1388
4
3
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85
0
بررسی عددی روند تغییرات غلظت هوا در جریان های عبوری از روی تنداب ها
Numerical Investigation of Air Detrainment Process in Chute Flows
http://jhyd.iha.ir/article_85525.html
10.30482/jhyd.2009.85525
0
1
One of the most important factors in designing spillways is to consider sufficient discharge capacity.Possible creation of negative pressure over spillway during high flood conditions can be a potential foroccurrence of cavitation damage. Flow aeration might be one of the best ways to prevent thisphenomenon. Realizing the air detrainment process along the chutes is a key problem in designingaerators. Although experiments on hydraulic models have their own advantages, but these methods areexpensive and time consuming. In this study the CFD code FLOW-3D® has been used to determine thespillway flow air concentration in case of aeration by means of deflectors. Comparison of obtainedresults with the Kramer's experimental results shows good agreement. It has been realized that theflow bottom air concentration downstream of deflectors reduces exponentially.
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17
آروین
بهرامی
A.
Bahrami
ایران
غلامعباس
بارانی
golamabbas
barani
دانشگاه شهید باهنر کرمان
ایران
gab@mail.uk.ac.ir
0
بکارگیری الگوریتم ژنتیک در مساله معکوس تخمین ضرایب زبری لوله ها در شبکه های تحت فشار
Application of Genetic Algorithm for Determining the Existent Friction Coefficients in the Real-life Pipe Networks as an Inverse Problem
http://jhyd.iha.ir/article_85526.html
10.30482/jhyd.2009.85526
0
1
An integrated approach for determining the existent friction coefficients in water networks isproposed. As pressurized systems age, the carrying capacity of network decreases because the internalroughness increases with the aging of pipes. This can lead to loss of satisfactory performance anduneconomic operation. Therefore, rehabilitation of an existing network becomes very importantproblem in water industry. Determining the real physical characteristics of pipes for network analysisis a regular component of the rehabilitation process. Pipe friction coefficients cannot be determinedexplicitly by direct measurement, they are determined implicitly, as an inverse problem, frommeasured model outputs (pressures). Values of friction coefficients are determined in a way that theyshould yield a reasonable match between measured and predicated pressures in the network. Oneproblem associated with the Re-calibration of real-life pipe networks is the lack of field measurements,which can sometimes, lead to the formulation of an ill-posed inverse problem. In this study certainmethods have been utilized to tackle this problem. The hydraulic analysis of steady and quasi-steadyflow and optimization process are combined to develop a program. By selecting a proper optimizationmethod (Genetic Algorithm) the inverse model was developed and verified successfully in a casestudy.
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35
مریم
شهبازی
M.
Shahbazi
ایران
جمال
محمد ولی سامانی
J.
M. V. Samani
استاد گروه سازههای آبی، دانشکده کشاورزی، دانشگاه تربیت مدرس
ایران
samani_j@modares.ac.ir
0
شبیه سازی عددی الگوی جریان در اطراف صفحات مستغرق در مقابل دهانه آبگیر در قوس 180 به منظور تعیین زاویه و ارتفاع بهینه صفحات
Numerical Simulation of Submerged Vanes at 180° Bend with Intake in order to Identify the Optimum Vane’s Angle and Height
http://jhyd.iha.ir/article_85527.html
10.30482/jhyd.2009.85527
0
1
Submerged vanes are plane structures placed on river bed with an angle to the approach flow whichcause secondary flow. They are used to reduce sediment entrainment to water intakes structures. Thevane’s geometric parameters affect the flow pattern around the vanes. Numerical solution of the threedimensionalReynolds-Averaged Navier-Stokes equations for turbulent flows around submerged vanesplaced in front of the intake in curved channel with 180° bend using the Fluent software in order toidentify the optimum vane’s angle and height and the last vane position is the aim of this paper. Theresults of numerical model are compared with available experimental data.Investigations show that the optimum angle of attack for the first vane is 20° to approach flow and theoptimum ratio of the vane height to the flow depth is 36%. Also the last vane position just off thedownstream corner of the intake is recommended.
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52
معصومه
رستم آبادی
M.
Rostamabadi
ایران
rostamimass@yahoo.com
سید علی اکبر
صالحی نیشابوری
S.A.A.
Salehi Neyshabouri
ایران
salehi@modares.ac.ir
حسین
منتصری
H.
Montaseri
ایران
hmontaseri@gmail.com
0
مقایسه جریان در مدل فیزیکی یک بازه رودخانه ای با سه مدل ریاضی برای دو گزینه ساماندهی
Comparison of Flow Characteristics in a Physical Model with Three Numerical Models in a River Reach, under two Different Training Schemes
http://jhyd.iha.ir/article_85528.html
10.30482/jhyd.2009.85528
0
1
Application of numerical models in river engineering projects is unavoidable. However, the reliabilityof model, minimum requirement for field data, and fewer computational processes are of majorconcern. The main purpose of the present study was to test the reliability of some well-knownnumerical models in the simulation of flow characteristics in different river planforms. Comparisonwere made between the flow characteristics in a river physical model and the simulation results fromthree numerical models, under two different river training schemes, with identical initial and boundaryconditions.In this study, a reach of the Nazloo River in Urmia, Iran, was selected. A fixed-bed physical model ofthe River Reach (1200 m long, with horizontal scale of 1:100 and vertical scale of 1:20, and with theNazloo cross bridge included within the reach) was constructed, calibrated and verified. Two trainingschemes were planned, using longitudinal and transversal structures, i.e, levees and groynes. Flowparameters (such as,: depth and point velocity) were measured for four different flows. Three rivermodels: 1D model HEC-RAS, Quasi-2D model BRI-STARS, and 2D model FAST-2D were selected.Six flow parameters (i.e. river flow capacity, water surface elevation, mean flow depth, mean velocity,mean bed shear stress and Froude number) were compared between the physical model and the threenumerical models. Four different flow conditions were examined, and the results were compared inthree sub-reaches along the river reach (from downstream to upstream of the bridge).The averaged predictive errors from these three models were determined for corresponding flowparameters. The HEC-RAS, FAST-2D, and BRI-STARS models are considered to be the best fittedmodels with the true physical model, respectively. Simulation results from the HEC-RAS model arewell adapted to the river flows confined between the two-sided levees, where the geometry of the riverreach is more uniformly defined, and in minor flood flows. The prediction from the FAST-2D modelis superior along the river reach with groynes involved, particularly in higher flow levels. Theapplication of each of the three models is recommended in river projects subject to the inclusion of theorder of certainties provided by the present study.
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68
لیلا
جلیلی
L.
Jalili
ایران
مهدی
یاسی
Mehdi
Yasi
دانشیار مهندسی رودخانه، گروه مهندسی آب دانشگاه ارومیه
ایران
m.yasi@urmia.ac.ir
0
کالیبره سازی مدل تحلیل هیدرولیکی شبکه های توزیع آب با در نظر گرفتن انواع متغیرهای تنظیم و شرایط مصرف
Calibration of Water Distribution Hydraulic Models Considering Different Decision Variables and Consumption Scenarios
http://jhyd.iha.ir/article_85529.html
10.30482/jhyd.2009.85529
0
1
In recent years, hydraulic models are widely used to simulate hydraulic performance of waterdistribution systems. They play a significant role in evaluation and operational management of thesesystems. Calibration is necessary for improvement of model function and reduction of theuncertainties during different consumption scenarios in the system. At the moment just a fewcommercial models are capable of calibration calculation besides the hydraulic performanceevaluation. However, the popular and freely available model, EPANET can not be calibrated. In thispaper, an optimization procedure is proposed using Genetic Algorithm (GA) for calibration of thehydraulic simulator. For this problem, the pipe roughness (Hazen Williams) coefficients, nodaldemands and pipe diameters are considered as decision variables of the optimization problem. Theprocedure is implemented for four different consumption scenarios: normal, minimum, maximum andfire flow. Finally, to evaluate the proposed methodology, a test network at different consumptionscenarios is calibrated and the results are compared. Comparison of the results shows that the bestresult with minimum error has been obtained when the fire consumption with considering bothvariables of Hazen-William coefficient and nodal demand was selected.
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مسعود
تابش
M.
Tabesh
دانشگاه تهران - گروه عمران
ایران
mtabesh@ut.ac.ir
مهدی
جاماسب
M.
Jamasb
ایران
رامتین
معینی
R.
Moeini
ایران
r.moeini@eng.ui.ac.ir