relative to the upstream of the hydraulic jump at 1 cm opening is 21.01%, 58.58% and 63.54% more than 2, 4 and 5 cm openings, respectively. Also, this amount is 55.41%, 87.08% and 89.54% for the downstream, respectively. By reducing the amount of opening, the sequent depth at the same discharge is greater than the gate with the larger opening.

Conclusion: The results showed that in different sluice gate openings, the discharge coefficient is inversely related to the gate opening. As the pressure upstream of the gate increases due to the increase in flow, the contraction coefficient decreases. As the sluice gate opening increases, the relative energy dissipation decreases due to the increase in initial depth and consequently the decrease in specific energy in section A, as well as the decrease in sequent depth compared to the gate with lower opening. At the same flow rate, the hydrodynamic force on the gate is inversely related to the amount of gate opening. To calculate the relative energy dissipation and discharge coefficient, non-linear regression polynomial relations were presented in the scope of the present study using Solver in Excel software.

کلیدواژه‌ها [English]

  • Contraction Coefficient
  • Discharge Coefficient
  • Energy Dissipation
  • Gate Opening
  • Hydrodynamic Force