نوع مقاله : مقاله پژوهشی

نویسندگان

• سمیرا طالبی ¹
• قربان مهتابی ²
• مسعود کرباسی ³
• مسعود اکبری ⁴

¹ کارشناسی ارشد سازه‌های آبی؛ گروه مهندسی آب، دانشگاه زنجان، ایران

² استادیار گروه مهندسی آب، دانشگاه زنجان، ایران

³ دانشیار گروه مهندسی آب، دانشگاه زنجان، ایران

⁴ دکتری سازه های آبی، دانشگاه تبریز، تبریز، ایران

چکیده

در سدهای مخزنی، یکی از روش‌های افزایش دبی عبوری سرریزهای مدور قائم و کاهش شرایط وقوع جریان‌های گردابی، اصلاح شکل ورودی سرریز می‌باشد. برای رسیدن به این هدف، سرریز با ورودی نیلوفری، گلبرگی، کلید ‌پیانویی و زیگزاگی پیشنهاد شده است. در این تحقیق شکل جدید ورودی سرریزهای مدور قائم به فرم پاپیونی معرفی شد و با انجام یک سری آزمایش‌، ضریب دبی جریان در این نوع سرریزها مطالعه شد. سرریزهای پاپیونی با زوایای مختلف پاپیون (60 تا 150 درجه) در دو حالت وجود کمان میانی و بدون آن (با طول کلی یکسان سرریز) استفاده و نتایج حاصل با یک سرریز نیلوفری مقایسه شد. نتایج نشان داد که در مدل‌های پاپیونی بدون کمان میانی، افزایش زاویه پاپیون منجر به کاهش تداخل جریان و افزایش دبی عبوری از سرریز می‌شود، به طوری‌که مدل B-150 (با زاویه بین پاپیون برابر 150 درجه) دارای ضریب دبی بالاتری نسبت به سایر مدل‌های پاپیونی بود. این مدل سرریز پاپیونی نسبت به سرریز نیلوفری نیز دارای عملکرد هیدرولیکی بهتری بود (10 درصد). همچنین مزیت اقتصادی آن نسبت به سرریز نیلوفری بالاتر بود (31 درصد). در مدل‌های پاپیونی با کمان میانی، تغییر زاویه پاپیون برروی ضریب دبی جریان اثر محسوسی نداشت و عملکرد هیدرولیکی آنها نسبت به سرریز نیلوفری پایین تر بود (9/7-5/3 درصد).

کلیدواژه‌ها

• سرریز پاپیونی
• سرریز نیلوفری
• شفت قائم
• ضریب دبی

موضوعات

• هیدرولیک

عنوان مقاله [English]

Experimental Study of Hydraulic Properties of Flow over Vertical Shaft Spillway with Bow-Tied Shape Inlet

نویسندگان [English]

• Samira Talebi ¹
• Ghorban Mahtabi ²
• Masoud Karbasi ³
• Masoud Akbari ⁴

¹ University

² Assistant professor, water engineering department, University of Zanjan, Zanjan, Iran

³ Associate professor - university of Zanjan

⁴ University of Tabriz

چکیده [English]

Extended Abstract



Experimental Study of Hydraulic Properties of Flow over Vertical Shaft Spillway with Bow-Tied Shape Inlet



Introduction

A spillway is a structure used to provide the controlled release of water from a dam or levee downstream, typically into the riverbed of the dammed river itself. One of the types of spillway used in dams is vertical shaft spillway or the same as morning glory spillway. One of the methods to increase the flow rate and reduce the occurrence of vortex currents in the spillway is to modify the shape of the inlet of the spillways. In recent years, spillways with daisy, piano key and zigzag inlets have been proposed known as spiral spillways. A review of the results of previous research shows that the common goal in the study of vertical shaft spillways is to pass the flood flows with the highest possible discharge and the lowest water level and reducing the eff destructive effects of vortex currents. In previous researches, issues such as the effect of the inlet type of vertical shaft spillway and geometric parameters of the structure on the discharge coefficient and the study of vortex occurrence conditions and hydraulic flow of vertical shaft spillway. In this research a new shape of vertical shaft inlet in form of Bow-tied spillway was introduced and discharge coefficient of these spillways was investigated using a series of experiments.



Methodology

The experiments of this research were performed in a metal cube tank with 1.5 m length, 1 m height and 1 m width with transparent Plexiglas side walls in the hydraulic laboratory of Department of Water Engineering at Zanjan University. Bow-tied spillways were examined with different angles of the bow-tie (60-150 degree) in both cases of with middle arc and without middle arc and the results were compared with a morning glory spillway. In this research, by preparing eight bow-tie spillways and a morning glory spillway with a total length of 60 cm and considering the hydraulic conditions (H/D), 72 experiments were run to investigate the effect of the geometric shape of the spillway on the discharge coefficient.



Results and Discussion

Results showed that in Bow-tied models without middle arc, increase of the bow-tie angle leads to reduce the flow interference and increase of flow discharge over the spillway. So that B-150 model (with 150 bow-tie angle) had higher discharge coefficient than the other models of bow-tied. This model had better hydraulic performance than morning glory spillway (10 percent). Also, economic advantage of this model was higher than morning glory spillway (31 percent). Results of the tip position of the bow-tie spillway show in tip angle of 120 degree, the tip position of the bow-tie has a significant effect on the discharge coefficient of the spillway, but with increasing the bow tip angle from 120 to 150, the tip position of the bow-tie spillway did not have much effect on the discharge coefficient. In Bow-tied models with middle arc, change of bow-tie angle had no significant effect on discharge coefficient and hydraulic performance of these models was lower than morning glory spillway (5.3-9.7). This could be due to the interference of fall currents and the low internal area of these models.



Conclusions

Comparison of the hydraulic performance of bow-tie models with morning glory spillway shows that the B-150 model has the highest hydraulic performance (10%) compared to other models. On the other hand, this spillway has a better economic advantage (31%) than the morning glory spillway. In the construction of reservoir dams, especially earthen dams, the major part of the executive cost is related to the implementation of concrete structures of emergency spillway. In this situation, by choosing Bow-tied spillway with optimal geometry, a suitable economic savings can be achieved along with improving the hydraulic conditions of the flow.



Keywords: Bow-tied spillway , Discharge coefficient, Morning glory spillway, Vertical shaft

کلیدواژه‌ها [English]

• Bow-tied spillway
• Discharge coefficient
• Morning glory spillway
• Vertical shaft