تعیین ضریب مقاومت جریان در رودخانه ها با بستر شنی (مطالعه موردی: رودخانه شهرچای-ارومیه)

نویسندگان

1 دانش‌آموخته کارشناسی ارشد مهندسی عمران- سازه‌های هیدرولیکی، دانشکده فنی و مهندسی، دانشگاه ارومیه

2 دانشیار دانشکده فنی و مهندسی دانشگاه ارومیه

چکیده

مطالعه و تحقیق در زمینه مقاومت جریان در کانال‌های روباز و رودخانه‌ها پیشینه‌ای طولانی دارد. بکارگیری نتایج حاصل از تحقیقات انجام گرفته در همین راستا، جهت اعمال مدیریت مهندسی در رودخانه‌ها یا کانال‌های روباز با مشخصات هیدرولیکی متفاوت امری ضروری است. هم‌چنین تعیین مقدار بهینه و مناسب ضریب زبری مانینگ تاثیر مستقیم روی تخمین دبی جریان در رودخانه دارد که مهم‌ترین عامل در تصمیم‌گیری برای توسعه پروژه‌های آبی است. در تحقیق حاضر، با اعمال تغییرات در شرایط هیدرولیکی رودخانه، عوامل مؤثر بر مقاومت جریان بررسی شده است. مقدار بهینه ضریب زبری مانینگ رودخانه "شهرچای" با استفاده از مشخصات هیدرولیکی و دانه بندی بستر رودخانه برآورد شده است. ضریب زبری بدست آمده با استفاده از روش‌های مختلف و همچنین مقایسه تصاویر رودخانه شهرچای با رودخانه‌هایی با مشخصات مشابه و زبری معین، واسنجی گردید. با تهیه نقشه‌های سه بعدی منطقه با استفاده از نرم افزار ArcGIS و ایجاد مقاطع عرضی توسطHEC-GEORAS ، مشخصات ژئومتری رودخانه شهرچای محاسبه گردید و به عنوان اطلاعات ورودی به منظور شبیه سازی هیدرولیکی در مدل HECRAS بکار گرفته شد. به ازای ضرایب زبری مانینگ حاصل از روش‌های مختلف شبیه سازی انجام گرفت و مشخصات هیدرولیکی خروجی از مدل‌سازی با مشخصات هیدرولیکی برداشت شده از منطقه، مورد مقایسه قرار گرفت و مقدار بهینه ضریب زبری برای بازه کشتیبان برابر با 032/0 تعیین گردید. نتایج حاصل از این تحقیق نشان می‌دهد که تعیین ضریب زبری مانینگ به سه روش چاو، کاون و مقایسه با تصاویر به لحاظ عوامل متعدد در تخمین ضریب زبری، از دقت زیادی برخوردار هستند.

کلیدواژه‌ها

عنوان مقاله [English]

Determination of Resistance Coefficient in Gravel Bed Rivers (case study: Urmia Shahr-Chay River)

نویسندگان [English]

  • maryam moludi 1
  • Mirali Mohammadi 2
1 MSc. in Civil Eng., Hydraulic Structures, Dept. of Civil Eng., Faculty of Eng., Urmia University, Iran.
2 Department of Civil Eng., Faculty of Eng., Urmia University
چکیده [English]

Applying the studies of resistance to flow in open channels and rivers with specific properties in order to manage them is necessary. An optimum and proper foresight of resistance to flow has a direct impact on the estimation of flow rate, which is important factors in decision about hydro-project developments. This research work tries to identify items which are influencing on the flow resistance by handling properties of the river in specific intervals. In this study, the best Manning’s coefficient of “Shahar-Chay” river by means of hydraulic characteristics and aggregation of river bed has been estimated. Manning’s coefficient by using several methods and using pictures and properties of a river reach with a specific Manning’s coefficient, by comparing to the river conditions with relative pictures and estimating approximate range of the Manning roughness coefficient has been verified. By preparing 3D drawings from region using Arc-GIS and creating lateral sections using Hec-GeoRas, geometric specifications of “Shahar-Chay” river used as input in order to complete hydraulic simulation of HEC-RAS model. By running the software for different values of Manning’s coefficient and hydraulic specifications output from modeling compared to the hydraulic specifications collected from the river reach area. It is found that the most proper value for the Manning coefficient at “Keshtiban” reach is about 0.032. The results of the present research work reveals that three methods, namely “Chaw”, “Coawn” and “comparison of pictures” are more accurate for estimating Manning’s roughness coefficient in rivers, because of introducing several factors taking into account.

کلیدواژه‌ها [English]

  • Flow resistance
  • HEC-RAS
  • Manning roughness coefficient
  • Mathematical model
  • Shahr-chay river

مراجع

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دانش آب و خاک
دوره 31، شماره 4
دی 1400
صفحه 25-37

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