فهرست مطالب

هیدرولیک - سال چهاردهم شماره 3 (پاییز 1398)
  • سال چهاردهم شماره 3 (پاییز 1398)
  • تاریخ انتشار: 1398/09/01
  • تعداد عناوین: 10
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  • بررسی عددی عملکرد سرریزهای پلکانی-کنگره ای بر روی استهلاک انرژی جریان های غیرریزشی
    امیر قادری*، سعید عباسی صفحات 1-16
    یکی از بارزترین مشخصات سرریز های پلکانی، استهلاک انرژی جریان در طول سرریز در اثر انتقال به پایین دست می باشد. هدف از این تحقیق پیشنهاد و معرفی شکل جدیدی از سرریزهای پلکانی برای دستیابی به بیشترین سطح از استهلاک انرژی جریان در انتقال به پایین دست سرریز می باشد. در این تحقیق هیدرولیک جریان عبوری از سرریز پلکانی تحت تاثیر تغییر و اصلاح شکل هندسی پله ها به شکل کنگره هایی از ذوزنقه، مثلثی و مستطیلی به کمک مدل FLOW-3D بررسی شده است. نتایج نشان داد که ایجاد تداخل تیغه های جریان در اثر عبور آب از روی شکل کنگره ای پله ها نکته ی قوت این نوع از سرریزهای پلکانی-کنگره ای می باشد. همچنین شکل کنگره-ای ذوزنقه ای عملکرد بهتری برای دست یابی به بیشترین میزان استهلاک انرژی از خود نشان می دهد. در شرایط جریان یکسان، سرریز پلکانی-کنگره ای مستطیلی، مثلثی و ذوزنقه ای به ترتیب به میزان 4.62، 12.21 و 23.76 درصد در کاهش سرعت جریان و 5.6، 13.1 و 17 درصد در استهلاک انرژی بیشتر نسبت به سرریز پلکانی متعارف موثر بودند. که علت این امر تداخل خطوط جریان و افزایش مقاومت در برابر جریان و همچنین افزایش ناحیه فرآیند گردش مجدد و ایجاد جریان چرخشی بیشتر در این نوع از سرریز های پلکانی جدید می-باشد. این نوع از سرریزها در مقایسه با سرریزهای پلکانی متعارف کمترین هد باقیمانده را دارد. نسبت هد باقیمانده در این سرریزها به طور متوسط برابر 2.57 ≈ Hres/yc و در سرریزهای پلکانی متعارف برابر 4.32 ≈ Hres/yc می باشد. در نهایت می توان از این سرریزها به عنوان نسل جدیدی از سرریزهای پلکانی در جهت افزایش راندمان و عملکرد هیدرولیکی آنها نام و بهره برد.
    کلیدواژگان: سرریز پلکانی-کنگره ای، استهلاک انرژی، تداخل تیغه های جریان، انرژی باقی مانده، Flow-3D
  • روندیابی سیلاب با استفاده از الگوریتم جستجوی گرانشی و بررسی عدم قطعیت پارامترهای هیدرولوژیکی مدل ماسکینگام غیرخطی
    ریحانه اکبری، مسعود رضا حسامی کرمانی*، سعید شجاعی صفحات 17-34
    وقوع سیلاب همواره یکی از نگرانی های بشر در طول تاریخ بوده است. راه های مقابله با این پدیده ویرانگر از اهمیت خاصی در میان محققین برخوردار است. یکی از مقوله های پژوهش در برابر این مساله، روندیابی سیلاب می باشد. از میان روش های گوناگون روندیابی سیلاب، روش هیدرولوژیکی ماسکینگام غیر خطی سه پارامتری از اهمیت زیادی برخوردار می باشد. برای تخمین بهینه پارامترهای مدل غیر خطی ماسکینگام از الگوریتم های تکاملی به جهت سرعت همگرایی و عدم نیاز به تخمین اولیه پارامترهای هیدرولوژیکی استفاده می شود. در این مقاله برای اولین بار از الگوریتم جستجوی گرانشی مبتنی بر الگوریتم کپلر به منظور روندیابی سه هیدروگراف متفاوت استفاده شد. مقایسه نتایج این روش با نتایج تحقیقات قبلی نشان می دهد که الگوریتم ترکیبی استفاده شده در این تحقیق دارای دقت قابل قبول و سرعت همگرایی بالایی می باشد. به منظور بررسی عدم قطعیت پارامترهای مدل ماسکینگام غیر خطی بر اساس تئوری امکان، از الگوریتم ارائه شده در این تحقیق و دیگر الگوریتم ها شامل روش های حداقل مربعات، الگوریتم جستجوی گرانشی، الگوریتم های BFGS ، HJ+DFP ، HJ+CG ، الگوریتم ژنتیک، الگوریتم انتخاب کلونی ایمن، الگوریتم جستجوی هارمونیک و الگوریتم جستجوی هارمونیک بدون تنظیم پارامتر استفاده گردید. توابع عضویت پارامترهای مدل غیر خطی ماسکینگام نشان می دهند که عدم قطعیت پارامتر k از پارامترهای x و m بیشتر است.
    کلیدواژگان: الگوریتم جستجوی گرانشی نخبه گرا، الگوریتم کپلر، تئوری امکان، تابع عضویت مثلثی
  • مدلسازی انتقال محلول در رودخانه حاوی نواحی نگهداشت موقت با استفاده از روش شبکه مدارهای الکتریکی معادل
    آتوسا عطاییان، سیدعلی ایوب زاده*، عبدالرضا نبوی، سالوادور انخل گومز لوپرا صفحات 35-55

    با توجه به آثار زیان بار آلاینده های ورودی به منابع آبی که ناشی از فعالیت های انسانی می باشد، انجام مطالعات در زمینه پیش بینی غلظت این آلاینده ها به منظور انجام اقدامات مقتضی برای کنترل، ضروری به نظر می رسد. بدین منظور مدل های انتقال جرم متعددی برای پیش بینی غلظت محلول در آبراهه های طبیعی ارائه شده اند. این مدل ها به ندرت دارای حل تحلیلی بوده و عمدتا با استفاده از روش های عددی حل می شوند. در این تحقیق روشی تحت عنوان روش شبیه سازی مداری (NSM) که بر پایه آنالوژی موجود بین معادلات دیفرانسیلی حاکم بر پدیده های هیدرودینامیکی و الکتریکی است، معرفی شده و کاربرد آن در حل مدل های مذکور مورد بررسی قرار گرفته است. مراحل اجرای این روش شامل استخراج مدل الکتروآنالوژیکال و طراحی مدار الکتریکی معادل و در نهایت شبیه سازی مدل مداری با استفاده از کد مناسب در یک نرم افزار تحلیل مدارهای الکتریکی است. در این مقاله ابتدا NSM با مدلسازی حالتی از معادله انتقال نگهداشت موقت که حل تحلیلی دارد، صحت سنجی شده و سپس دقت و کارایی آن در مقایسه با روش عددی احجام محدود (FVM) در حل مدل نگهداشت موقت تودرتو، برآورد شده است. نتایج مدلسازی ها حاکی از مطابقت بسیار عالی بین دو روش NSM و FVM با شاخص های خطای نزدیک به صفر است. حال آن که پیاده سازی شرایط مرزی در NSM ساده تر بوده و انعطاف پذیری بالاتری دارد. به علاوه، زمان محاسباتی مورد نیاز NSM برای مثال های مورد مطالعه کمتر از زمان محاسباتی مورد نیاز FVM می باشد. بنابراین NSM به عنوان جایگزینی دقیق و کارا برای روش های عددی در حل معادلات انتقال توام یک بعدی پیشنهاد می شود.

    کلیدواژگان: انتقال جرم، نگهداشت موقت، مدارهای الکتریکی معادل، مدل الکتروآنالوژیکال، روش احجام محدود، رودخانه
  • استخراج یک مدل تحلیلی برای ارزیابی انتقال آلاینده ها از بدنه و مخازن سری بندهای گابیونی
    جعفر چابک پور*، محمد ذبیحی صفحات 55-75
    در این تحقیق سعی شد تا با استفاده از یک مدل آزمایشگاهی و توسعه یک مدل تحلیلی بر مبنای معادلات دیفرانسیل مدل ذخیره موقت، به بررسی کارائی این مدل در فرآیند های انتقال و پراکندگی آلودگی در مخازن سری پرداخته شود. مدل تحلیلی مذکور با استفاده از تبدیل لاپلاس بر روی معادلات دیفرانسیل حل شد و با استفاده از داده های آزمایشگاهی برداشت شده در دو مخزن سری سنگدانه ای، ارزیابی کاملی بر روی کارائی و مقادیر پارامتر های مدل انجام گردید. سدهای ایجاد شده در فلوم آزمایشگاهی با استفاده از سه دانه بندی مختلف با اقطار 1/1، 2/3 و 3/6 سانتی متر ایجاد شد سایر پارامتر های آزمایشگاهی شامل چهار دبی به میزان 7، 9، 11 و 13/5 لیتر بر ثانیه و سه غلظت اولیه تزریقی به میزان 100، 140 و 200 گرم بر لیتر بودند. مقدار متوسط سرعت عبوری، ضریب انتشار طولی و لگاریتم ضریب تبادل جرم مابین منطقه ذخیره ای و بدنه اصلی جریان در جریان عبوری از سد ها با توجه به مدل تحلیلی حاضر به ترتیب برابر با cm/s 4، cm2/s4/2، 5/10- بدست آمد. تطابق منحنی های غلظت-زمان حاصل از حل تحلیلی انجام شده با استفاده از پارامتر های جذر میانگین مربعات خطا و شاخص نش-ساتکلیف مورد ارزیابی قرار گرفت و مقادیر آن-ها به ترتیب برابر با 0/21 و 0/7 استخراج شد که حاکی از قابلیت مطلوب مدل توسعه پیدا کرده برای فرآیند های انتقال و پراکندگی دارد.
    کلیدواژگان: مخازن سری، انتقال و پراکندگی آلودگی، مدل ذخیره ای، تبدیل لاپلاس
  • شبیه سازی عددی تاثیر همگرایی دیواره های شوت بر شکل گیری امواج عرضی در سیستم های تخلیه سیلاب
    سحر بیابانی، مهدی حمیدی*، بهرام نوایی نیا صفحات 75-95
    برخورد جریان با پایه های روی سرریز باعث شکل گیری امواج دم خروسی و توسعه امواج عرضی در طول سیستم تخلیه سیلاب می شود. ازاین رو دستیابی به اطلاعات مربوط به ارتفاع و محل تشکیل این امواج در طراحی دیواره های سرریز بسیار پرکاربرد می باشد. از طرفی در بسیاری از طرح ها برای کاهش هزینه های اجرا ازجمله هزینه های حفاری و بتن ریزی سعی می شود تا شوت به صورت همگرا طراحی گردد و این همگرایی در بسیاری از مواقع موجب به وجود آمدن جریان های عرضی شده که باعث افزایش عمق آب می گردد. بنابراین تحقیق و بررسی در مورد تاثیر زوایای همگرایی سرریز بر عمق و محل تشکیل امواج ضروری به نظر می رسد. در این تحقیق، از نرم افزار Flow3D برای مدل سازی سه بعدی سرریز سد خیرآباد و بررسی تاثیر همگرایی دیواره های شوت بر شکل گیری و توسعه امواج عرضی استفاده شده است. نتایج به دست آمده نشان داد که با افزایش دبی ورودی سرریز و همچنین زاویه همگرایی سرریز، ارتفاع این امواج افزایش می یابد و در برخی موارد به ازای یک دبی ثابت ارتفاع موج به بیش از دو برابر عمق متوسط جریان در مقطع موردبررسی خواهد رسید. نتایج شبیه سازی به ازای یک همگرایی معین نشان داد با افزایش دبی نسبت بیشینه ارتفاع موج به عمق متوسط جریان در همان نقطه، کمتر خواهد شد. به عبارت دیگر در دبی های پایین تر موج عرضی بلندتری نسبت به عمق متوسط تشکیل خواهد شد. همچنین نتایج تحقیق نشان داد با افزایش زاویه همگرایی شوت، علیرغم افزایش ارتفاع امواج شکل گرفته، محل شکل گیری امواج با حداکثر ارتفاع به سمت بالادست شوت منتقل می شود.
    کلیدواژگان: شبیه سازی عددی سیستم تخلیه سیلاب، همگرایی شوت، سد خیرآباد، امواج عرضی، امواج دم خروسی، Flow-3D
  • بررسی عملکرد مدل اتوماتای سلولی در شبیه سازی سیلاب های شهری
    سید عباس حسینی*، سارا نظیف، حسین عباسی زاده صفحات 75-90
    افزایش فراوانی و شدت سیلاب ها در حوضه های شهری باعث ایجاد خسارات جدی به شهرها می شود. یکی از چالش های مهم در تحلیل سیلاب های شهری، شبیه سازی دو بعدی جریان های سطحی ناشی از پس زدگی رواناب از سیستم زهکشی است. بنابراین توسعه یک مدل شبیه سازی سیلاب که بتواند سیلاب را با دقت و سرعت قابل قبول در حوضه های شهری با توپوگرافی پیچیده شبیه سازی و بخش های متاثر از سیلاب را در این حوضه ها مشخص کند از اهمیت بالایی برخوردار است. در این تحقیق یک مدل عددی شبیه سازی سیلاب بر پایه روش اتوماتای سلولی با هدف کاهش زمان و حجم محاسبات نسبت به روش های معمول تحلیل دو بعدی سیلاب، توسعه داده شدهاست. عملکرد مدل اتوماتای سلولی توسعه داده شده در مطالعه حاضر با مدل های هک راس ، مدلی بر پایه معادلات آب کم عمق و مدل تیوفلو که با روش های معمول شبیه سازی هیدرولیکی جریان آب را روندیابی می کنند، در حالات شبیه سازی یک و دو بعدی مورد آزمون قرار گرفته است. همچنین شرایط پایداری با توجه به ابعاد شبکه و اندازه گام زمانی مورد بررسی قرار گرفته است. نتایج این مدل نشان می دهد که روش پیشنهادی با استفاده از داده های توپوگرافی و زبری سطح به عنوان ورودی، با دقت قابل قبول جریان روان آب های سطحی را در حالات یک بعدی و دو بعدی روندیابی می کند. همچنین زمان شبیه سازی جریان در این مدل حدود 60 برابر کمتر از روش معادلات آب کم عمق است.
    کلیدواژگان: سیلاب شهری، اتوماتای سلولی، مدل سازی هیدرولیکی، رواناب سطحی
  • ارزیابی عملکرد هیدرولیکی شبکه آب آتش نشانی پالایشگاه گاز ایلام (رینگ میانی)
    جعفر مامی زاده*، علی کمندی صفحات 90-105
    شبیه سازی هیدرولیکی خطوط انتقال و شبکه های توزیع آب آتش نشانی ابزار مناسبی برای ارزیابی آنها است. در این تحقیق عملکرد شبکه آب آتش نشانی پالایشگاه گاز ایلام (رینگ میانی) با مطالعات میدانی و شبیه سازی هیدرولیکی ارزیابی شد و نیازها و مشکلات این شبکه شناسایی شد. شبکه آب آتش نشانی پالایشگاه به سه ناحیه یا رینگ بالایی، میانی و پایین تقسیم شده است و هر ناحیه وظیفه اطفای حریق بخشی از محدوده پالایشگاه را بر عهده دارد. محاسبات هیدرولیکی خط انتقال آب از منبع آب اصلی پالایشگاه به منبع آب رینگ میانی دارای شیر کشویی در چهار حالت بهره برداری انجام گرفت. سناریوهای مختلف آتش سوزی برای بررسی عملکرد شبکه آب آتش نشانی انجام گرفت. بحرانی ترین سناریو، آتش سوزی در مخازن استوانه ای با سقف شناور است که دبی مورد نیاز جهت اطفاء حریق آن m3/h 1375 است. تحلیل حساسیت نسبت به تغییرات ضریب زبری لوله ها و دبی مورد نیاز در شبکه انجام گرفت. با افزایش20 درصدی زبری، فشار در رینگ 5/3 درصد کاهش یافت. در حالت افزایش دبی مورد نیاز، فشار پمپاژ و دلوج به ترتیب 2/3 و 2/12 درصد کاهش یافت. بازدیدهای میدانی انجام گرفته نشان داد که 20 درصد از شیرهای آتش نشانی شبکه دچار خرابی و نشت هستند. بررسی میدانی عملکرد سیستم خنک کاری مخازن استوانه ای با روشن بودن یک و دو پمپ الکتریکی انجام گردید. بررسی میدانی سیستم فوم مخازن استوانه ای با روشن بودن یک پمپ دیزل انجام گردید. فشار مربوطه در حین مانور در ایستگاه پمپاژ رینگ میانی برابر با 12 بار ثبت شد و این فشار بالا می تواند باعث خرابی تجهیزات رینگ گردد.
    کلیدواژگان: آتش نشانی، پالایشگاه گاز ایلام، شبیه سازی هیدرولیکی، WaterGEMS
  • بررسی رفتار هیدرولیکی و پایداری سد خاکی همگن با زهکش ترکیبی
    اعظم کوه پیما، فواد کیلانه ئی*، محمود حسنلوراد، رضا ضیایی موید صفحات 105-115
    در این پژوهش، استفاده از زهکش ترکیبی بعنوان جایگزینی برای زهکش پنجه‏ای در سدهای خاکی همگن تا ارتفاع 35 متر پیشنهاد و عملکرد آن از منظر هیدرولیکی و پایداری کلی سد بررسی و با زهکش پنجه‏ای مقایسه شده است. برای نیل به این هدف، ابتدا با استفاده از مدل فیزیکی عملکرد هیدرولیکی زهکش ترکیبی مورد بررسی قرار گرفت. پس از اطمینان از تاثیر مثبت این جایگزینی بر عملکرد هیدرولیکی و تطابق مناسب مدلسازی عددی و فیزیکی، آنالیزهای مختلف تراوش و پایداری با مدلسازی عددی به کمک نرم‏افزاری ژئواستودیو انجام شد. به این ترتیب که در مدل‏های عددی ارتفاع زهکش پنجه‏ای بین 20 تا 50 درصد کاهش و بخشی از مصالح باقیمانده بصورت زهکش افقی، با زهکش پنجه‏ای کاهش یافته، ترکیب شد. طبق نتایج، در مدل‏هایی که نصف مصالح باقیمانده از کاهش ارتفاع زهکش پنجه‏ای، در ایجاد قسمت افقی استفاده شده بود، حداقل فاصله‏ی عمود مابین شیب پایین‏دست با سطح آزاد آب در داخل بدنه بین 11 تا 157 درصد افزایش و حجم مصالح زهکش بین 25 تا 50 درصد در مقایسه با مدل‏های دارای زهکش پنجه‏ای کاهش می‏یابد. از طرفی، استفاده از زهکش ترکیبی با عملکرد هیدرولیکی یکسان با زهکش پنجه‏ای، ضمن کاهش 18 تا 60 درصدی حجم مصالح زهکش، علی‏رغم حذف بخشی از مصالح درشت‏دانه که مقاومت برشی بیشتری نسبت به مصالح بدنه دارند، به دلیل سهم کمتر ناحیه‏ی زهکش در طول سطح لغزش و پایین افتادن سطح آزاد آب و افزایش تنش موثر در بخش پنجه، منجر به کاهش حداکثر تا 68/10 درصد در پایداری شیب‏های پایین‏دست گردید.
    کلیدواژگان: سدخاکی همگن، زهکش ترکیبی، تحلیل تراوش، تحلیل پایداری، مدلسازی فیزیکی و عددی
  • مطالعه آزمایشگاهی تاثیر برداشت شن و ماسه از بستر رودخانه ها بر الگوی آبشستگی گروه پایه های پل
    مهدی ماجدی اصل*، رسول دانشفراز، سعیده ولیزاذه صفحات 115-130
    برداشت شن و ماسه، بخصوص از مکان هایی با پتانسیل کمتر، پارامترهای رسوب و جریان اطراف پایه های پل را تحت تاثیر قرار داده و با ایجاد تلاطم و افزایش بار رسوبی در جریان منجر به تاثیرات منفی بر میزان و وسعت آبشستگی حول پایه های پل می گردد. در تحقیق حاضر، تاثیر برداشت مصالح رودخانه ای و پارامترهای هیدرولیکی و رسوبی، بر آبشستگی گروه پایه پل، بررسی گردید. بدین منظور 22 آزمایش در دو دانه بندی مختلف A (قطر متوسط ذرات mm78/0) و B (قطر متوسط ذرات mm78/0)، برای دو حالت بستر با گودال و بدون گودال مورد بررسی قرار گرفت. دو گروه پایه با سه پایه متوالی در راستای جریان در بالادست و پایین دست بستر متحرکی به طول 25/4 متر، درون کانالی به طول 13 متر و عرض 2/1 متر قرار گرفته است. تاثیر برداشت مصالح بر میزان آبشستگی در هر دو قسمت بالادست و پایین دست گروه پایه های مذکور در شرایط جریان زیر بحرانی (محدوده عدد فرود 1/0-5/0) مورد بررسی قرار گرفت. نتایج نشان داد که در اعداد فرود 5/0 برای هر دو مدل A و B، وسعت در پایه اول در بستر بالادست دارای بیشترین مقدار و در اعداد فرود 25/0 نیز برای هر دو مدل A و B پایه چهارم که در بستر پایین دست واقع است، بیشترین وسعت آبشستگی را به خود اختصاص می دهد. بررسی پایین دست گروه پایه ها برای برداشت شن و ماسه، نشان داد که گروه پایه ها به برداشت مصالح از پایین دست خود حساس تر هستند. چراکه با برداشت مصالح از بالادست گروه پایه ، عمق آبشستگی کاهش و برداشت از پایین دست این گروه پایه، عمق آبشستگی را افزایش می دهد.
    کلیدواژگان: الگوی آبشستگی، گروه پای، دانه بندی بستر، برداشت مصالح
  • تحلیل شبه دوبعدی ستون جدایش و بررسی رشد حباب ها در ضربه قوچ
    سیده مریم موسوی فرد*، رضا روحی صفحات 125-135
    در مقاله حاضر، ستون جدایش در لوله های پر فشار تحت تاثیر وقوع ضربه قوچ بصورت عددی با استفاده از مدل-های یک بعدی و شبه دو بعدی گسسته حفره گازی مورد مطالعه و بررسی قرار داده میشود. مدل یک بعدی برپایه روش مشخصه ها مدلسازی شده و از مجموع اصطکاک ناماندگار برونون و اصطکاک شبه ماندگار برای شبیه سازی استهلاک انرژی استفاده می شود. در مدل پیشنهادی شبه دوبعدی، از معادلات مشخصه در راستای محور خط لوله و از معادلات تفاضل محدود در راستای شعاع برای مدل سازی ضربه قوچ استفاده شده و سپس با معادلات حاکمه مدل گسسته حفره گازی کوپل شده و مدل آشفتگی پنج لایه نیز برای شبیه سازی استهلاک انرژی بکار گرفته می شود. همچنین دینامیک رشد حباب ها و روند تغییرات دما و فشار درون حباب ها با استفاده از معادله رایلی-پلست نیز مورد بررسی و تحلیل قرار می گیرد. از مطالعه نتایج مدل ها مشاهده می شود که مدل شبه دو بعدی در محاسبه استهلاک انرژی بویژه در سیکل های پایانی ضربه قوچ موفق تر عمل کرده است.
    کلیدواژگان: ضربه قوچ، ستون جدایش، اصطکاک ناماندگار، مدل شبه دوبعدی، تنش برشی، معادله رایلی-پلست
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  • Numerical investigation of labyrinth stepped spillways’ performance on energy dissipation of skimming flow
    Amir Ghaderi *, Saeed Abbasi Pages 1-16
    One of the main characteristics of stepped spillways is energy dissipation along the spillway during the flow transmission. This research is to propose a new form of spillways’ steps in order to achieve the maximum level of energy dissipation. In this paper flow hydraulics affected by geometric reform of steps to labyrinths with trapezoidal, triangular and rectangular shapes is investigated numerically using FLOW-3D model. The results show that production of flow interferences during flow passing over the labyrinth shapes is the main achievement of labyrinth stepped spillway. Also, trapezoidal labyrinth shape shows a better performance in accessing the maximum energy dissipation. In the same flow condition the rectangular, triangular and trapezoidal labyrinth shaped stepped spillways are effective in flow velocity reduction by 4.62%, 12.21% and 23.76% and also in more energy dissipation by 5.6%, 13.1% and 17% respectively compared to the usual flat stepped spillway. This is because of streamline interference and increasing the resistance against the flow and also the extension of recirculating region and production of more rotational flow. These types of spillways have fewer amounts of the residual head than that for flat stepped spillways. The residual head ratio (Hres/yc) in this type of spillway is ~2.57 while it is ~4.32 in the flat stepped spillway. Finally one can find these types of spillways as next generation of stepped spillways which increases the efficiency and hydraulic performance.
    Keywords: Labyrinth Stepped Spillways, Energy dissipation, Flow interference, Residual Energy, Flow-3D
  • Flood Routing by Gravitational Search Algorithm and Quantify Parameters Uncertainty of Nonlinear Muskingum Model
    Reyhaneh Akbari, Masoud Reza Hessami Kermani *, Saeed Shojaee Pages 17-34
    Introduction The occurrence of flood in the human’s history has always been one of mankind’s concerns. The methods of confronting this destructive phenomenon are of utter importance between researchers. One of the categories against this issue is flood routing. The financial losses of flood to human societies have made it very important to predict the occurrence of floods, so that it is necessary to accurately predict flood. In order to predict the outflows, in fact, the extraction of flood hydrographs is required in the downstream. The routing methods are divided into two hydraulic and hydrological groups. Hydraulic methods require the historical data and the solution of equations mainly through complex hydraulic methods is time consuming, however hydrological methods are preferred because of simplicity of their relative concepts. They are easy to implement and economize time. It is believed to be popular with researchers and has always tried to improve the accuracy of the results of the hydrological methods, which has become a good alternative to hydraulic methods. The Muskingum method is the most widely used hydrological routing technique which is divided into two groups of linear Muskingum and nonlinear Muskingum, depending on the relationship between the amount of storage and the inflows and outflows. Methodology Various methods for estimating the hydrological parameters of Muskingum model have been presented. Techniques for estimating the parameters of the Muskingum model can be classified into three categories: mathematical techniques, phenomenon-mimicking techniques and hybrid algorithms. Among various methods of routing, three parameters nonlinear Muskingum method are hugely popular. Evolutionary algorithms are used to estimate the optimal parameters of the nonlinear Muskingum method because of their convergence rate, no need to make very accurate initial estimate of the hydrological parameters and their randomness nature. In this paper, a gravitational search algorithm which is based on the Kepler algorithm was first used to routing three different hydrographs. In fact, Kepler algorithm is inspired by the elliptical motion of planets around the sun. At different times, the planets are very close to the sun, which represent the stage of the exploration of the algorithm, and at other times the planets are far away from the sun and express the stage of exploitation of the algorithm. Results and discussion Using the combination of gravitational search algorithm and Kepler algorithm (GSA-Kepler), the parameters of the Muskingum model are calculated for routing three different hydrographs: Wilson (1974), Wye River and Veissman and Lewis (2003). The first example is a benchmark problem that was first considered by Wilson (1974) to estimate the parameters of the Muskingum model. This river has no branch to the Belmont and has very little flow. The results of the GSA-Kepler and the Segmented Least Squares Method, BFGS, HJ + DFP, HJ + CG, Genetic Algorithm, Immune Clonal Selection Algorithm, Harmony Search Algorithm and Free Parameter Setting Harmony Search Algorithm are compared with each other. The second example is the flood hydrograph in the Wye River. It has no tributaries from Erwood to Belmont and has very little lateral flow. The third model is a multi-peak flow hygrograph that was first studied by Veissman and Lewis (2003). For the second example, the results of the GSA-Kepler algorithm, COBSA, PSO, DE, GA, BFGS and WOA are showed and for the third example, the results of the GSA-Kepler are compared with the results of the WOA and MHBMO algorithms. After determining the optimal hydrologic parameters, their uncertainty is estimated using the possibility theory. Selecting an analysis of uncertainty depends on many factors, such as knowledge of uncertainty sources and model complexities. There is no definite guideline for choosing the specific uncertainty analysis method that works best. The principles of analyzing the possibility theory are based on fuzzy theory, which was first pronounced by Zadeh in 1965. To investigate the uncertainty of the nonlinear Muskingum model parameters based on the possibility theory, the aforementioned algorithm and other algorithms include Least Squares Method, Gravitational Search Algorithm, BFGS algorithm, HJ + DFP, HJ + CG, Genetic Algorithm, Immune Clonal Selection Algorithm, Harmony Search Algorithm and Free Parameter Setting Harmony Search Algorithm were used. Then three triangular membership functions were assigned to the hydrological variables and the uncertainty of these parameters was calculated using the fuzzy alpha cut method. Conclusion Comparing the results of the GSA-Kepler with the results of the previous studies shows that the combined algorithm used in this study has an acceptable accuracy and high convergence rate. Based on the fuzzy alpha cut method, it is determined that for Wilson (1974) the uncertainty of parameter k is greater than the uncertainty of parameters x and m. Keywords: Membership function, GSA-Kepler, Possiblity theory.
    Keywords: Flood Routing, Gravitational Search Algorithm, Nonlinear Muskingum Method, Uncertainty, Triangle Membership Function, Kepler-GSA algorithm
  • Modeling of Solute Transfer in a River with Transient Storage Zones Using a Network of Equivalent Electrical Circuits
    Atousa Ataieyan, Seyed Ali Ayyoubzadeh *, Abdolreza Nabavi, Salvador &Aacute, Ngel G&Oacute Mez Lopera Pages 35-55

    Human activities everyday release a huge amount of domestic, industrial and agricultural waste into water bodies and continuously change the ecosystem conditions in the world. Considering the harmful effects of these pollutants entering water resources, study about pollution transfer in streams and predicting the pollutant concentration at downstream points seem to be important. For this purpose, the well-known classical advection-dispersion equation (ADE) was presented as the first attempt for describing mass transfer and energy transfer in physical systems. This equation is useful for channels with relatively prismatic and uniform cross-sections. Experimental studies carried out in rivers show that ADE is no longer applicable for natural streams, especially mountain pool and riffle streams because of their irregular cross-sections. Afterward, some more accurate models, referred dead zone models or transient storage models, were suggested by several researchers for predicting solute concentration in natural rivers and calibrated using tracer approach. Such models cause more realistic concentration-time distributions which have lower picks and longer residence time. Solving such models, for which in most cases the analytical solution doesn’t exist, needs numerical methods –methods which usually deal with complexity and is time-consuming. In this study, we have applied Network Simulation Method (NSM) –a powerful and efficient computational method for simulating systems governed by differential equations based on the electric circuit concepts and the analogy between the governing differential equations of hydrodynamic and electrical phenomena– which according to the previous studies simulates desirably the transport of mass in natural streams, to solve two transient storage models. The method consists of two phases of designing and simulating. In designing phase, the system of differential equations corresponding to the prototype must be discretized spatially over the studied domain and then, for each term of the discretized equations the equivalent electrical devices are chosen. These electrical elements are connected based on the algebraic sign of the terms to satisfy Kirchhoff’s current low. Regarding the mathematical models, in most studies, electric potential and electric current are equivalent to the value of the unknown variable and its flux, respectively. The last step of designing the electro-analogical model is the implementation of initial conditions and boundary conditions of unknown variables using appropriate dependent and/or independent, voltage and/or current sources. Simulating this equivalent electrical network is performed through an appropriate electrical-computational circuit code, such as PSpice code. PSpice, which is a powerful circuit analysis software, uses the Newton-Raphson iterative algorithm to solve this set of nonlinear equations and performing the transient analysis. In this paper, NSM is firstly verified by simulating a transient storage transport model developed by Bencala and Walters (1983) for unsteady conservative solute transfer in pool and riffle streams. This model includes two equations for solute concentration in the main channel and in the storage zone and involves one storage zone. The analytical solution for this model has been presented in Laplace domain by Kazezyılmaz-Alhan (2008) considering a hypothetical channel with a constant cross-sectional area, flow velocity, and dispersion coefficient and for two types of upstream boundary conditions including a continuous injection and a pulsating solute injection. The results of this verification were desirable. Then, the accuracy and efficiency of NSM were compared with Finite Volume Method (FVM) –a widely used numerical method in computational fluid dynamics- through simulating an unsteady reactive solute transport using a nested two-storage zone transport model developed by Kerr et al. (2013). This model consists of three equations and involves two storage zones including the surface and hyporheic storage zones interacting together. The results of simulating a hypothetical solute transport problem with this nested model indicate a good match between these two methods with near-zero error indices. The computational time needed for NSM and FVM were 117 seconds and 505 seconds, respectively. So, NSM is much faster. Furthermore, the implementation of boundary conditions in NSM is direct, easier and more flexible. Therefore, NSM is proposed as a precise and efficient alternative for numerical methods in solving one-dimensional coupled differential equations of unsteady transport, simultaneously and providing benchmarks without complex mathematical calculations. Because of its analogical based concept, it can be used as a predicting and monitoring tool for transport phenomena instead of using troublesome physical hydraulic models to perform the water quality studies with less time, low expense and higher accuracy. Hence, in critical conditions, including a sudden spill of a high-hazardous contaminant in a specified point of the river or increasing the concentration of a chemical element to its maximum level, the monitoring and controlling measures at different parts of the river can be carried out with an acceptable accuracy and speed to improve the water quality.

    Keywords: Mass Transfer, Transient storage, Equivalent electrical circuits, Electro-analogical model, finite volume method, River
  • Derivation of an analytical solution for evaluation of the pollution transport in the interconnected reservoirs and rockfill bodies of gabion dams
    Jafar Chabokpour *, Mohammad Zabihi Pages 55-75
    In the present research, it was tried to evaluate the pollution transport in the interconnected reservoirs by deriving a theoretical solution based on the TS model partial differential equations and by conducting an experimental model. The theoretical model has been solved by operation of the Laplace transform to the PDE equations, and a complete evaluation of the model applicability and the parameters’ magnitudes have been fulfilled using experimental data series of two interconnected reservoirs. The created rockfill dams in the laboratory flume have been produced using three different median diameters of the 1.1, 2.3, and 3.6 cm. The other experiment variables were the entrance discharges as 7, 9, 11, and 13.5 l/s and linear source concentration of the 100, 140, and 200 gr/l. The mean values of the velocities, dispersion coefficients, and the logarithm of the mass transfer coefficients between the storage area and the main flow have been determined as 4 cm/s, 2.4 cm2/s, and -10.5 respectively. The corresponding of the experimental breakthrough curves with theoretical ones have been assessed and confirmed using statistical parameters of the RMSE and Nash-Sutcliff, having the values of 0.21 and 0.7, respectively. In the present research, it was tried to evaluate the pollution transport in the interconnected reservoirs by deriving a theoretical solution based on the TS model partial differential equations and by conducting an experimental model. The theoretical model has been solved by operation of the Laplace transform to the PDE equations, and a complete evaluation of the model applicability and the parameters’ magnitudes have been fulfilled using experimental data series of two interconnected reservoirs. The created rockfill dams in the laboratory flume have been produced using three different median diameters of the 1.1, 2.3, and 3.6 cm. The other experiment variables were the entrance discharges as 7, 9, 11, and 13.5 l/s and linear source concentration of the 100, 140, and 200 gr/l. The mean values of the velocities, dispersion coefficients, and the logarithm of the mass transfer coefficients between the storage area and the main flow have been determined as 4 cm/s, 2.4 cm2/s, and -10.5 respectively. The corresponding of the experimental breakthrough curves with theoretical ones have been assessed and confirmed using statistical parameters of the RMSE and Nash-Sutcliff, having the values of 0.21 and 0.7, respectively. In the present research, it was tried to evaluate the pollution transport in the interconnected reservoirs by deriving a theoretical solution based on the TS model partial differential equations and by conducting an experimental model. The theoretical model has been solved by operation of the Laplace transform to the PDE equations, and a complete evaluation of the model applicability and the parameters’ magnitudes have been fulfilled using experimental data series of two interconnected reservoirs. The created rockfill dams in the laboratory flume have been produced using three different median diameters of the 1.1, 2.3, and 3.6 cm. The other experiment variables were the entrance discharges as 7, 9, 11, and 13.5 l/s and linear source concentration of the 100, 140, and 200 gr/l. The mean values of the velocities, dispersion coefficients, and the logarithm of the mass transfer coefficients between the storage area and the main flow have been determined as 4 cm/s, 2.4 cm2/s, and -10.5 respectively. The corresponding of the experimental breakthrough curves with theoretical ones have been assessed and confirmed using statistical parameters of the RMSE and Nash-Sutcliff, having the values of 0.21 and 0.7, respectively. In the present research, it was tried to evaluate the pollution transport in the interconnected reservoirs by deriving a theoretical solution based on the TS model partial differential equations and by conducting an experimental model. The theoretical model has been solved by operation of the Laplace transform to the PDE equations, and a complete evaluation of the model applicability and the parameters’ magnitudes have been fulfilled using experimental data series of two interconnected reservoirs. The created rockfill dams in the laboratory flume have been produced using three different median diameters of the 1.1, 2.3, and 3.6 cm. The other experiment variables were the entrance discharges as 7, 9, 11, and 13.5 l/s and linear source concentration of the 100, 140, and 200 gr/l. The mean values of the velocities, dispersion coefficients, and the logarithm of the mass transfer coefficients between the storage area and the main flow have been determined as 4 cm/s, 2.4 cm2/s, and -10.5 respectively. The corresponding of the experimental breakthrough curves with theoretical ones have been assessed and confirmed using statistical parameters of the RMSE and Nash-Sutcliff, having the values of 0.21 and 0.7, respectively.
    Keywords: Reservoirs in series, advection, dispersion of the pollution, storage model, Laplace transform
  • Numerical simulation of the Chute Convergence effects on Forming the Transverse Wave in Flood Evacuation Systems
    Sahar Biabani, Mehdi Hamidi *, Bahram Navayi Neya Pages 75-95
    Introduction Flow contact with the spillway piers causes rooster tail waves which could continue along the flood evacuation system. Therefore, the information about the height and location of these waves would be useful for the design of the spillway chute walls. On the other hand, the engineers try to design the converging chutes to reduce the excavation costs, and this convergence in many cases would increase the transverse flow depth. According to the literature, three kinds of waves could be formed in the spillway and chute system. The first wave is formed just after the spillway piers and called as rooster tail waves. The Flow passing through the two sides of a pier collide each other at a near distance after the pier and forming the first wave. The second wave is formed at the middle axis of the chute and could be considered as the result of the interaction of the first waves and the channel convergence. The third wave is formed due to the collision of the mentioned waves with the channel walls. Investigating the effect of the chute convergence on the depth and location of transverse waves is critical and necessary and could present suitable information about the three waves. In this paper, the numerical simulation of the Khair Abad dam flood evacuation system is performed for investigating the effects of chute convergence on the formation of the transverse waves along the chute. Methodology In this Research, the FLOW-3D is used for simulation of the effects chute convergence on transverse wave formation. The Khair Abad dam flood evacuation system laboratory tests results were used for verification of the numerical simulation. The present simulations considered four convergence angles of the chute, including 0, 3, 5 and 7 °. Also, the simulation was performed using three discharge rates consist of 3000, 7000 and 9000 m3 / s. The convergence angle of the Khairabad Dam spillway is approximately 5 degrees and the convergence angles were changed during the chute until the chute width reached from 66 m to 40 m. The chute width is kept constant after the convergence. Results and discussion The model validation was performed using the laboratory data of the Kheirabad Dam spillway Model developed by the Iran Water Research Institute. Since the size and number of the cells in the model affect the accuracy of the results and computational cost, this study concentrates in finding the optimum value of dimensions and number of cells for the simulation domain. This procedure could result in acceptable accuracy and suitable computational cost. The results of the verification showed that the smaller grid size and the greater number of cells, result in the higher correlation of the numerical results and the laboratory data. Hence, based on the above-mentioned method and available computational device, the best size and number of the cells were selected for simulating the effect of chute convergence on the three waves height. Simulation results show that the height of the first wave increases with increases in the flow discharge, and the spillway convergence has not a significant effect on the first wave height. Also, the second wave height is increased by the increase in flow discharge. It should be mentioned, the second wave doesn't appear when there is no convergence in the chute, but with increasing the convergence angle the wave height increases and the maximum wave height will move to upstream stations of the chute. In other words, with the increase of the angle of convergence of the chute, the location of the second wave formation will be closer to the spillway crest and its height will increase. The simulation results demonstrated that the increase in the flow discharge could lead to an increase of third waves heights. Also, the results show that the third waves could not be formed when the channel convergence angle is equal to zero, and increase of convergence angle could result in an increase of the third wave height. Also, the increase in the angle of convergence of the chute results in transport of the location of the third wave formation into upstream stations. In other words, the third waves will form closer to the spillway axis by an increase in convergence angle. Numerical simulation results show that the height of the third wave which formed beside the wall can be more than twice the average flow depth at the same point. This fact should be considerate in the design of the chute with convergence. The results also showed that increasing the flow discharge will cause to increase of the wave height, but it led to the decrease of the ratio of the third wave height to the average flow depth. This means that increasing the discharge has less effect on increasing the transverse wave height. Conclusion Simulation results show that the height of transverse waves increases by increasing the discharge. But the ratio of the maximum height of the waves to the average depth of the same station will reduce by the increase of the discharge. Also, Results show that, by increasing the chute’s convergence angle, the height of the transverse waves will increase and the location of the primary transverse waves will transmit to upstream locations of the chute.
    Keywords: Numerical Simulation of Spillway, Chute Convergence, Kheir-Abad Dam, Transverse Waves, Flow-3D, Rooster tail waves
  • Investigation of Cellular Automata Method to Urban Flood Modeling
    Seyed Abbas Hosseini *, Sara Nazif, Hossein Abbasizadeh Pages 75-90
    Increasing frequency and intensity of flooding in urban areas have led to serious damage in urban areas. One of the major challenges in urban flood analysis is the two dimensional simulation of surface runoff caused by surcharged flows from urban drainage systems. Thus, development of an urban flood simulation model, which can rout the water flow on complex topography of urban catchments and determine flooded areas with acceptable computational time and accuracy is very important. In this study, a flood simulation model based on cellular automata approach is developed to reduce time and computational effort in compare with other 2D conventional hydraulic models. The developed model performance is compared with HEC-RAS, shallow water equation and TUFLOW models which simulate the water movement using conventional numerical schemes. Also the model’s stability is assessed by considering different time step and mesh size. The obtained results show that the proposed model, using topographic and surface roughness data as inputs, can simulate water movement with acceptable accuracy one- and two-dimensionally. In addition, the computational time is reduced up to roughly 60 times compared to the model which is based on shallow water equations. Increasing frequency and intensity of flooding in urban areas have led to serious damage in urban areas. One of the major challenges in urban flood analysis is the two dimensional simulation of surface runoff caused by surcharged flows from urban drainage systems. Thus, development of an urban flood simulation model, which can rout the water flow on complex topography of urban catchments and determine flooded areas with acceptable computational time and accuracy is very important. In this study, a flood simulation model based on cellular automata approach is developed to reduce time and computational effort in compare with other 2D conventional hydraulic models. The developed model performance is compared with HEC-RAS, shallow water equation and TUFLOW models which simulate the water movement using conventional numerical schemes. Also the model’s stability is assessed by considering different time step and mesh size. The obtained results show that the proposed model, using topographic and surface roughness data as inputs, can simulate water movement with acceptable accuracy one- and two-dimensionally. In addition, the computational time is reduced up to roughly 60 times compared to the model which is based on shallow water equations. Increasing frequency and intensity of flooding in urban areas have led to serious damage in urban areas. One of the major challenges in urban flood analysis is the two dimensional simulation of surface runoff caused by surcharged flows from urban drainage systems. Thus, development of an urban flood simulation model, which can rout the water flow on complex topography of urban catchments and determine flooded areas with acceptable computational time and accuracy is very important. In this study, a flood simulation model based on cellular automata approach is developed to reduce time and computational effort in compare with other 2D conventional hydraulic models. The developed model performance is compared with HEC-RAS, shallow water equation and TUFLOW models which simulate the water movement using conventional numerical schemes. Also the model’s stability is assessed by considering different time step and mesh size. The obtained results show that the proposed model, using topographic and surface roughness data as inputs, can simulate water movement with acceptable accuracy one- and two-dimensionally. In addition, the computational time is reduced up to roughly 60 times compared to the model which is based on shallow water equations. Increasing frequency and intensity of flooding in urban areas have led to serious damage in urban areas. One of the major challenges in urban flood analysis is the two dimensional simulation of surface runoff caused by surcharged flows from urban drainage systems. Thus, development of an urban flood simulation model, which can rout the water flow on complex topography of urban catchments and determine flooded areas with acceptable computational time and accuracy is very important. In this study, a flood simulation model based on cellular automata approach is developed to reduce time and computational effort in compare with other 2D conventional hydraulic models. The developed model performance is compared with HEC-RAS, shallow water equation and TUFLOW models which simulate the water movement using conventional numerical schemes. Also the model’s stability is assessed by considering different time step and mesh size. The obtained results show that the proposed model, using topographic and surface roughness data as inputs, can simulate water movement with acceptable accuracy one- and two-dimensionally. In addition, the computational time is reduced up to roughly 60 times compared to the model which is based on shallow water equations.
    Keywords: Urban Flood, Cellular Automata, Hydraulic Modeling, Surface runoff
  • Evaluation of Hydraulic Performance of Ilam Gas Refinery fire-fighting water network (middle ring)
    Jafar Mamizadeh *, Ali Kamandi Pages 90-105
    Evaluation of Hydraulic Performance of Ilam Gas Refinery fire-fighting water network (middle ring) Abstracts Hydraulic simulation of conveyance lines and fire-fighting distribution networks are considered appropriate tools for their assessment. In this research, Ilam gas refinery network (middle ring) was evaluated using field studies and hydraulic simulation software. The fire-fighting water network is divided into upper, middle and bottom rings. Each rings of the network are responsible for the one part of the refinery area. Hydraulic simulation of the water conveyance pipeline from the main reservoir to the middle ring reservoir were carried out in four modes of gate valve operation. Different fire scenarios were carried out to investigate the operation of fire-fighting network. The most critical scenario was the fires in floating roof tanks; with a flow rate of 1375 m3/h. Sensitivity analysis was performed on changes in the roughness coefficient of pipes and the required flow rate in the network. With an increase of roughness by 20%, the average pressure in the middle ring decreased by as much as 3.5%. In the case of increasing the required flow, the pumping pressure and deluge valve pressure drop by 3.2 and 12.2%, respectively. Field investigation showed that 20 percent of hydrants have problems and leaks. Field inspection of the cooling system operation of floating roof tanks was carried out with the activation of one and two electric pumps. The measured pressure gauge at the pumping station with one and two pumps is 11 and 12 bars, and these pressures are higher than 10 bar allowable pressure. The field inspection of tanks foam system was performed with the one of a diesel pump. The pressure gauge showed 12 bars at the middle-pumping station, which could cause a failure of the ring equipment. Keywords: Fire-fighting, hydraulic simulation, WaterGEMS, Ilam gas refinery Introduction Fire water distribution networks consist of interconnected sets of reservoirs, pipes, pumps, hydrants, hose reels and valves that are responsible for the transfer and distribution of water with suitable pressure and quality for firefighting demands. Hydraulic simulation of conveyance lines and fire-fighting distribution networks are considered appropriate tools for their assessment. In this research, Ilam gas refinery fire water network (middle ring) was evaluated using field studies and hydraulic simulation software. Methodology Ilam gas refinery fire water network is divided into upper, middle and bottom rings. Each rings of the network are responsible for the one part of the refinery area. The maximum and minimum diameter of the distribution pipes is 14 inches and 6 inches, respectively. Polyethylene pipes have a working pressure of 16 bars. The maximum allowable velocity in the pipes is 3.5 m /s. At the refinery site, several centrifugal pumps have been used to supply pressure during firefighting, maintaining a pressure of 10 bar in the main ring. The total number of hydrants, shut-off valves and hose reels are 170, 147 and 76, respectively. WaterGEMS hydraulic software was used to simulate Ilam gas refinery fire water network. Results and discussion Different fire scenarios were carried out to investigate the operation of fire-fighting network. The most critical scenario was the fires in floating roof tanks; with a flow rate of 1375 m3/h. Hydraulic simulation of the water conveyance pipeline from the main reservoir to the middle ring reservoir were carried out in four modes of gate valve operation. Field investigation showed that 20 percent of hydrants have problems and leaks. Field inspection of the cooling system operation of floating roof tanks was carried out with the activation of one and two electric pumps. The measured pressure gauge at the pumping station with one and two pumps is 11 and 12 bars, and these pressures are higher than 10 bar allowable pressure. The field inspection of tanks foam system was performed with the one of a diesel pump. The pressure gauge showed 12 bars at the middle-pumping station, which could cause a failure of the ring equipment. Conclusion In this research, the middle ring of the fire water network of Ilam gas refinery was tested and evaluated using the WaterGEMS hydraulic simulation software. Different scenarios related to this ring, which included the simultaneous operation of several hydrants and deluge valve in different areas, were simulated. Sensitivity analysis was performed on changes in the roughness coefficient of pipes and the required flow rate in the network. With an increase of roughness by 20%, the average pressure in the middle ring decreased by as much as 3.5%. In the case of increasing the required flow, the pumping pressure and deluge valve pressure drop by 3.2 and 12.2%, respectively. The results of the study indicate the proper operation of the firefighting water network, but in some cases the pressure generated at the pumping station is higher than the recommended values in the design, which in the long period could result in inappropriate performance.
    Keywords: Fire-fighting, Ilam gas refinery, Hydraulic simulation, WaterGEMS
  • Evaluation of Hydraulic and Stability Behavior of Homogeneous Earth Dam with Combined Drain
    Azam Kouhpeyma, Fouad Kilanehei *, Mahmoud Hassanlourad, Reza Ziaee Moayad Pages 105-115
    Introduction Different types of drainage systems are used for seepage control through earth dams; including: horizontal toe drain, triangular toe drain, chimney drain and combined toe drain. Earth dams are constructed by soil compaction, so horizontal permeability is more than vertical permeability. As a result, hydraulic performance of chimney drain is better than triangular toe drain and operation of triangular toe drain is more suitable than horizontal toe drain. On the other hand, triangular toe drain can be repaired due to the more accessible position, if necessary, and is easier to implement than chimney drain. In this research, a combined drain, as a replacement for triangular toe drain is introduced, and its hydraulic performance is studied and compared with triangular toe drain. In order to achieve this goal, first, the hydraulic efficiency of the combined drain is investigated through physical modeling. After assuring the positive performance of combined drain and acceptable comparing of numerical and physical modeling results, sensitivity analyses of seepage and stability were performed numerically. For this, the height of triangular toe drain was decreased from 20 to 50%, and a part of the saved material was attached to triangular toe drain as horizontal toe drain. This kind of drain called combined drain. Methodology In this study, first, hydraulic performance of 3 physical models with different drainage system (without drain, with triangular toe drain, and with combined drain) is studied. Models were constructed in a box with 11 piezometers and 2 spillways in upstream and downstream which are used to keep the water level fixed in reservoirs. Height, length and width of this box are 1m, 1.1m, and 0.15m, respectively. Height of physical models, considering the dimensional constraints of box considered 49 cm. The slopes angles were kept about 45 degrees and the crest width was dictated 21 cm. The height of triangular toe drain, considering Creager’s recommendation was choosed 17 cm. In models with combined toe drain, height of triangular part, considering 15% reduction, was assumed to be 14.5 cm and length and thickness of the horizontal part of combined drain were held to be 11.5 and 5 cm respectively. Upstream and downstream water level were set as 47 and 4 cm for all models. Piezometric water level as a representative of phereatic surface, and volumetric flux were recorded from physical models. Then numerical models were run using Geo-studio software. Hydraulic performance comparison between these two physical and numerical analyses illustrated acceptable agreement; In the following, additional analyses were performed just numerically in order to assurance the adequacy of combined drain. The size and characteristics of numerical models were assumed based on real earth dams characteristics. Seepage analyses were performed for both steady state and rapid drawdown conditions, then stability analyses were done for downstream slope (end of construction, steady flow condition and quasi-static condition) and upstream slope (drawdown condition) for these mpdels. Results and discussion Comparison between models having triangular toe drain and combined toe drain, in whih half of the remaining material from toe triangular drain height reduction were horizontally atached to toe drain, showed an increase in cover length of downstream on phreatic line, and also noticeable rise in amount of discharged water; so in the next step, models having combined toe drain, with the same hydraulic performance as models with triangular toe drain were compared. Also, stability performance of these two models were evaluated. Stability analyses of models, showed ignorable difference in factors of safety, due to little share of drain area in slip surface in which causes slight change in shear strength, and also, phreatic surface dropping down in which causes an increase in dry area of earth dam downstream and induces an increase in unit weight of soil and subsequently, expansion of slope stability. Conclusion. The process described in the previous parts, approved proper performance of combined drain when it is used as a replacement for triangular toe drain. It was revealed that when a triangular toe drain substitute with combined drain, it will improve the hydraulic performance of the earth dam and will also result in a noicable reduction in drain material usage in which is more expensive than body material. In addition, this replacement will have a negligible effect on the static and quasi-static stability of the reservoir slopes. Therefore, the proposed drainage system’s adequacy is confirmed as a suitable alternative for triangular toe drain in homogeneous soil dams. Results indicated 11 to 157% increase in cover length on downstream phreatic line and 25 to 50% reduction in drain material compared with triangular toe drain, in models which half of the saved drain material, was used as horizontal toe drain. On the other hand, using combined drain with the same hydraulic performance instead of triangular toe drain results in 17 to 60% decrease in volume of drain material.
    Keywords: Homogeneous earth dam, Combined drain, Seepage analysis, Stability Analysis, Physical, Numerical modeling
  • The experimental study of the river sand and gravel mining on the scouring pattern around pier group
    Mahdi Majedi Asl *, Rasoul Daneshfaraz, Saeideh Valizadeh Pages 115-130
    Sand mining, especially from places with lower potential, impacts on the hydraulically and sedimentary properties around the bridge piers. The creation of the turbulence causes to the negative effects on the scouring depth and width around the piers. In the present study, the consequences of the mining material, the hydraulical, and sedimentary parameters on the scouring patterns of the piers group were investigated. In order to investigate the scouring of a bridge pier group, 22 experiments were carried out in a rectangular canal with a dimensions of 13 m length, 1.2 m width and 0.8 m depth. The experimental facility is housed at the Hydraulic Lab of Maragheh University. Two false glass floors were installed upstream and downstream at a distance of 4.25 m relative to each other and with a height of 22 cm in the middle of the canal. Sandy movable bed with a height of 22 cm was placed between the aprons. Two pier groups were located upstream and downstream of the bed a specified distance from the aprons. The pier groups with the same arrangement (three consecutive piers in the direction of flow and at the center of the canal's width) were located with center-to-center distances of 21 cm. To eliminate the effect of the canal wall on local scour, the ratio of the pier center-canal wall distance to the pier diameter was greater than 6.25 (Raudkivi and Ettema (1983)). Consequently, piers of diameter of 9 cm were used. To prevent the formation of a ripple, the average diameter of the bed particles should be greater than 0.7 mm and the ratio of the pier diameter to the average particle should exceed 20-25 (Raudkivi and Ettema (1983)). Therefore, the experiments were tested in two different beds, grading ꞌAꞌ with =0.78 mm and grading ꞌBꞌ with =1.7 mm. In order to investigate the effect of the mining pit hole on scouring rate, the mining was done between the upstream and downstream pier groups. The results showed that granulation with coarse particles (B) had lower scour depth than substrate with fine grain size (A). So that the maximum scour depth for B aggregate for Froud number equal to 0.5 and 0.25, was respectively, 14.14 and 47.58 percent less than A. By mining of bed from the downstream and upstream of the group piers, the scouring depth has been increased and reduces respectively. In the Froude number of 0.5 with the mining of materials from the upstream of the groups in the grain size A, the scour depth was 12 to 10.9 cm. However, taking off the bottom of the bases in the same Froude and grading number increased the maximum scour depth from 15 to 15.6 cm. Also, the maximum scour depth in a discharge of 15 liters per second was less for B, compared with A, for gravel A, in Froud number of 0.25 and 0.5 respectively, 44.87% at the fourth base and 61.86% at the first pier, less observation. Although the ratio values in the Froude number of 0.25 for grain size A in the downstream bed is approximately 4 times the grain size of B. Also, the lowest ratio in the Froude number of 0.25 is for the B model with the non-pit hole mining material, while the grain size A with the downstream bed is one of the most scouring models in this Froude number. The phenomenon of scouring in addition to depth dimension, can be studied along the transverse and longitudinal direction. Scouring area is another dimension of the scouring phenomenon that can be affected by parameters. Therefore, the extent of scour area changes in two parts of the scour pattern and bed topography were investigated. In this research, nonlinear regression method is used to predict scour depth around bridges. The relationship between experimental data and empirical of other researchers has been verified using experimental data of this study. In the present study, the scour area around the pier group, along the flow direction for two bed and pit hole was investigated. The effect of this impression on the pattern and depth of scouring showed that the mining of materials from the upstream of the pier groups led to a decrease and this withdrawal from the downstream, increased the depth and extent of scouring. Therefore, it was observed that the pier groups were more sensitive to the mining of materials from their downstream, and it would be better to take this impression upstream of the pier group. Increasing the number of Froude from 0.25 to 0.5 has increased the depth of scouring around the pier group. This increase is higher in larger discharges. Increasing the Froude number in mining of material mode will affect the downstream bed more than the no-pit. So, increasing the Froud number in the bed with the pit hole compared with the non-pit hole bed increases the scour maximum for A, 33% and for B, 73.5%.
    Keywords: Scouring pattern, Pier group, bedding grading, material mining
  • Quasi 2D analysis of Column separation and Bubbles Growth in Water Hammer
    Seyedeh Maryam Mousavifard *, Reza Roohi Pages 125-135
    Numerical Investigation of Column separation and Bubbles Growth in Water Hammer Maryam Mousavifard‎, Assistant Professor, Department of Civil Engineering‎, Faculty of engineering‎, Fasa University, Fasa, Iran Reza Roohi‎, Assistant Professor, Department of Mechanical Engineering‎, Faculty of engineering‎, Fasa University, Fasa, Iran Introduction In modern hydraulic systems, when a sudden change occurs in fluid velocity because of any reasons (sudden pump stroke, valve closure, etc.), it will be followed by intense pressure fluctuations in the system, which is referred to water hemmer. If the fluctuations decrease to less than the vapor pressure of the fluid, the separation column will occur. In general, two cases can be distinguished: either the pressure drops below the saturation pressure but keeps above the vapor pressure, or the pressure drops to the vapor pressure of the liquid. In the former case, gaseous cavitation takes place, characterized by the presence of a large number of gas nuclei. When the pressure drops suddenly, a significant gas release may occur. In the latter case, vaporous cavitation takes place, and when the fluid pressure drops to its vapor pressure, a sudden growth of the nuclei containing vapor occurs. In general, there are two basic assumptions to describe the phenomenon of cavitation: discrete and distributed cavitation. In discrete cavitation, the vapor or gas cavities create discontinuity in fluid. In this case, it is assumed that the vapor and gas cavities occur at computational nodes, when the pressure reaches less than the vapor pressure of the fluid or the saturation pressure. In distributed cavitation, the two phases of the liquid and the vapor (or the gas) are simultaneously solved, and the vapor (or gas) cavities are continuously exist all over the fluid. Methodology In this paper, the column separation in pressurized pipes affected by water hammer is numerically investigated using one-dimensional and quasi-two-dimensional models of gas cavity. A one-dimensional model is modeled based on the method of characteristics, and the energy dissipation is simulated using the summation of the Brunone unsteady friction and quasi-steady friction. In the proposed quasi-two-dimensional model, the characteristic equations along the pipeline axis and the finite difference equations along the pipe radius are used to simulate water hammer, and then the governing equations of discrete gas cavity model is coupled with the primary model, and the five-layer turbulence model was also used to simulate the energy dissipation. It should be noted that, in the quasi two dimensional model of separation column, like the one-dimensional model, the velocity on the upstream and downstream of each computing node will not be equal. Free gas distribution throughout liquid in a homogeneous mix in a pipeline yields a wave propagation velocity that is strongly pressure dependent. Results and Discussion After verifying the developed models by experimental data, the total shear stress is studied in some initial cycles of water hammer. In the second part of the paper, the dynamics of bubble growth and the process of temperature and pressure variation within the bubbles are also analyzed using the Rayleigh-Plesset equation. The growth of bubbles in the fluid is a function of a variety of variables such as applied pressure, fluid surface tension, evaporation pressure in fluid temperature and viscosity. Conclusion - the quasi-two-dimensional model has been more successful in calculating energy depreciation, especially in the final cycles of water hammer. - Regarding the head oscillation shape, it can be evaluated that the quasi 2D DGCM improved the energy losses reproduction, and reproduces the experimental spikes successfully even in final cycles of experimental runs. - The 1D model of DGCM reproduce the first oscillations of the experimental data successfully, but in final cycles, does not predict the shape of head oscillations successfully and does not stay in phase with experimental data. - According to the shear stress diagrams it can be concluded that in high pressure pulses, the total shear stress is negative and it is positive in low pressure pulses. - The difference between the minimum and maximum radius is about 0.5 μm. Considering the average radius of the bubbles and the relationship between the radius of the bubbles and the gas phase volume, the 85 to 125% increase in the volume of the gas phase in the fluid during the periodic pressure fluctuations process, is visible. - It should be noted that in spite of the fact that the maximum pressure inside the bubbles (the driving force for the growth of bubbles) is greater than the external pressure, the high dependence of the internal gas pressure on the radius of the bubbles and the dynamic behavior of the system, lead to periodic changes. In other words, the strong growth of the resistive force by reducing the radius of the bubbles prevents significant contraction in them, and again, by reducing the pressure head in the fluid, the growth of the bubbles will be renewed to reach the initial radius. Keywords: Water hammer; Column separation; unsteady friction; quasi two Dimensional model; shear stress; Rayleigh Plesset equation
    Keywords: water hammer, Column separation, Unsteady friction, quasi two dimensional model, Shear Stress, Rayleigh- Plesset equation