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اندازهگیری دبی جریان در کانالها با استفاده از سرریز لبه تیز مثلثی 90 درجه با راس همتراز با کف کانال | ||
| تحقیقات مهندسی سازه های آبیاری و زهکشی | ||
| دوره 26، تابستان - شماره پیاپی 99، تیر 1404، صفحه 36-21 اصل مقاله (885.73 K) | ||
| نوع مقاله: مقاله پژوهشی | ||
| شناسه دیجیتال (DOI): 10.22092/idser.2025.369030.1612 | ||
| نویسندگان | ||
| ابراهیم ولیزادگان* 1؛ فرزاد جلیلی2 | ||
| 1گروه علوم و مهندسی آب، واحد خوی، دانشگاه آزاد اسلامی، خوی، ایران. | ||
| 2گروه علوم و مهندسی خاک، واحد خوی، دانشگاه آزاد اسلامی، خوی، ایران. | ||
| چکیده | ||
| سرریزهای لبه تیز مثلثی یکی از ابزارهای کمهزینه و دقیق برای اندازهگیری جریان در کانالها هستند. با وجود ساخت تجهیزات پیشرفته و گرانقیمت اندازهگیری جریان، استفاده از سرریزها بخصوص سرریز لبه تیز مثلثی برای بهرهبرداران از شبکههای آبیاری و آبرسانی انتخاب اول بوده است. روابط محاسبۀ دبی جریان با استفاده از سرریزهای لبه تیز مثلثی برای شرایط خاص نصب این سرریزها توسعه داده شدهاند که یکی از این شرایط قرار گرفتن راس سرریز در ارتفاع معین نسبت به کف کانال (P) است. اما اگر نتوان این ارتفاع را تامین کرد، استفاده از این روابط دقت بالایی نخواهد داشت. در این تحقیق سرریز لبه تیز مثلثی 90 درجه طوری در کانال نصب شد که راس سرریز در محور مرکزی بر کف کانال منطبق شود (P=0). آزمایشهای متعددی در شرایط جریان آزاد و مستغرق صورت گرفت. در شرایط جریان آزاد ضریب C در رابطه Q=CHe2.5 (Q دبی جریان بر حسب متر مکعب بر ثانیه و He ارتفاع مؤثر آب روی راس سرریز بر حسب متر)، برابر 1/5594 شد. برای شرایط جریان مستغرق روابط محاسبه دبی بهدست آمدند. برای ارزیابی صحت روابط بهدست آمده، آزمایشها در کانال آمایشگاهی دیگر تکرار شد و متوسط قدر مطلق خطای نسبی(MARE) روابط بهدست آمده در برآورد دبی جریان در شرایط جریان آزاد 7/7 و در شرایط جریان مستغرق 4/3 درصد تعیین شد. | ||
| کلیدواژهها | ||
| اندازهگیری جریان؛ جریان آزاد؛ جریان مستغرق؛ سرریز مثلثی؛ ضریب دبی | ||
| عنوان مقاله [English] | ||
| Flow Measurement in Canals Using 90 Degree Triangular Sharp Crested Weir With the Vertex at the Same Level to the Bottom of the Canal | ||
| نویسندگان [English] | ||
| Ebrahim Valizadegan1؛ Farzad Jalili2 | ||
| 1Department of Science and engineering of water, Khoy C., Islamic Azad University, Khoy, Iran. | ||
| 2Department of Science and engineering of Soil, Khoy C., Islamic Azad University, Khoy, Iran. | ||
| چکیده [English] | ||
| Introduction Despite the development and construction of advanced equipment for measuring discharge in canals, sharp crested weirs are always used in irrigation and water supply networks due to their simplicity in operation and low cost. Extensive research has been done to obtain the discharge calculation relationship in all types of sharp crested weirs. To increase the efficiency and accuracy of weirs, researchers have performed various researches by applying various changes in the geometry of sharp crested weirs, such as Borghei et al. 2003, Igathinathane et al. 2007, Nicosia et al. 2019, Vatankhah and Khamisabadi 2019, Diwedar et al. 2022, Zeinivand et al. 2024 and other researches. Flow calculation relationships using triangular sharp crested weirs have been developed for the special conditions of installing these weirs, one of these conditions is the location of the vertex of the weir at a certain height from the bottom of the canal (P<0). In this research, a 90 degree triangular sharp crested weir was installed in the canal so that the vertex of the weir be the same level with the bottom of the canal in the central axis (P=0). To find the flow calculation relationship, several experiments were carried out in free and submerged conditions in 2 canals with different floor width. Methodology The modified head-discharge equation for triangular sharp crested weir proposed by Kindsvater and Carter (1957) (Eq. 1) was the basis for conducting experiments and arriving at the discharge calculation relationships in free flow conditions. (1) (2) In the above equations, Q = flow rate, He = effective height of water on vertex of the weir, g = acceleration of gravity, q = angle of the weir vertex, Cd = discharge coefficient, which is affected by the geometry of the weir, H = water height on the vertex of weir and Kh = a quantity that depends on the characteristics of the fluid and the angle of the vertex of weir, and its value is presented in a graph for water at a temperature of 5 to 30 degrees Celsius. In submerged flow conditions, following functional equations were based for conducting experiments and arriving at the discharge calculation equations. (3) (4) Where H1 and H2 = flow depth in the upstream and downstream of the weir respectively, Qs = submerged flow rate, Qf = free flow rate per H1. 10 experiments in free flow and 77 experiments in submerged flow conditions conducted in a flume with a length of 3, width of 0.2 and height of 0.2 meters with an adjustable floor slope in the hydraulic laboratory. To verify the obtained results, all the experiments were repeated again in another flume with a floor width of 25 cm. Results and Discussion Based on equation 1 and experiments in the canal with floor width of 20 cm, the variation of the measured flow (Q) with the theoretical flow (Qtheo.) is shown in Figure 1-a. In order to check the accuracy of the obtained graph and equation, all the experiments were repeated by installing another 90o triangular sharp crested weir in another flume (with a floor width of 25 cm). Based on the these experiments (validation tests), the value of Cd coefficients were obtained as 0.6602 (Fig.1-b), same as fig. 1-a, (Fig.1-b). (a) (b) Fig. 1- variation of the measured flow (Q) with the theoretical flow (Qtheo.), a, in canal with floor width of 20 cm b, in canal with floor width of 25cm Also based on Eq. 3 and 4, the following equations are obtained to discharge calculation under the submerged flow conditions. (5) (6) Conclusions In this research, a 90 degree triangular sharp crested weir was installed in the flume so that the vertex of the weir be the same level with the bottom of the channel in the central axis. After conducting several tests in the canal with a floor width of 20 cm, the relationships for calculating the discharge under free and submerged flow conditions were obtained based on dimensional analysis and the general relationship for calculating the discharge in triangular sharp crested weirs. In order to check the accuracy of the obtained relationships and verify them, experiments were carried out in another laboratory channel with a floor width of 25 cm (both in free flow and submerged flow conditions). The accuracy of the obtained relationships was evaluated using statistical functions of mean absolute value of relative error (MARE) and root mean square error (RMSE) for both channels. Results indicate the high accuracy of discharge calculation relationships both in free flow and submerged flow conditions. Based on the obtained results,both in free flow and submerged flow conditions, the flow permeability of triangular sharp crested weirs with P=0 is higher than weirs with P>0. | ||
| کلیدواژهها [English] | ||
| Discharge coefficient, Flow measurement, Free flow, Submerged flow, Triangular weir | ||
| مراجع | ||
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Ayaz, M.d. & Mansoor, T. (2018). Discharge coefficient of oblique sharp crested weir for free and submerged flow using trained ANN model. Water Science. 32(2). pp. 192-212. Nicosia, A. Serio, M. A. Costanza. A. Di Stefano, C. & Ferro, V. (2024). The stage-discharge relationship of a sharp-crested triangular weir pierced by square orifices. Flow Measurement and Instrumentation. 100.102705. | ||
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