فهرست مطالب

پژوهش آب ایران - پیاپی 24 (بهار 1396)
  • پیاپی 24 (بهار 1396)
  • تاریخ انتشار: 1396/03/16
  • تعداد عناوین: 13
|
  • امیر شریفی، حجت احمدی، کامران زینال زاده صفحه 1
    در این پژوهش،‏ رفتار پوشش های بتنی کانال های آبیاری قرار گرفته روی سه نوع بستر متشکل از خاک بدون مواد افزودنی،‏ خاک دارای آهک 2% و خاک دارای مخلوط 4% سیمان و 4% آهک،‏ با استفاده از مدل پلاکزیس بررسی شده است. به منظور کالیبراسیون مدل از نتایج آزمایش تک محوری انجام یافته روی این سه نوع خاک استفاده شد. ابعاد مختلفی از کانال با پوشش بتنی با شیب های جانبی 2،‏ 5 /1،‏ 1=z بررسی شد و لنگر خمشی وارد بر پوشش بتنی قرار گرفته روی این کانال ها در شرایط مختلف کارکرد کانال شامل انتهای مرحله ساخت،‏ کانال پر و حالت نشت معکوس مقایسه شد. نتایج این بررسی ها نشان می دهد با افزودن 2% آهک و مخلوط (4% آهک و 4% سیمان) به خاک بستر،‏ مقدار لنگرهای وارده به پوشش بتنی بستر به مقدار قابل توجهی کاهش می یابد. این کاهش لنگر خمشی در نمونه دارای مخلوط آهک و سیمان (4% آهک و 4% سیمان) بیشتر از نمونه حاوی آهک 2% تعیین شد. همچنین مقایسه نتایج به دست آمده از تحلیل ها نشان می دهد با افزایش ابعاد کانال لنگرهای خمشی بزرگ تری به پوشش بتنی وارد می شود.
    کلیدواژگان: شیب جانبی، خاک مشکل زا، پلاکزیس، مواد افزودنی، لنگر خمشی
  • مرضیه بهاری، علیرضا عمادی، علی شاهنظری صفحه 13
    بررسی چگونگی حرکت و ته نشینی رسوبات چسبنده،‏ به علت دخالت ماهیت شیمیایی و الکترومغناطیسی ذرات،‏ تحقیق در این زمینه را اندکی مشکل کرده است. این مساله در رودخانه هایی که وجود این ذرات در بار رسوبی آن ها قابل ملاحظه است،‏ باعث تاثیر جدی در برآورد بار رسوبی معلق می شود. هدف از مطالعه حاضر،‏ بررسی تاثیر نانو رس بر تنش برشی بحرانی مصالح چسبنده در کانال های انتقال آب است. آزمایش های هیدرولیکی برای بررسی آستانه حرکت مصالح بستر کانال خاکی C25 (انشعابی از بند انحرافی گنج افروز در محدوده پروژه البرز) و همچنین بررسی عملکرد نانو رس بر فرسایش خاک انجام شد. نتایج نشان داد مقدار تنش برشی بحرانی و سرعت بحرانی رسوبات بعد از اختلاط رسوب با نانو رس به ترتیب به میزان 50 و 71 /12 درصد افزایش یافت. در نتیجه از آن جایی که افزایش تنش برشی بحرانی نشان دهنده پایداری بیشتر ذرات در مقابل فرسایش است؛ بنابراین با کمک نانو رس ها می توان بر مشکلات ناشی از فرسایش و رسوب گذاری در کانال ها و حتی رودخانه ها فایق آمد.
    کلیدواژگان: نانو رس، کانال، تنش برشی، فرسایش، رسوبات چسبنده
  • علی سرگلزایی، ام البنی محمدرضاپور، زهرا دهقان صفحه 21
    ماهیت پیچیده مسائل آب،‏ رشد سریع جمعیت،‏ نیاز به آب برای مصارف مختلف و منابع محدود آب برای تامین نیازها،‏ نیازمند روش های جدیدی است که دیدگاه های فنی،‏ اقتصادی،‏ زیست محیطی و اجتماعی را در یک قالب به هم پیوسته گردآوری کند. برای مدیریت و برنامه ریزی بهینه منابع آب مدل WEAP به دلیل جامعیت و سیستم مدیریت یکپارچه منابع آب مورد توجه بسیاری از محققان قرار گرفته است. هدف از انجام این پژوهش،‏ تعیین مقدار آب تخصیص یافته برای بخش های کشاورزی،‏ شرب وتالاب هامون با استفاده از مدل WEAP از مخازن چاه نیمه و برنامه ریزی های مدیریتی در شرایط توسعه و موجود در قالب سناریو های مدیریتی است. در این راستا ابتدا مخازن شبیه سازی شده و سپس مدل برای شرایط پایه و سناریوهای وضعیت موجود و توسعه یافته اجرا گردید. نتایج مقایسه سناریو توسعه (D1) و سناریو مرجع (R) نشان می دهد که برنامه ریزی جدید تخصیص منابع آبی دشت سیستان،‏ با افزایش سطح زیرکشت به میزان 58500 هکتار و تخصیص نیاز زیست محیطی تالاب از مخازن به ترتیب با سطح اعتمادپذیری 7 /48 درصد و 2 /62 قابل تخصیص است. همچنین نتایج نشان داد که اضافه کردن نیاز زیست محیطی تالاب به برنامه ریزی نسبت به سناریوی وضع موجود با ثابت ماندن سطح اعتماد پذیری در تخصیص آب به سایر بخش ها،‏ تهدیدی برای تامین نیاز بخش های دیگر به وجود نمی آورد.
    کلیدواژگان: مخازن چاه نیمه، تخصیص منابع آب، تالاب هامون، اعتمادپذیری، مدل WEAP
  • محمدرضا ریاحی، کریم سلیمانی، سیدرمضان موسوی، معصومه بنی هاشمی صفحه 33
    یکی از عوامل تاثیرگذار در تغییر روند رژیم جریان رودخانه ها،‏ تغییر کاربری اراضی در سطح حوضه است. در این مطالعه برای بررسی تغییرات کاربری اراضی حوضه،‏ از تصاویر سنجنده های TM لندست و LISS III ماهواره IRS-1D مربوط به سال های 1984 و 2012 در محیط نرم افزارهای پیشرفته سامانه اطلاعات جغرافیایی (GIS) و سنجش از دور (RS) استفاده شده است؛ به گونه ای که پس از اعمال تصحیح ها و آنالیزهای مختلف بازسازی و نمونه برداری تصادفی از واحدهای کاربری اراضی،‏ طبقه بندی برای هر دو تصویر با استفاده از الگوریتم حداکثر احتمال انجام شد. با پردازش های مختلف،‏ بهترین ترکیب باندی،‏ باندهای 1،‏ 4 و 7 تصویر TM با ضریب کاپای 86 /0،‏ ضریب کلی 75 /92 و باندهای 2،‏ 3 و 4 تصویر LISSIII با ضریب کاپای 87 /0،‏ ضریب کلی 47 /91 انتخاب شد. نتایج این پژوهش نشان می دهد که در این دوره 28 ساله،‏ سطح جنگل های زیرحوضه لکشا به مقدار 1042 هکتار (79 /4%) کاهش،‏ 297 هکتار (33 /34%) از اراضی بدون پوشش گیاهی و 745 هکتار (63 /28%) از اراضی کشاورزی نیز افزایش یافته است. نتایج حاصل از واسنجی مدل پس از بهینه سازی پارمترهای شماره منحنی و زمان تاخیر حوضه نشان داد که تغییر کاربری اراضی در این فاصله زمانی،‏ میزان دبی اوج و رواناب را در محل خروجی حوضه به ترتیب از 5 /36 مترمکعب بر ثانیه و 4 /78 میلیون مترمکعب در سال 1984 به 9 /69 مترمکعب بر ثانیه و 55 /119 میلیون مترمکعب در سال 2011 افزایش داده است.
    کلیدواژگان: واسنجی مدل، دبی، HEC، HMS، GIS، کاربری اراضی
  • زهرا بیرانوند، ناصر گنجی خرم دل، حشمت الله آقارضی صفحه 45
    برای کنترل فرسایش خاک و افزایش تولید،‏ کاشت درختان مثمر از طرف آبخیز نشینان انجام می گیرد؛ اما عامل محدود کننده رطوبت است که با جمع آوری رواناب ناشی از بارش می توان آن را تامین کرد. به این منظور از سامانه های استحصال آب باران استفاده می شود. در این پژوهش،‏ سطح جمع آوری کننده آب باران به مساحت 40 مترمربع انتخاب،‏ در انتهای شیب گودالی حفر و نهال بادام کشت شده است.برای ارزیابی کارایی این سامانه ها،‏ به بررسی تغییرات رطوبت پروفیل خاک در چاله نهال های بادام پرداخته شد. به این منظور بلوک های گچی کالیبره شده در آزمایشگاه،‏ در اعماق 30 و 60 سانتی متری کار گذاشته شد. پس از هر بارش که رواناب ایجاد شد،‏ بعد از گاورو شدن زمین،‏ اعداد بلوک با دستگاه رطوبت سنج قرائت شد. برای تجزیه و تحلیل داده ها از شاخص های توصیفی و آزمون های تحلیل واریانس یک طرفه و دانکن استفاده شد. طبق نتایج،‏ بین درصد رطوبت خاک چاله نهال تیمارها در سطح اطمینان 95 درصد اختلاف معنی دار وجود داشت؛ ولی بین درصد رطوبت خاک عمق 30 با 60 سانتی متری در هیچ یک از تیمارها،‏ اختلاف معنی دار مشاهده نشد. با توجه به نتایج،‏ کمترین و بیشترین رطوبت به ترتیب در سامانه مرتع معمولی و سامانه نیمه عایق پلاستیک مشاهده شد. همچنین نتایج نشان داد کاربرد سوپر جاذب در چاله نهال نسبت به شرایط تیمار شاهد،‏ می تواند در افزایش رطوبت خاک برای استقرار و رشد نهال بادام دیم عملکرد بهتری داشته باشد.
    کلیدواژگان: رواناب، رطوبت خاک، نفوذ، بادام دیم، فیلتر شنی
  • حامد نوذری، ندا قشلاقی صفحه 55
    امروزه چالش منابع آب،‏ دغدغه بسیاری از کشورهای خاورمیانه است. این موضوع در ایران،‏ در مورد دریاچه ارومیه که در دهه اخیر دچار بحران شده است،‏ اهمیت دوچندان دارد. با توجه به تغییرات بارندگی،‏ وقوع خشکسالی ها و احداث سدها،‏ تراز سطح آب دریاچه ارومیه دست خوش تغییرات و نوسانات زیادی شده است؛ بنابراین هدف اصلی در این تحقیق،‏ بررسی روش های استوکاستیکی برای شبیه سازی نوسانات و پیش بینی تراز آبی دریاچه ارومیه است تا به کمک آن،‏ بتوان سناریوهایی را برای مدیریت آن تعریف کرد. در ابتدا تراز آب دریاچه،‏ به صورت مستقیم و با استفاده از مدل های سری زمانی در محیط نرم افزار Minitab برای دوره زمانی 32 ساله از سال 1355 تا 1386،‏ شبیه سازی و پیش بینی شد. سپس به مدل سازی دریاچه ارومیه با توجه به رویکرد پویایی سیستم ها در محیط VENSIM پرداخته و پس از آن،‏ شبیه سازی و پیش بینی جریان های ورودی و خروجی به دریاچه با استفاده از مدل های سری زمانی انجام و نتایج پیش بینی وارد مدل شد. مقایسه این دو روش شبیه سازی تراز آب دریاچه ارومیه نشان داد که شبیه سازی جریان های ورودی و خروجی و وارد کردن آن ها در مدل VENSIM نتایج دقیق تری نسبت به شبیه سازی مستقیم تراز سطح آب با استفاده از مدل های سری زمانی در پی خواهد داشت.
    کلیدواژگان: مدل های سری زمانی، پویایی سیستم، تراز آب دریاچه ارومیه، Minitab
  • منا گلابی، بهنام کرمی، محمد الباجی صفحه 65
    در پژوهش حاضر،‏ شبکه های آبیاری و زهکشی تحت پوشش دو شرکت بهره برداری زهره- جراحی و گتوند با استفاده از تحلیل سلسله مراتبی بررسی شدند. بدین منظور شبکه های رجایی،‏ هندیجان،‏ رامشیر،‏ شهید همت شادگان،‏ عقیلی،‏ گتوند،‏ دیمچه،‏ ملاثانی،‏ سلامات و میاناب انتخاب شدند. عوامل سازه ای،‏ آبیاری،‏ زهکشی،‏ اقلیمی،‏ اقتصادی،‏ ارضی و فرهنگی- اجتماعی به عنوان معیارهای اصلی در نظر گرفته و اطلاعات مورد نیاز از شرکت های مذکور و به وسیله ی پرسش نامه های تنظیم شده گردآوری شدند. با استفاده از اطلاعات گردآوری شده و نرم افزار Expert Choice وزن نهایی معیارها،‏ زیرمعیارها و گزینه تعیین گردید. نتایج نشان دادند که از بین معیارهای اصلی،‏ دو عامل سازه ای و آبیاری به ترتیب با 5 /37 و 7 /30 درصد بیشترین وزن را به خود اختصاص داده اند. در بین زیرمعیارها وضعیت رسوب گذاری کانال ها (1 /40%)،‏ نیاز آبی محصول (5 /30%)،‏ وضعیت زهکشی (2 /73%)،‏ تبخیر و تعرق (6 /70%)،‏ قیمت واحد محصول (7 /35%)،‏ وضعیت تجهیز و نوسازی اراضی (1 /31%) و تشکل های آب بران (8 /69%) به ترتیب وابسته به معیارهای سازه ای،‏ آبیاری،‏ زهکشی،‏ اقلیمی،‏ اقتصادی،‏ ارضی،‏ فرهنگی و اجتماعی بیشترین وزن را دارند. از بین زیرمعیارهای بررسی شده صرف نظر از معیار آن ها،‏ وضعیت زهکشی دارای بیشترین وزن نهایی است. همچنین در ارزیابی شبکه های مذکور مشخص شد که شبکه های تحت پوشش شرکت بهره برداری گتوند از شرایط مناسب تری برخوردار هستند.
    کلیدواژگان: معیار، نرم افزار Expert Choice، زیرمعیار، پرسش نامه
  • معصومه فراستی، سمیرا حقیقی، شکوفه برون صفحه 75
    در این پژوهش اثر گیاه نی و پوشال نیشکر بر حذف مس از محلول آبی بررسی می شود. به منظور بررسی حذف مس آزمایش های ناپیوسته انجام و بازدهی جاذب ها در حذف مس از محلول آبی تعیین شد. پارامترهای مختلفی از جمله pH،‏ زمان تماس،‏ جرم جاذب و غلظت اولیه مس روی جذب مس مورد آزمایش قرار گرفت. pH بهینه برای هر دو جاذب برابر هفت،‏ زمان تعادل برای جاذب نی برابر 30 دقیقه و برای جاذب پوشال نیشکر برابر 60 دقیقه و جرم بهینه هر دو جاذب برابر 5 /0گرم به دست آمد. برای جاذب نی و پوشال نیشکر با 5 /0گرم جاذب،‏ به ترتیب بازدهی جذب 34 /87 و 55 /93 درصد به دست آمد. با افزایش غلظت مس (40- 5 میلی گرم بر لیتر)،‏ بازدهی جذب نی از 9 /88 درصد به 5 /42 درصد و برای جاذب پوشال نیشکر از 34 /93 درصد به 8 /89 درصد کاهش یافته است. در بین ایزوترم های مورد مطالعه،‏ فرآیند جذب از مدل ایزوترم لانگمویر تبعیت کرد. از بین مدل های سینتیک داده های آزمایشگاهی با مدل سینتیک لاگرگرن مطابقت بیشتری داشتند. نتایج این مطالعه نشان داد که جاذب پوشال نیشکر اصلاح شده نسبت به جاذب نی،‏ قابلیت بیشتری در حذف یون های مس داشت.
    کلیدواژگان: سینتیک جذب، جذب، حذف مس، مدل ایزوترم
  • محمود محمدرضا پورطبری صفحه 85
    تغییرات درجه حرارت در سدهای بتنی،‏ تاثیر مستقیمی بر خواص ترموالاستیسیته بتن دارد. این تغییرات،‏ تنش و کرنش های ناشی از آن بایستی ارزیابی شدند تا به عنوان بارگذاری اولیه در آنالیز پایداری سد به کار روند. در این پژوهش،‏ برای تعیین پاسخ حرارتی سد بتنی تحت تاثر تغییرات دما،‏ تابش های خورشیدی و آب پشت مخزن سد،‏ از مدل المان محدود سه بعدی آباکوس استفاده شد. برای المان بندی سازه از المان بلوکی چهار وجهی بیست گرهی با شش درجه آزادی که قابلیت تحلیل تنش و تغییر مکان را دارد،‏ استفاده شد. نتایج پارامترهای به دست آمده از تحلیل سه بعدی،‏ همانند جابجایی تاج سد،‏ عمق مناطق ترک خورده و بررسی اثر تغییرات درجه حرارت،‏ نشان دهنده توانایی بالای این روش برای ارزیابی پایداری سد است. تحلیل ها نشان می دهد که حداکثر درجه حرارت و گرادیان دمایی در ناحیه کم عمقی از سطح پایین دست رخ می دهد. همچنین اختلاف درجه حرارت بین نقاط مختلف سطح پایین دست با نقاط هم تراز اطراف به دلیل آثار تابش های خورشیدی قابل توجه است،‏ لذا بی توجه به بهره برداری از مخزن سد،‏ می تواند منجر به بروز ناپایداری و ایجاد ترک در کل بدنه سد شود. بررسی نتایج نشان می دهد مدل پیشنهادی،‏ از دقت مناسبی در پیش بینی رفتار حرارتی سد تحت کنش های محیطی برخوردار است.
    کلیدواژگان: سد بتنی قوسی، المان محدود، تغییرات حرارتی، جابجایی سد، پایداری، بار حرارتی
  • بهزاد قیاسی، روح الله نوری، عبدالرضا کرباسی، ژیکیانگ دنگ صفحه 97
    با وجود مطالعات متنوع در زمینه پیش بینی ضریب انتشار طولی (LDC) در رودخانه های طبیعی،‏ نبود مطالعه ای جامع برای بررسی اثر الگوهای متنوع از پارامترهای هیدرولیکی و هندسی بر این پدیده احساس می شود. همچنین دقت نا مناسب مدل های ارائه شده برای پیش بینی LDC یا کاربرپسند نبودن برخی آنها از دیگر چالش های موجود در این زمینه است. بنابراین هدف اصلی این پژوهش،‏ بررسی الگوهای متنوع پیش بینی LDC با استفاده از تحلیل رگرسیونی است. برای این منظور مراحل واسنجی و صحت سنجی مدل های تخمین LDC با استفاده از الگوهای متنوعی از اطلاعات هیدرولیکی و هندسی چندین رودخانه در آمریکا انجام پذیرفت. نتایج این پژوهش مشخص کرد که از بین الگوهای متنوع ورودی،‏ الگوی شامل پارامتر انحنای رودخانه دارای بهترین عملکرد برای مدل پیش بینی LDC می باشد؛ هرچند که دبی تاثیری بر عملکرد مدل نداشت. همچنین با حذف عدد ثابت از معادله به دست آمده،‏ عملکرد مدل بهبود یافت. مدل مذکور در مراحل واسنجی و صحت سنجی از ضریب تعیین (R2) به ترتیب معادل 993 /0 و 938 /0 برخوردار بود. در نهایت بر مبنای مقایسه بین مدل توسعه داده شده در این پژوهش و دیگر مطالعات،‏ مشخص شد که این مدل دارای عملکرد بهتری نسبت به دیگر مدل ها برای تخمین LDC است.
    کلیدواژگان: رگرسیون غیرخطی، رودخانه، انتشار آلودگی، ضریب انتشار طولی
  • سامان نیک مهر، عاطفه پرورش ریزی، محمدجوآد منعم صفحه 109
    مدیریت و بهره برداری ضعیف در شبکه های آبیاری سبب تحویل و توزیع نامناسب آب در کانال ها و انشعابات شبکه می شود. این پژوهش با هدف ارزیابی عملکرد توزیع آب برای گزینه های بهره برداری مختلف در کانال اصلی شبکه آبیاری کوثر در استان خوزستان انجام شد. شرایط واقعی بهره برداری از کانال به همراه دو سامانه کنترل خودکار شامل کنترل بالادست و کنترل پایین دست با استفاده از مدل هیدرولیکی واسنجی شده،‏ شبیه سازی شد. شبیه سازی برای دو گزینه بهره برداری در طول فصل آبیاری شامل دوره افزایش و کاهش تقاضا انجام شد. با توجه به نتایج شبیه سازی شده،‏ شاخص عدالت توزیع در شرایط بهره برداری کنونی شبکه بیشتر از 2 /0 و عدالت در توزیع آب در طول کانال اصلی بین تمامی آبگیرها در حد ضعیف و نا مناسبی بوده است. کنترل خودکار پایین دست،‏ عملکرد توزیع بهتری نسبت به کنترل خودکار بالادست دارد. همچنین ارزیابی عملکرد گزینه های بهره برداری نشان داد که در دوره افزایش تقاضا،‏ شاخص های بهره برداری دارای وضعیت بهتری نسبت به دوره کاهش تقاضا می باشند.
    کلیدواژگان: شبکه آبیاری کوثر، بهره برداری تقاضامحور، کنترل خودکار، توزیع آب
  • رامتین معینی صفحه 119
    در این پژوهش با استفاده از قابلیت های فرمول بندی جدید الگوریتم بهینه سازی جامعه مورچگان،‏ روشی تک مرحله ای،‏ ابتکاری و بر مبنای قضاوت مهندسی برای حل همزمان مساله طراحی بهینه جانمایی و ابعاد شبکه جمع آوری فاضلاب خانگی پمپ دار و ثقلی ارائه می شود. در الگوریتم پیشنهادی تراز گره های بالادست و پایین دست لوله ها به عنوان متغیر تصمیم مساله در نظر گرفته می شود. با تعیین تراز گره های بالادست و پایین دست لوله ها با استفاده از فرمول بندی جدید الگوریتم بهینه سازی جامعه مورچگان،‏ روشی تک مرحله ای،‏ ابتکاری و بر مبنای قضاوت مهندسی برای تعیین جانمایی شبکه فاضلاب خانگی با شیب معلوم لوله ها ارائه می شود. مسائل نمونه ای با استفاده از الگوریتم پیشنهادی حل شده و با نتایج حاصل از به کارگیری فرم اولیه الگوریتم بهینه سازی جامعه مورچگان در تعیین تراز کارگذاری لوله ها و روشی ابتکاری بر مبنای قضاوت مهندسی در تعیین جانمایی شبکه،‏ مقایسه می شود. نتایج نشان دهنده آن است که الگوریتم پیشنهادی،‏ روشی مناسب در حل مساله طراحی بهینه همزمان جانمایی و ابعاد شبکه جمع آوری فاضلاب خانگی پمپ دار و ثقلی است.
    کلیدواژگان: جانمایی، ابعاد، طراحی بهینه همزمان، فرمول بندی جدید الگوریتم بهینه سازی جامعه مورچگان، شبکه جمع آوری فاضلاب خانگی
  • جواد مظفری، اسدالله محسنی موحد، داود داود مقامی صفحه 129
    بیشتر رودخانه ها در طبیعت پیچان رود بوده و همیشه در حال فرسایش در ساحل خارجی و رسوب گذاری در ساحل داخلی پیچ ها هستند. بنابراین شناخت الگوی جریان و مکان های فرسایش و رسوب گذاری در پیچ ها مهم است. در این پژوهش،‏ به بررسی مدل های ریاضی آشفتگی با نرم افزار فلوئنت پرداخته خواهد شد تا مدل هایی که با داده های آزمایشگاهی هماهنگی مناسبی دارند،‏ برای استفاده در پیچ های مختلف رودخانه ای معرفی شوند. داده های آزمایشگاهی مورد استفاده،‏ کانالی با پیچ تند بوده که در دانشگاه EPFL سوئیس قرار دارد. برای بررسی مدل های آشفتگی،‏ از پارامترهای متوسط گیری شده در عمق استفاده شد. همچنین برای بررسی کمی مدل ها،‏ تعدادی پروفیل سرعت طولی مدل عددی انتخاب شده و با پروفیل های آزمایشگاهی اندازه گیری شده مقایسه شد. نتایج بررسی سرعت طولی متوسط گیری شده در عمق نشان داد که مدل های K-ε،‏ K-ω و RSM توانایی تعیین دقیق نقاط مهم جریان را ندارند. این مدل ها،‏ منطقه جدا شدگی جریان را در زاویه 90 درجه نشان می دهند در حالی که اندازه گیری ها این منطقه را در زاویه 75 درجه مشخص کرده است. اما مدل LES به صورت مناسبی منطقه جداشدگی را نشان می دهد و موقعیت های بیشینه سرعت طولی متوسط گیری شده در عمق را نیز بهتر از سه مدل دیگر مشخص می کند. مقایسه کمی پروفیل های سرعت نشان داد که مدل LES خطای کمتری از دیگر مدل ها دارد و می تواند به عنوان مدل مناسب برای بررسی الگوی جریان در پیچ آبراهه ها استفاده شود.
    کلیدواژگان: نرم افزار فلوئنت، مدل آشفتگی، پارامتر متوسط گیری شده در عمق، پیچ تند
|
  • Page 1
    Since basis contain swelling soil leads to volume changing of soil under concrete linings cause cracking of panels consequently, the operation of irrigation canals would disturb. Chen (1975) and Justo et al (1985) reported that the main causes of irrigation canal failure are volume changing of canal base material in the form of swelling and shrinking. Different methods have been presented to overcome or reduce the risk of such problematic soils to light structures. The magnitude of acting force and bending moments on the canal linings depends upon the canal size and dimension, as well as operating conditions namely full operation or rapid drawdown. Ahmadi et al (2009) recommended that in order to minimize the hazard of concrete cracking the optimum proportion of bed width to canal bottom (B/H) must be followed. Regardless of sidewall slope of the canal, the optimum value for B/H is around 1 to 1.5. However, one of the most popular methods that could be employed to reduce swelling potential of expansive soil is a chemical modification of this kind of soil using by admixtures such as lime and cement. Sahoo and Pradhan (2010) reported the effectiveness of chemical improvement of expansive soils to control and reduce canal failures. Adding admixtures such as lime, cement and fly ash improve soil texture by generating new pozzolan actions (Sahrma et al, 2012). Based on research of Chen (1975) the optimum value for lime content at clayey soil is about 2% to 8% in order to stabilize and reduce expansive potential. Brown and Robinson (1986) conducted a study to determine needed resistance of soil-lime-cement mixture to prevention of seepage. Brown and Sarker (1987) experimentally compared the bending resistance of soil samples improved by lime, cement and lime-cement. The confirmed that the samples contain both admixtures of lime and cement had high strength.
    In this study, the behavior of canal linings constructed on the modified basis via lime-cement chemical admixture has been studied and compared with whom which was constructed on the unmodified bases. In order to study the effect of improved based material on the behavior of canal linings, different content of lime and lime cement were added to soil and experimentally the uniaxial compression test conducted on the samples. The test results show that specimens contain 2% and 4% of lime-cement faced with maximum strength. Therefore, this material selected to involve in analysis of behavior of canal linings, in other words, soil material properties improved via 2% and 4% complex of lime and cement considered as base characteristics. Furthermore, in order to study the acting bending moment and shear forces on the concrete linings numerical simulation of canal behavior was executed using by Plaxis as a finite element base geotechnical model. In order to achieve realistic behavior of canal deformation the complete section of geometry of canal created in the model, nevertheless, the trapezoidal canal section is symmetric and might be considered half. To calibrate the model, uniaxial compression test results were imposed. Different sizes of lined canal with different side slopes equal to z=1, z=1.5 and z= 2 were analyzed and the acting bending moments on the concrete linings under three different conditions, include end of construction, full capacity and drawdown were comprised. Also, the soil behavior considered as elasto-plastic and canal linings as elastic, for both of them Mohr-Coulomb failure envelope were used.
    The results illustrated adding 2% lime and 4%lime mixed with 4% cement lead to significant reduction in the acting bending moments on the concrete linings. Furthermore, the state of 4% of cement and lime in reduction of bending moments on canal lining is more efficient than the specimens with only 2% lime. Also, the compared results showed, the acting bending moments rises with increasing of canal dimension. The comparison between acting bending moment on the canal linings informs that the maximum bending moment acts on the linings in the full operation condition. This state of operation could be considered as critical state for canals constructed where base material be improved via lime-cement complex. Results related to rapid drawdown condition, also, revealed that at the proportion of width of canal to the depth (B/H), between 0.5 to 1 the minimum bending moments would act to linings and this is in agreement with findings of Ahmadi et al (2009).
    Keywords: Lime, cement, Concrete lining, Bending moments, Irrigation canal
  • Page 13
    Study on the movement and deposition of cohesive sediments due to electromagnetic and chemical nature of the particles could be difficult. Estimation of suspended sediment load would also be difficult in the rivers that these particles are present in their sediment load. Cohesive sediments include fine-grained sediments such as silt and clay. These materials have large surfaces that can absorb each other and even other small materials and lead to the formation of aggregate and flocculate structures in low shear stress. Deal with the problem of sedimentation of canals, including issues that should be included in the design and planning of irrigation networks. Considering the recent advances in the use of nano-scale materials, the study of the performance of these materials and their surrounding materials is essential in reducing the bed erosion of the earthen water conveyance canals. For this purpose, nano-clay has been used in this research. In this study, using the experimental data, the effect of nano-clay on the critical shear stress of cohesive materials of bed earthen canals was investigated.
    The used flume was a rectangular canal that its framework was made of iron and its walls were made of glass and plexiglas. Width, length and height of the flume were 50, 1000 and 70 cm, respectively. Discharge of flume was obtained according to the weir discharge-height data. The depth of water inside the flume was measured by the depth gauge. Canal slope was adjustable by an electromotor which was installed below the flume. The flume was placed in different slopes of 0.0005, 0.002, 0.003, 0.006 and 0.008, respectively. The threshold of cohesive bed materials in the earth canal C25 (embranchment of Ganj Afrooz diversion dam located in Alborz Project) was determined using hydraulic experiments; also, the nano-clay effects on soil erosion were evaluated by a hydraulic test. In order to find the threshold of cohesive sediment, erosion was measured by measuring the bulk density of sediments and eroded sediment volume after each experiment. The experiments were carried out by increasing the slope until observing the erosion with high volume. This process was repeated 5 times.
    The relationship between flow shear stress and sediment erodibility was determined in both conditions, before and after adding nano-clay to the soil. With increasing shear stress, the erosion rate increased, However, this increase in the amount of erosion before and after the threshold of sediment was a small amount, but after the moment of sediment threshold, the amount of erosion increased also the gradient of erosion increased several times, that the reason for this was the conversion of erosion from single-clay particles to mass erosion of sediments. The sediment segments which were separated from the bed moved massively at first and after a while, they were crushed into smaller pieces, and the small particles were suspended at the end. By adding nano-clay to the soil, the bulk density of the soil decreased by 10.33% that this was attributed to microstructures with large cavities and to the re-structure of the mass of soils that are combined with nano-particles which was due to the high porosity of micro-particles and nano-particles, inside the particles. Nano-particles, due to their specific surface area and surface load, cause interactions between the particles and lock and fix the particles of the soil, resulting in the formation of relatively thick and massive masses in the soil mass. Due to the continuity of these masses, the critical shear stress and critical velocity sediments after mixing with nano-clay were increased 50 and 12/71%, respectively. After the threshold, due to the integrity of the soil particles, erosion occurred as mass, and this resulted in an increase in the mass and volume of erosion of the sediments after the combination of soil with the nano-clay. As the slope more increased, the erosion increasing was more evident.
    In order to design water canals in areas where the cohesive and fine-grained sediments are high in the combination of sediments entering the canal, instead of using the noncohesive sediment transport criterion, it is better to use the criteria for cohesive sediments such as critical shear stress. As a result, the critical shear stress indicates greater particle stability against erosion so with the help of nano-clay can overcome the problems caused by erosion and sedimentation in rivers or canals.
    Keywords: Shear stress, Erosion, Nano-clay, canal, Cohesive sediments
  • Page 21
    The long history of research on utilization of resources and their allocation to the consuming sectors dates back to the first human efforts in managing his nature in which this exploitation was mostly focused on man (Simonovic, 1992). Now, given the recent droughts in Sistan and due to the fact that the major management of Helmand River occurs in Afghanistan, the Chahnimeh reservoirs in Sistan require special comprehensive management. Therefore, the present study aims to determine the amount of water allocated to the agriculture, potable water, aquaculture, and environmental sectors of quadruplet reservoirs of Chahnimeh.
    Chahnimeh reservoirs are located in East and Northeast of Sistan and Baluchistan province between 61° 29' to 61° 44' east longitude and 30° 40' to 30° 54' north. Water management in decision support system (WEAP) deals with proper setting of priorities and preferences in consumption of resources. Factors considered in this study for water resources’ planning include the environmental need, evaporation, potable water, agriculture, and aquaculture. In this study, the environmental water rights are calculated in accordance with the Montana method (Tennant, 2011). Evaporation from the reservoir’s surface is also calculated based on the monthly curve of volume, level, height, and evaporation at different levels. According to the exponential population, the potable water required for 3 regions of Zabol city, Sistan villages and 30% of the water requirement in Zahedan city was calculated as 3% (Statistical Center of Iran, 1390). Parameters required for agriculture were annual cultivation area and the annual rate of water consumption per hectare. In the reference scenario (R), the regional hydrological conditions were considered as the current conditions, and only the irrigation ability of the 1st, 2nd, and 3rd Chahnimeh was used in water resources planning. Scenario (R1) was created based on the reference scenario (R), but the cultivation level of crops according to the appropriate cropping patterns and drought conditions dropped. In scenario (R2), the required water for other sectors (agriculture and portable) was provided and if there is a suitable opening of the Helmand River, the water requirement of Hamoun wetlands will be provided by the Chahnimeh reservoirs. By relying on the natural flow of the river, after implementing the scenario of development (D), the 4th reservoir tank is added to the previous ones and the cultivation level of agricultural products has increased by 13,500 hectares. In scenario (D1), all hydrological conditions and reservoirs are considered in accordance with the scenario of development and the required water provided from these four reservoirs has been studied. Any violation of system performance from a performance threshold or inability of the system in supplying the required water is called system failure. There are several methods to analyze the performance or failure of the system. In this research, the Reliability index is used to compare the scenarios with each other (Hashimoto et al., 1982).
    This index is determined by calculating the number of failures per requirements during each simulation period. By comparing the scenarios (R1) with (R), the rate of Reliability index in potable water section rises from 90.6% to 96.9%. In the comparison of the scenarios (R2) with (R), the required rate of environmental need of Hamoun wetland in the scenario (R2) was regarded as 10% of monthly input of the Chahnimeh reservoirs, so the results of the model showed that in comparison with the scenario (R), the Reliability index of the system in other sectors remained constant. In comparing the scenarios (D) and (R), the effect of increasing the area under cultivation from 45,000 hectares in the status quo to 58,500 hectares in the development program and addition of the fourth Chahnimeh reservoir to the utilization system of water resources were reviewed. In the scenario (D), the reduced impact of the Reliability index on agriculture and potable water sectors were ignored, so performing agricultural development program under the status quo with a Reliability index of over 98% would be provided. In comparing the scenarios (D1) and (R), the condition of water rights needed for the sectors of agriculture, The purpose of comparing these two scenarios was to assess and analyze the effect of adding the fourth Chahnimeh on the utilization system of water resources and the agricultural development of the region through taking into account the environmental needs of Hamoun wetland in the region. Storage of surplus water in reservoirs could increase water level subject to evaporation. This case was determined by comparing the scenario (D) with the scenario (D1). The results of the simulation showed that evaporation loss in the scenario (D1) was 50 million m3 less than in the scenario (D) in the 4th Chahnimeh. This result also focused on the amount of water released for meeting the environmental needs of Hamoun wetland. In comparison of the scenarios (R2) with (R), considering the water rights as 10% of the water inlet of the Chahnimeh reservoirs would not be a threat to water allocation to other requirements.Under the scenario (R), which represented the current state of the water resources in the region, in 85% of the years, 57.5% of requirements would be provided in the agriculture sector, whereas in the potable water sector, in 85% of the years 87.3% of the needs were met. Under the scenario (D), representing the management development state of water resources in the region, not only the current land under cultivation would be preserved but also13, 500 hectares of agricultural land would be added to the agricultural lands. In this way, in 85% of the years, it would supply 85% of the requirements. Analysis of these scenarios and the results obtained from the scenario (D1) showed that along with the increased needs of the agricultural sector and the Hamoun wetland, in terms of the Reliability level, the development conditions increased more than other scenarios. Moreover, with the addition of the environmental needs of the Hamoun wetland to the water resources’ planning of the region, the rates of evaporation loss from the 4th reservoir could reduce significantly.
    Keywords: Chahnimeh reservoirs, Trust, Hamoon plain, Water resource's allocation, WEAP model
  • Page 33
    Recent research results have shown that many factors such as population growth, extensive land use change, and natural resources destruction caused erosion, soil degradation and also flood. Therefore, hydrologic impacts of vegetation cover management and land use changes on minimum discharges variation, runoff depth, evapotranspiration, soil moisture and a severity of improper exploitation of land and, inappropriate use of land and the peak flow was indicated as the results of environmental changes (Sika et al, 2003). Therefore, a better understanding and assessment of land use change impacts on a watershed hydrologic process is of great importance for predicting flood potential and the mitigation of hazard, and has become a crucial issue for planning, management, and sustainable development of the watershed (Ali et al, 2011). Estimation of flow discharge is one of the important keys for planning and optimal management of water resources at watershed scale such as Laksha catchment in Mazandaran province in the northern part of Iran.
    The study area is located between 36º 46' to 36 º 62' N and 53º 30' to 53º 58' E in the southern and the distance about 8 kilometers of Neka city. The maximum and minimum altitudes of this watershed are 1288 and 73 meters, respectively. The annual precipitation is 640 millimeter according to Paeen Zarandin station for 28 years duration. The annual relative humidity and temperature are 77% and 18Co, respectively. From a map at the scale of 1:25000, the geometric corrections and DEM was extracted which was used to remote sensing data corrections. For the geological data and soil maps, the same scale of 1:50000 was used with sources of the Iranian Geological Survey and Soil and Waters Conservation Organization. The extracted DEM map was produced from the mentioned topographic map with manipulated pixels in ArcGIS software. The dimension of the used DEM for this area was at 15×15 m2 for each pixel. In order to the image classification, firstly, some training area has selected to cover the watershed. Therefore, about 113 points from the study area were marked randomly with the optimum distribution. One of the effective factors in river flow regime variation is related to the basin physical characteristics, slope, vegetation type, geologic formation and land use changes. The land use changes of the study area were gained based on the satellite data of Landsat TM and the IRS-1D LISS-III images of 1984 and 2012 from Neka watershed as the main basin of Laksha sub-basin in advanced ArcGIS version 9.3 and remote sensing software of Envi 4.7. As pre-processing, different corrections were used such as geometric, atmospheric, enhancement and then random sampling was selected for the land classification of each image. The classification technique of maximum likelihood algorithm used to find the best classification method for the used images. The optimum band combination of 7, 4, and 1 from TM image with 0.86 percent of Kappa coefficient had 92.75 overall accuracy, and this combination in LISS-III with bands 2, 3, 4 resulted in 0.87 and 91.47, respectively.
    The results of this research indicated that in the period of 28 years, the forest area was reduced to 1042 hectares (4.79%), the land without vegetation with 297 hectares (34.33%) and 745-hectare area (28.63%) of agricultural land also increased. For this purpose, the land use maps of 1984 and 2012 were integrated with hydrologic soil group maps to find CN in GIS environment. Then in HEC-HMS hydrologic model based on hydrograph curve number and SCS curve number infiltration unit hydrograph method and the surface area of the observed rainfall-runoff data were analyzed for calibration and validation, respectively. The results of the calibrated model parameters were optimized the curve number and lag-time of the watershed. The land use changes in this period influenced on peak flow rate and runoff in the basin outlet from 36.5 m3/sec and 78.4 mil/m3 1984 to 69.9 m3/sec and 119.55 mil/m3 in 2011. Based on the gained results from this study, the main land use change was related to the forest area. This land use change was caused due to the rural population growth and extensive agricultural activities such as tillage in slope direction. The forest area had the dominant land cover of the study area between different land use types. The existence agriculture area, especially the rain-fed land and dispread settlement area among the forest area has evidenced as human activities in landscape. Deforestation and land use changes were the main reason of runoff and flood occurrence in Laksha watershed. The sub-basin of number 1 measured with minimum channel gradient of 3.6% and maximum time of concentration of 201 minutes which expected to have lower peak flow and runoff, but the maximum rate of flow was due to the land use changes such as deforestation in study area based on remote sensing data of Landsat and IRS despite vegetation cover in agricultural type. This result confirmed the last studies of Farajzadeh and Fallah (2008), Saqafian and et al. (2006), Saadati and et al. (2006) and Chen and et al (2009). Finally, it could be concluded that the main reason for the runoff flow in Laksha watershed was related to the land use changes such as deforestation.
    Keywords: Discharge, Flow calibration model, HEC-HMS, GIS, Land use
  • Page 45
    Almost 6.1 billion ha (40%) of the earth's total land surface is dry. Moreover, nearly 5.2 billion hectares are Arid, Semi-Arid and Dry-Subhumid lands that are collectively referred to as drylands. It is estimated that 70% of partially productive drylands are threatened by various forms of degradation, impacting the wellbeing and future of one-sixth of the world population. The accelerated demand for rainwater can be met through the efficient rainwater conservation. In the world, about 73% of the cropland is rainfed. In such situations, rainwater conservation plays a greater role in maintaining and increasing crop productivity. In the rainfed areas, rainwater harvesting and management are assumed as the greater priorities. Water and soil conservation practices for agricultural lands includeinter-terrace rainwater conservation practices, conservation of rainwater at terrace level through bunds and guiding the excess runoff for safe disposal through grassed waterways to the farm ponds/tanks/dams for its storage and recycling to the agricultural lands. These are called hardware measures, which are of the permanent type provided for improvement of relief, physiography and drainage features. These are executed with major Government support with the purpose to check soil erosion, regulate overland flow and reduce peak flow. The present approach is to reduce runoff by adopting suitable management practices includeing, tillage practices comprising primary tillage operations i.e. summer or deep ploughing either every year or once in three years depending upon the soil type, land smoothening to avoid local depressions, frequent harrowing and secondary tillage practices with frequent inter-cultivations. Rainwater harvesting is a method of gathering and storing of rainwater. This method has been used to provide water for drinking, livestock, irrigation or refilling aquifers in a process called groundwater recharge. In some cases, rainwater may be the only available, or economical, water source.
    Use of rainwater harvesting systems, with the goal of supply and increasing soil moisture is considered as a technique of soil and water management. In this study, to evaluate the performance of the systems, the variation of moisture in the soil profile of almond Seedlings irrigated with runoff was investigated in the Markazi province. The dryland and poor grassland are source of water erosion. In order to control the soil erosion and enhance of product, the seedling of fruiting trees was installed in stady parts of the watershed, in the southern slope with the slope of 17%. But the limiting factor was the soil moisture that with runoff collecting from precipitation could be provided. For this purpose, the rainwater harvesting system was used. Plastic lined farm ponds were particularly suitable for those areas where a large quantity of water was lost through seepage, especially where the soil was gravelly and porous. In earthen dams, there is also a common problem of seepage through the embankment. Under such circumstances, to check the seepage from all such types of farm ponds/ earthen dams, the plastic lining is a feasible solution. Polythene sheets of 200 microns were used as lining material for seepage control in the ponds. The sheets were spread at the bottom and on the upstream side, up to the top width of the pond. An average 10 cm thick soil layer also kept the sheet the sheet in proper place, to check external damage and to protect it from exposure to the sun. A permanent and most effective lining material is brick and cement masonry, but it is costlier than other lining materials. In this investigation, for each almond seedling, 40 cubic meter area was selected for collecting rainwater. In order to isolate and seperate the systems, sand filter in seedling hole was applied. The six treatment in the area were established consist of A: the current pasture-Tree hole filled with soil, B: the cleaned surface from bushes and rock-Tree holes filled with soil, C: The cleaned surface from bushes and rock-Tree holes filled with sand filter, D: The semi-isolated plastic and pasture-Tree holes filled with soil, E: The semi-isolated plastic and pasture-Tree hole with sand filter, F: The current pasture-Tree hole filled with super absorbent. In order to measure soil moisture for each treatment after each rainfall event in rain season (2013-2014), the calibrated gypsum block in depth of 30 and 60 cm were used. After each runoff, the data of measuring moisture dataset was read. Statistical tests were used in a completely randomized block design with three blocks (replication) each was composed of six treatments. Data analyses were performed based on descriptive statistics and ANOVA and Duncan tests.
    According to the results, a significant difference was observed between the repetitions of each treatment. The soil moisture percentage between planting hole's treatments was with significant at 95 percent confidence level. But this percentage between depths of 30 and 60 cm hadn’t significant difference. The results showed the minimum and maximum of harvesting runoff and soil moisture percentages were in current rangeland and plastic semi-insolation systems, respectively. Also, results showed that the use of super-absorbent hole can increase soil moisture for seedling establishment and can be acceptable for the growth of dryland almond tree comparing to the current condition.
    Keywords: Dryland almond, Sand filter systems, Infiltration, Soil moisture, Runoff
  • Page 55
    Water is one of the largest challenges in the current century and can be a source of negative and positive changes in the world. In fact, nowadays challenge of water resource is a problem of many countries in the Middle East. Also, lake’s Water level variations are highly sensitive to many environmental forcing such as atmospheric pressure and wind forcing, as well as many other dynamic, presumably nonlinear and interconnected, physical variables. It is a complex phenomenon affected by the natural water exchange between the lake and its watershed, and thus the level reflects the climatic changes within the region. Urmia Lake is the largest inland lake in Iran and the second largest saline lake in the world. Understanding and forecasting water level fluctuations in the Lake is important for a variety of water resource management operations. Because the water level of the lake decreased and its water salinity increased by the decrease of precipitation, droughts, overuse of surface water resources and dams construction. Therefore, forecasting water levels of the Lake has started to attract the attention of the researchers in the country. This paper represents the evaluation of different stochastic methods for simulation and forecasting the lake’s water level.
    This study utilizes two model approaches to predict water levels in the Urmia Lake in Iran: a time series forecasting (Seasonal Autoregressive Integrated Moving Average, SARIMA) model, and a combined SARIMA and system dynamics approach model. System dynamics is one of the most effective methods to evaluate complex systems. It is a computer-aided approach to policy analysis and design. It applies to dynamic problems arising in complex social, managerial, economic, or ecological systems-literally any dynamic systems characterized by interdependence, mutual interaction, information feedback, and circular causality. Mathematically, the basic structure of a formal system dynamics computer simulation model is a system of coupled, nonlinear, first-order differential (or integral) equations. Simulation of such systems is easily accomplished by partitioning simulated time into discrete intervals of length dt and stepping the system through time one dt at a time. A systems dynamics model consists of stocks and flows. A stock is an accumulation of material that has built up in a system over time. The model indicates system status and decisions, so the activities of the system are based on them. A flow is a material that enters or leaves a stock over a period of time. In this study, Vensim system dynamics software was used, as it provides a fully integrated simulation system to conceptualize, simulate, and analyze models of dynamic systems. This modeling tool allows the creation of complex models with greater ease than conventional methods. Also, monthly water level data (a total of 396 observations) was collected for model calibration and validation. The measured data from January 1, 1976, to December 31, 2007 (a total of 372 data sets), was used for calibration, while the data from January 1, 2008, to December 31, 2009 (a total of 24 data sets), was adopted for validation. To evaluate the performances of these models, two different criteria were used to compare the predicted results with the observed data: root mean square error (RMSE) and coefficient of correlation (𝑅). Additionally, The Akaike information criterion (AIC) was used to determined best model fit for the data. Data were analyzed using MINITAB statistical software.
    For time series forecasting, ARIMA (1,1,3) (0,1,2), ARIMA (1,1,4) (0,1,1), ARIMA (1,1,2)(0,1,1) and ARIMA (1,1,3) (0,1,1) were used. According to the performance assessment, it could be found that ARIMA (1,1,2)(0,1,1) yields the best water level prediction with RMSE, 𝑅2, and AIC equal to 0.24 m, 0.74 and -2066.69, respectively. To improve the water level prediction quality, a system dynamics model was utilized to improve the prediction results from Autoregressive Integrated Moving Average model. The results showed that the proposed approach gave the best performance assessment with RMSE and 𝑅2 equal to 0.17 m and 0.75. Therefore, the proposed model was capable of simulating and predicting the lake’s water level. This approach used computer simulation to model a dynamic system that could help to develop scenarios to consider water level fluctuations. Its merits include the increased speed of model development, ease of model improvement, inherent flexibility and more reliable than the conventional methods.
    Keywords: System dynamic, Water level of Urmia Lake, Time series models, MINITAB
  • Page 65
    Study, design, construction and operation of irrigation and drainage networks are small part of the purpose of the network construction. The main purposes are operation, maintenance, optimal efficiency achievement due to performance which are only obtained by monitoring and evaluation of networks. Evaluating performance of irrigation and drainage, if it based on a personal idea, will limit by the comparison of simple indicators such as yield per unit area. But many groups are involved in irrigation and drainage networks. So the methods which consist of wide range of information and ideas should be applied. Khuzestan province, with an area equal to 64, 057 square kilometers in the southwest of Iran has third of total surface water resources of Iran. Existence five Main River (Karoon, Dez, Karkheh, Maroon and Zohreh-Jarahi) and fertile lands are the most important natural features in Khuzestan province. In contrast to, high levels of land salinity and water table are the limiting factors for agricultural activities. In addition, in this area agricultural products can be planted in the four seasons of the year. Development of agriculture in this region with saline soils, ground water and climatic conditions requires design, implementation, operation and maintenance of the irrigation and drainage networks. In recent years, significant measures have been done in this regard. Unfortunately after construction, due to lack of evaluation and monitoring systems despite the huge costs of the network, the desired result have not obtained. There are various methods for evaluating systems. One of these tools is analytical hierarchy process. In this method are used complex of criteria, sub-criteria, options and the idea of different kind of person who related to the subject.
    To evaluate the irrigation and drainage networks of Khuzestan Province was used analytical hierarchy process. For this purpose, the irrigation and drainage networks of Zohreh-Jarahi and Gotvand companies were selected. The networks consisted of Shahid Rajae, Hendijan, Ramshir, Shahid Hemat of Shadeghan, Aghili, Gotvand, Daymcheh, Molasani, Salamat and Mianab. In order to evaluate the networks, criteria, sub-criteria and options were defined. Seven factors including; structure, irrigation, drainage, climate, economy, territorial and socio-cultural were chosen as criteria. Finally, 29 factors were selected as sub-criteria for evaluation of ten options. In order to select the criteria, sub-criteria and options the experiences and references were used. For collecting the information, a total of 100 questionnaires based on the criteria and sub-criteria were completed. According to the results of the questionnaire, geometric matrix of the main criteria, sub-criteria and options were formed. Then the information was transferred to Export Choice software and weight of the criteria, sub-criteria and options were determined.
    The results showed that the main criteria for both structural factors and irrigation have the highest weight equal to 37.5% and 30.7% respectively. Among the sub-criteria, the canals sedimentation (40.1%), crop water requirement (30.5%), the drainage condition (73.2%), evapotranspiration (70.6%), the price of the product (35.7%), the equipment and the modernization of farms (31.1%) and water user organizations (69.8%) have the highest weight. The sub-criteria is dependent on structural, irrigation, drainage, climate, economy, territorial and socio-cultural factors. In general, regardless of sub-criteria which was evaluated, the condition of drainage had the greatest weight. Current research indicated the importance of attention to sub-criteria for increasing the performance of irrigation and drainage network's efficiency. Sediment of channels, type and condition of gates, type and grade of channels, type and condition of water management structures and channels cover were considered as sub-criteria of structural factor. According to the results, sedimentation in the irrigation and drainage networks had the greatest effect on performance. Unfortunately, the channel dredging was not done according to a regular program and which was depended on the allocation of financial resources, regardless of which sedimentation of channels effect on the valve, water management and other structures. The irrigation criteria consist of water supply, irrigation supply relative allocation of water, crop water requirements, water allocation, water quality and quantity and the method of water distribution in networks. Crop water requirements, water quality and quantity as sub-criteria of mention criteria had the most weight in this group. The consequence showed the undisputed effect of the amount and quality of water in the network and its impact on the network performance, especially from the perspective of consumers. The results of the main criteria of climatic, economic, territorial and socio-cultural showed that evapotranspiration, the unit price of the product, area and water user organizations had the most significant influence on the performance of irrigation and drainage networks in the study region. The results showed that Aghili irrigation and drainage network accordance with the criteria and sub-criteria had the better situations. Also, the assessments of mention networks determined that Gotvand utilization company conditions were favorable as Zohreh-Jarahi Company. Finally, after performing AHP, in addition to the weights, Consistency Ratio (CR) were evaluated. The acceptable result was obtained when the amount of CR was less than 1.0. In the current research, the amount of mention parameter was 0.07 which was indicated acceptable results.
    Keywords: Expert Choice software, Sub-criteria, Criteria, Questionnaire
  • Page 75
    Adsorption processes are widely used by various researchers for the removal of heavy metals from wastewaters and in this type of processes, activated carbon is frequently used as an adsorbent. Many conventional methods including oxidation, coagulation, membrane filtration, reverse osmosis, adsorption, ion exchange, and precipitation have been reported in the literature to be used for the removal of cadmium metals from wastewater. These methods may be ineffective or extremely expensive especially when the wastewaters contain the relatively low concentration of metal (1–100 mg/L) dissolved in a large volume of wastewater. However, adsorption can be considered as one of the most popular methods for the removal of heavy metals from the wastewater due to its low-cost, availability, simplicity of design, and high removal efficiency. Despite its extensive usage in water and wastewater treatment industries, activated carbon remains as an expensive material. In recent years, the need for safe and economic methods for elimination of Cu from contaminated water has directed researche's interest toward the production of other low-cost adsorbents. Therefore, there is an urgent need to find out all possible sources of agro-based inexpensive adsorbents and also for studying their feasibility for the removal of Cu. In this study, the possibility of the utilization of Phragmites australis and sugarcane straw for Cu adsorption was investigated.
    The Phragmites australis plant and sugarcane straw were obtained from Khuzestan Province, southwest Iran. The collected materials were washed with double distilled water and then were used as dry Phragmites and sugarcane straw. The size of microparticles was examined by sieving with a 200 mesh-number sieve. Surface area and surface morphology of the Phragmites australis and sugarcane straw adsorbents were investigated by methylene blue method, scanning electron microscope (SEM), and Fourier-transform infrared spectra (FTIR). FTIR study was carried out to understand surface properties and available functional groups involved in adsorption mechanism.
    All solutions for the adsorption and subsequent analysis were prepared by diluting the prepared stock solution. The initial pH of the Cd solution was changed by adding 0.1 N HCl or 0.1 N NaOH solutions as required. The adsorption experiments were conducted via batch process. The effects of experimental parameters such as initial pH, equilibrium contact time, adsorbent dosage, and initial Cu ion concentration on the adsorption process were investigated. Pseudo-first-order and second-order kinetic models were based on the assumption of physisorption and chemisorption process, respectively. Intraparticle diffusion in liquid-porous solid was explained by surface diffusion, pore volume diffusion, or both of the processes. Diffusion models were also employed to explain the Cd adsorption process. Three main steps are involved in the solid–liquid sorption process occurred between the metal ions and the adsorbent (a) the metal ions are transferred from the bulk solution to the external surface of the adsorbent; this is known as film diffusion, (b) the metal ions are transferred within the pores of the adsorbent; this is known as intraparticle diffusion, occurring either as pore diffusion or as a solid surface diffusion mechanism, (c) the active sites on the surface of the adsorbent capture the metal ions. The FTIR study of fresh adsorbent was carried out to identify the function groups effective in the adsorption process. The results of FTIR indicated the wave numbers for different functional groups present in adsorbents. Aliphatic C–H and C–O stretching may be responsible for Cd adsorption onto P. Australis and sugarcane straw as wave number shifts from 2,918.55 to 2,913.74 cm−1 and 1,058.08 to 1,035.36 cm−1, respectively.
    The Aliphatic C–H and C–O can show cadmium adsorption ability by studied adsorbents.
    Hence, considering the results of FTIR, it was expected that P. Australis and sugarcane straw play a major role in Cd absorption. The results showed that the optimum pH was equal to 7 as the equilibrium time were 30 and 60 min for Phragmites australis and sugarcane straw, respectively. For the two sorbents, as the adsorbent dose increased from 0.1g to 2g, the removal percentage became 93.55% at 0.1g for sugarcane straw and 87.34% at 0.3g for Phragmites australis; however, the other values remained almost constant with the changes in adsorbent dosage, ranging from 0.1g and 0.3 to 2g. With the increase in Cu concentrations (5, 10, 20, 30 and40 mg/L) in Phragmites australis and sugarcane straw adsorbents, percentage removal decreased from 88.9% to 42.5% and 93.34% to 89.8%, respectively. The adsorption kinetics of Cu ions onto Phragmites australis and sugarcane straw was described successfully by pseudo-first-order model. Also, the adsorption behavior of Cu ions fitted Langmuir isotherm. The results of the present study indicated that Phragmites australis and sugarcane straw can be used to remove Cu ions during water treatment process. Compared with Phragmites australis adsorbent, sugarcane straw showed greater capability of Cu adsorption.
    Keywords: Adsorption kinetics, Cu removal, Adsorption, Isotherm model
  • Page 85
    Variation of temperature in concrete dams has a direct effect on the thermo-elasticity properties and creep phenomenon of concrete. These variations also, the stress and strains from them should be evaluated as initial loading used in the stability analysis of the dam. In this study, ABAQUS three-dimensional finite element model used to determine the thermal response of a dam under the effect of air temperature variations, solar radiation and water behind of the dam. So, a structural meshing with tetrahedral element block was used that each element had 20 nodes with 6 degrees of freedom in which there was the ability to analyze the stress and displacement.
    In this research, the air temperature in the format of average daily air temperature was introduced closely as a boundary condition in ABAQUS model. The water temperature is other boundary conditions that were estimated based on the method proposed by Bofang to predict the water temperature at different depths. Also, in this model, the water level as the average daily water level was applied. The amount of displacement and moment of rotation at the level of dam foundation, both essential as boundary conditions, were used as fixed support and equal to zero. The attenuation model of the concrete was considered using the concrete damage plasticity (CDP) criteria with the coefficient of 3%. The modeling of dam foundation was performed according to a ratio of bedrock modulus of elasticity to the modulus of elasticity of concrete dam and using cubic model. The acoustic element was used to reservoir modeling. This element is the best choice in the modeling of water behind of dam. In this study, the considered hypotheses in the analyzing the dam models were as follow: A) Analysis carried out in a time domain, in which the time range of solving problem would be considered from zero to the alternation time. In dynamic analysis (earthquake), the real-time would be entered into the equation's solution. But in the statical analysis, the alternation time would be considered virtual time, and depending on the amount, the time of performing the program could be lower or higher. The software needs this virtual time to solve the equations step by step in different time periods. Generally, to solve a non-linear statically complex problem such as the provided model, it is recommended to analyze these problems by explicit analyzer and it is suggested to consider the entire time of the analysis longer than the alternation time or natural frequency corresponds to the first figure of the vibration mode of problem. Since time or the necessary frequency period for analyzing arc dam commonly is between to 10 to 30 seconds in dynamical analysis; therefore, this time was considered from zero to 20 seconds in the present study. B) Constituent material of the dam was linear, homogenous and viscoelastic.
    The results showed that by thermal modeling, the final displacement direction was toward the reservoir while without thermal analysis and only by hydrostatic force modeling, the hydrostatic pressure tended to displace the dam in the opposite direction. This indicated the effect of thermal changes on the dam body that not only removed the effect of hydrostatic force but also it displaced the body toward the upstream reservoir. Also, the maximum displacement occurred during the warmest month of July and toward the reservoir. Therefore, due to high solar radiation, the slope of the heat changes in areas near the dam’s crest and the downstream areas exposed to sunlight were at high level. The dam body displacements toward the downstream in hot months were more than cold months. This was due to the simultaneous displacements caused by the thermal and hydrostatic loads in cold months. The results of analyzing finite element in different 12 months showed that upstream tensile stress was at low level and as a result, the possibility of cracking due to the static loads is excluded in this area. Based on the average level of the reservoir in 2009, it could be expected that as the water level decrease under the minimum level of the safety operation, the stress level would move from pressure to tensile state and increase the level of the main stresses in the dam body. So the effect of temperature on the creating critical states was assessed more than the effect of the water pressure.
    The results obtained from model parameters such as displacement of dam crest, depth of cracked areas and analyzing temperature variation between different points indicated the high ability of this method for evaluation of the stability of the dam. The analysis showed that the maximum temperature and temperature gradient happen in the shallow area of the downstream level. Also, the temperature difference between different points of the downstream level and the same level point was considerable because of the effects of solar radiation. This could reveal that a lack of attention to operation of dam would lead to the occurrence of instability and cracks in whole arc dam body. The result of the proposed model showed that developed methodology had suitable accuracy in prediction of dam thermal behavior under the environmental actions.
    Keywords: Thermal variation, Thermal load, Arc concrete dams, Displacement of dam, Stability, Finite element
  • Page 97
    Investigating the process of pollutant dispersion in natural rivers is important in pollution control and its distribution and management of aquatic environments. The process of pollution distribution is a function of dispersion coefficient that has been used in Advection-Diffusion equation. Since the one-dimensional models are applied for river water quality modeling, the first step in modeling the quality of river water is determining the Longitudinal Dispersion Coefficient (LDC). Many methods such as empirical, analytical, statistical, field measurements, and more sophisticated approaches, i.e., artificial intelligence techniques have been suggested for LDC estimation. By now, Laboratory methods are associated with many limitations. These methods are along with high costs and detrimental effects on the aquatic environment due to the application of some specific and harmful tracers. Artificial Intelligence Models have had a good prediction for LDC in recent years, but uncertainty in these models, as an annoying factor, always limited their results for practical purposes. These techniques act exactly like a black box model. Also, although different studies have been carried out for LDC estimation in natural rivers, the absence of a comprehensive study to investigate the effects of different patterns of dimensionless hydraulic and geometric parameters on LDC is still felt. Another challenge is the inaccuracy and less user-friendliness of the provided models to predict LDC. Thus, the main objective of this study is to investigate different types of LDC prediction by application of regression analysis.
    The data used in this study for estimation of LDC contains 61 datasets of hydraulic parameters such as velocity U (m/s), shear velocity u*(m/s) and flow rate (Q), and also the geometric specifications measuring in cross-section of rivers like water depth H(m), stream width (W) and curvature of the river σ. This dataset was taken from different sections of 31 rivers in the United States of America. This information was used as input parameters (about 70 percent, i.e 43 data for calibration and 30 percent, i.e. 18 data for testing) for the non-linear regression model.
    Many of researchers have used equations based on establishing a relationship between LDC and hydraulic-geometric specifications of rivers. Some researchers have used other parameters such as Q and σ to improve LDC estimation. So, in this research, all combination of input parameters for application of non-linear equations have been investigated. Non-linear equations could be changed to linear equations by a logarithmic method. Thus, all of the unknown coefficients of equations could be known by a linear Least Squares Regression.
    Calibration and test steps were carried out using various patterns of hydraulic and geometric data of the rivers in the United States of America. The obtained equations have been compared by the statistics of regression method such as coefficient of determination (R2), t-value, p-value and Variance Inflation Factor (VIF). Higher values of t-value led to the lower value of p-value that indicated the importance of parameter in equation. VIF shows the existence of multi-collinearity in equation. Results showed that the pattern including the river curvature parameter had the best performance for LDC prediction model, while discharge parameter had the least effects on the LDC prediction model. Also, if the constant number is eliminated from the equation, the model’s performance is increased. The R2 of calibration and test stages of the best tuned model were 0.993 and 0.938, respectively. Selected equations in this research (with the best performance) compared with the models suggested by other researchers based on Root Mean Square Error (RMSE), Mean Related Error (MRE), Developed Discrepancy Ratio (DDR), and Threshold Statistics (TS) indices. The comparison of the developed model with the past studies revealed that it had a better performance in LDC estimation. Although the model proposed by Zeng and Huai (2014) had the second best performance, its statistical indices (RMSE and MRE)were about 2 and 83 times greater than that those obtained for the developed model. The best model based on the DDR graphic statistic has the largest crest and lowest width. So the comparison of models based on DDR indicated that the developed model in this research had the best performance. Also, the graph of the TS showed that the model developed in this research had the lowest threshold of errors in 100 percent of datasets. Thus, this research provides an LDC estimator model that outperforms the other existence equations.
    Keywords: Non-linear regression, Longitudinal Dispersion Coefficient, River, Pollution Dispersion
  • Page 109
    Poor operation and management of irrigation networks result in inadequate water delivery and distribution in canal and branch of networks. Irrigated agriculture comprehensively uses large volumes of water compared with municipalities and the other sectors, and competition for pure quality water is at any time high in many areas around the world. Thus, it is recognized that amended water management practices in agriculture can result in significant benefits in terms of water availability for expanded agricultural activities and for other usages, and can directly address many environmental problems. Sagacious management of open-canal conduction and delivery systems is necessary to arrive higher water savings in irrigated agriculture. Use of control systems in irrigation network for improving performance in water distribution and delivery to farmers is more suitable. The main objective of a flow canal control system is to optimize the water delivery based on special operational purposes related to water levels or discharges, which are subject to external disturbances. Providing adequate amounts of water is not possible for irrigation areas in arid regions because of the water scarcity. Therefore under this condition, the upstream and the downstream operational systems are not able to meet an equitable water delivery to downstream parts of irrigation networks, as well as to upstream ones. New operational scenarios should be implemented to reclaim water deliveries.
    This study carried out with the aim of performance evaluation of water distribution for different water operational scenarios in the main canal of Kosar irrigation network of Khuzestan Province. The total length of the proposed canal is 20km. The canal has a design discharge capacity of 16.5 m3/s at its head. There are 8 ‘in-line’ check and 15 offtake structures, and 7 cross-structures along the length of the canal. The proposed model was calibrated and validated based on the real data for three conditions consist of the actual condition of operational network, upstream control system and downstream control system. Simulations were carried out for two operational scenarios consist of the increased and decreased demand periods. In order to control the local water level, PI-feedback controller was applied at upstream and downstream of this canal. To reduce the impacts, the pools were coupled in the upstream and downstream direction. The effects were considered by adding decouplers to the controller structure. The control actions, as output, were calculated based on the magnitude of the water level deviation which was taken as input to the controller. The calculated value was added to the upstream gate directly to make a centralized controller. In case of distant downstream feedback control, the water level at the downstream side of a pool was controlled by adjusting the gate at the upstream end of the reach, in reaction to the deviation from the setpoint. The model of the proposed canal was formulated in the SOBEK simulation package. The control system was also programmed in MATLAB. To evaluate the control system potential, simulations were done for one month of the real offtakes schedule. Also, this study presented the evaluation objectives of an irrigation system, its impact on water delivery performance by control systems to improve water management in Khuzestan province by using the performance indicators proposed by Molden and Gates. For these two periods, the mean value of delivery efficiency, adequacy, equity, and reliability performance indicators was estimated.
    The results showed that, for actual condition, the equity index is greater than 0.2 and consequently, it is in poor condition. Also, adequacy and reliability indicators have had poor performance during operation period. Moreover, it is found that the control systems had better performance than operational actual condition. Also, downstream control has bather performance than upstream control. The results indicated that all indicators had better performance in increased demand period than in decreased demand period. For downstream control, distribution and delivery of water happened in shorter time and more uniform over all offtakes which was located in the main canal. For the system after improved, the using control operation for water delivery among irrigation networks was improved water delivery efficiency by improved equitable contribution among irrigation areas through irrigation periods and performed in a constant way could be considered reliable. Based on the evaluation of indicators in this study, it can be concluded that for this main irrigation network, continuous monitoring of the water management and distribution system is difficult by using manual delivery system because there are not any control points to distribute water among them.
    Keywords: Water delivery, Automatic control, Kosar irrigation network, Demand-oriented operation
  • Page 119
    In this paper, a heuristic single phase method with an ad-hoc engineering concept is proposed for simultaneous optimal layout and size design of sanitary pumped/gravitational sewer network using new the formulation of Ant Colony Optimization Algorithm named Arc based Ant Colony Optimization Algorithm (ABACOA). The ABACOA formulation has two significant advantages of efficient implementation of the exploration and exploitation features and also an easy and straightforward definition of the heuristic information, a useful component of the Ant Colony Optimization Algorithm (ACOA), for the ants over the usual form of the ACOA. To solve optimization problem using ACOA, the first and main step is the problem graph definition. Definition a suitable graph for the problem will allow for all feature of the ACOA to be presented. The problem graph is represented by defining decision points, options available at each decision point and the costs associated with each of these options. In the proposed formulation, upstream and downstream nodal elevations of sewer network pipes are taken as decision variables of the problem. With considering the upstream and downstream nodal elevations of the sewer network pipes as the decision variables of the problem, in this formulation, the sewer network pipes are decision points of the problem leading to an easy definition of a new form of the graph. Here, to define the problem graph, the allowable range of the decision variables is discretised into a fixed number of discrete cover depths leading to discrete nodal elevations. The options available at each decision point are defined by the aggregation of all the arcs joining the upstream and downstream nodal elevations of each sewer network pipe. By determination of upstream and downstream nodal elevations of sewer network pipes using ABACOA, a heuristic single phase method with an ad-hoc engineering concept is proposed for layout determination using known pipe slopes as follows. At first, flow direction of each sewer network pipe is defined from the node of higher elevation to the node of lower elevation. It should be noted that, for pipes with nodes of the same elevation, the flow direction is decided upon randomly. Second, by starting from an arbitrary node, each node is checked in turn for the number of leaving pipes. If more than one pipe leaves from the node, the pipe with the steepest slope is considered as the main sewer network pipe and the other pipes should be cut from the network at either end to construct the tree structure for sewer network layout. Finally, a dummy node should be used to define the cut end emphasizing on the existence of the cut. If no pipe leaves from the underlying node, the constructed layout is considered as an infeasible solution. This approach is continued until all nodes are covered leading to construct a directed tree-like layout for sewer network. In order to complete the layout construction, the location of the resulting dummy nodes and corresponding nodal cover depths should be defined. In the proposed method, the cover depths of the dummy nodes are taken equal to those of the adjacency nodes in which it requires that the pipes are cut at the end with higher nodal elevation leading to construct tree layout for sewer network. By determining the nodal cover depths, nodal elevations, pipe slopes and tree-like layout of sewer network, the sewer network pipes diameters should be determined to complete the design process. In the proposed method, the pipe diameters are calculated explicitly such that all the constraints are fully satisfied, if possible. Therefore, by starting the design processes from inlets, the smallest commercially available pipe diameter fully satisfying problem constraints, is taken as sewer pipe diameter. Proposed method is used to solve two hypothetical test examples and the results are presented and compared with those of obtained with using usual form of the ACOA for determination of the upstream and downstream nodal elevations of the sewer network pipes and a heuristic method with ad-hoc engineering concept for layout determination. The results indicate the effectiveness and efficiency of the proposed method to solve the problem of simultaneous optimal layout and size design of sanitary pumped/gravitational sewer network. In other words, while both formulations show good performance for solving the problem of simultaneous optimal layout and size design of sanitary pumped/gravitational sewer network, the proposed ABACOA formulation is shown to produce better results with the same computational effort.
    Keywords: Layout, Simultaneous optimal design, Sizes, Sanitary sewer network, New formulation of Ant Colony Optimization Algorithm
  • Page 129
    Most of the rivers in nature are meandering and they have constantly erosion at outer bank and sedimentation at inner bank with strong secondary current. The water intake should be sited where there is the maximum strength of the secondary flow which causes sediment movement from the inner bank towards the outer bank and the lowest levels of sediment enter into the intake. So, recognizing the patterns and locations of erosion and sedimentation on bends is really important. Moreover, changes in the meanders and their bed and bank erosion causes river bend to move and destruction of the surrounding structures, agricultural farms and adjacent pumping stations; indicating there is a need to understand the flow patterns, maximum secondary flow position and shear stress in river bend using mathematical models. In this research, mathematical models of turbulence were studied using FLUENT software to introduce the models in good agreement with experimental data to use in different bends.
    The experiments were performed in a 1.3 m wide laboratory Plexiglas’s flume consisting of a 193° bend with a constant centerline radius of curvature of R = 1.7 m, preceded and followed by straight reaches 9 m and 5 m long, respectively. The flume was located in the hydraulic laboratory of EPFL, Lausanne, Switzerland. The bed was covered by a quasi-uniform sand with a diameter d = 0.002 m. The curvature ratio R/B = 1.3 which is representative for sharp natural meander bends. The bed was frozen for future examinations after sediment injection for three weeks and forming a developed topography. Fluent software was used for three-dimensional simulation of flow pattern. K-ε, K-ω and RSM Models and LES technique were used to simulate flow patterns. To evaluate the turbulence models, depth averaged parameters were used. Also for Quantitative study of models, some predicted longitudinal velocity profiles were selected and compared with measured velocity profiles. Before performing a calculation using Fluent, a computational domain must be generated to define the geometry of problem. The Gambit software was used for mesh generation. This study comprised of 910,000 computing nodes in the Gambit. This computational grid was obtained finally after size reduction as much as possible and testing several networks in Gambit and then FLUENT software.
    The results of depth averaged velocities showed that K-ε, K-ω and RSM did not have the ability to determine important points of flow and the models showed maximum flow separation zone at 90-degree angle whereas measurements determined the region identified at the angle of 75 degrees. So, there was 15-degree different between RANS model and measurements in flow separation's zone. But the LES model had good agreement with measurements to locate the separation zone. Also, LES model determined longitudinal depth averaged velocity location better than RANS models. Furthermore, about other sections of flow pattern, there were better predictions in LES than others. Between 30 to 60 degree cross sections, LES model had good agreement with experimental measurements and showed maximum velocity moves toward outer bank. Between 60 to 90 degree cross sections, maximum of separation zone predicted by LES places in 75 degree that is near measurements whereas the maximum of separation zone in K-ε, K-ω and RSM models based on Boussinesq equation were in 90 degree cross sections which did not have agreement with the measurements. From 90 to 120 degree cross sections, predictions with LES method was the same as measured flow pattern on channel and maximum velocity places between central line of channel and outer bank. Also, Between 120 to 150 degrees, predicted and measured flow patterns had good agreements with each other. In 120 to 150 degree cross sections, maximum velocity was near central line of channel and moved toward outer bank. From 150 degree cross section toward end of bend, maximum velocity moved and placed in the side of outer bank and had good agreement with measurements. Investigation of LES model showd there was good agreements between predictions and measurements flow patterns whereas K-ε, K-ω and RSM models, named RANS models, did not have good agreement with measurements flow pattern and had more different. Also, Quantitative comparison of depth averaged velocity profiles between experimental results and predictions of models showed that the LES model with 7.9 percent error had the best results than other models. Then K-ε model with 9.6 percent error, RSM Model with 10.4 percent error and K-ω with 10.9 percent error are placed. So, LES model acts better than RANS models on sharp bend and it is usable to predict flow pattern on sharp bend.
    Keywords: Turbulence Models, Fluent Software, Depth-averaged Parameters, Sharp Bend