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برآورد زمان پیمایش جریان دامنه ای با استفاده از تقریب موج پخشی
Estimation of Travel Time in Overland Flow via Diffusive Wave Approximation
http://jhyd.iha.ir/article_85478.html
10.30482/jhyd.2009.85478
0
1
Different analytical methods such as kinematic wave (KW) and diffusive wave (DW) approximationcan be used to investigate the overland flow mechanism. In this article, for the first time, the results ofthese two methods are compared in calculating the travel time of flow over a rectangular plane.Positions of isochrones and the effect of bed slope on travel time are also investigated. It is elaboratedthat travel time of the rectangular plane in diffusion wave approximation is greater than that of thekinematic wave approximation. For example, by decreasing bed slope from 0.01 to 0.001 the traveltime will increase by 99% in kinematic wave approximation and 130% in diffusive waveapproximation. Also, the relative difference of the two methods will increase by 14%. It is alsodeduced that by decreasing the bed slope, the difference between the two subsequent isochronedistances will become greater in diffusion wave approximation than that of the kinematic waveapproximation. On the other hand, with 10% of relative difference between kinematic and diffusivewaves the criterion of 20 0 K F < 5 would be fulfilled.
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12
سعید
گلیان
S.
Golian
ایران
s.golian@aut.ac.ir
بهرام
ثقفیان
B.
Saghafian
ایران
saghafian@scwmri.ac.ir
محمود
ذاکری نیری
M.
Zakeri Niri
ایران
m.zakeri.w90@gmail.com
0
توسعه مدل ریاضی سیستم کنترل فازی پایین دست در کانال های آبیاری
Development of Downstream Fuzzy Control System for Irrigation Canals
http://jhyd.iha.ir/article_85479.html
10.30482/jhyd.2009.85479
0
1
Limited water resources and poor performance of irrigation networks has attracted the attention ofexperts to improve water delivery management by application of improved control systems. Improvedcontrol systems in irrigation canals, because of complex hydraulic behavior, should be developed andtested using mathematical and hydrodynamic models. Fuzzy theory has been widely and successfullyapplied in several engineering control problems. In this research fuzzy theory has been applied forcontrol of irrigation canals. For the development of fuzzy control system, the ICSS hydrodynamicmodel which could simulate unsteady hydraulic behavior in response of control systems in irrigationcanals is used. The performance of developed mathematical model of fuzzy control system is tested incanal standard no. 2 introduced by ASCE, considering large flow variations. The performance of fuzzycontrol system is evaluated using several indicators such as, maximum absolute error, cumulativeabsolute error, and response time. The figures of flow, depth, and gate opening variations in time areanalyzed as well. The results show that by applying large flow variations, the maximum depthdeviation was 1.9%. The maximum response time for water depth to be stabilized within 1% range oftarget depth was 1.8 minutes. The results indicate that the developed fuzzy control system wassuccessful in downstream control of irrigation canal and could be introduced for practical applications.
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محمد جواد
منعم
M.J.
Monem
عضو هیئت علمی گروه سازه های آبی دانشگاه تربیت مدرس
ایران
monem_mj@modares.ac.ir
محمدصادق
کیاپاشا
M.S.
kiapasha
ایران
0
کنترل جهش هیدرولیکی در مقاطع ذوزنقه ای با استفاده از بلوک های کف
Control of Hydraulic Jump in Trapezoidal Stilling Basin by Basin Blocks
http://jhyd.iha.ir/article_85480.html
10.30482/jhyd.2009.85480
0
1
Over the decades, extensive data have been gathered for the design of stilling basins but most of thesedata are restricted to jumps in rectangular channels. However, geometries different from therectangular such as trapezoidal cross sections are also considered for stilling basins. On the otherhand, unsteadiness of jump and increase in jump length are unwanted changes in the characteristics ofsuch basins. In this study, the effect of basin blocks on the jump characteristics in a stilling basin oftrapezoidal cross section is investigated. Five different block sizes corresponding to Froude numbersof 4, 5.5, 7, 8 and 9 for three different block locations of 0.8d2, d2 and 1.2 d2 from the jump toe werestudied (d2 is the sequent depth). The results show that the installation of a set of basin blocks mayimprove the jump condition and decrease the unsafe transverse waves and vortices. It was also foundthat the basin blocks cause a significant reduction in the sequent depth ratio and jump length, and anincrease of the energy loss in the jump relative to those observed in the jumps occurring in atrapezoidal stilling basin without blocks.
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عاطفه
منصوری
A.
Mansouri
ایران
محمد حسین
امید
Mohammad Hosein
Omid
گروه آبیاری و آبادانی دانشگاه تهران، کرج، ایران
ایران
momid@ut.ac.ir
ایراهیم
امیری
E.
Amiri
ایران
0
محاسبه توزیع فشار بر روی پرتاب کننده جامی
Calculation of Pressure Distribution over Flip Buckets
http://jhyd.iha.ir/article_85481.html
10.30482/jhyd.2009.85481
0
1
Flip buckets are used as terminal structures at the end of chute spillways or bottom outlets. Flow aftera bucket is issued in the form of a jet to a location far from the bucket where it impacts the river bedand forms a plunge pool. Energy of high speed flow is dissipated in the plunge pool and flow entersthe river with a low velocity. Design of buckets and calculation of dynamic pressures over a bucket isusually done by physical model studies or design charts based on field measurements. Physical modelstudies are expensive and modification of the model takes time and is also difficult. Design charts arealso developed based on limited field measurements. In the present study dynamic pressures over flipbuckets are calculated using a numerical model. To simulate the free surface high speed flow overbuckets, FLUENT computer code is employed. The numerical model was verified using existingexperimental data. Free surface location, as well as pressure distribution over buckets were comparedwith measurements and very good agreement was obtained. The effect of Froude number and ratio offlow depth to bucket radius was also investigated. The results of analytical models for pressuredistribution over buckets were also analyzed, discussed and compared with numerical data.
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نازنین
خضری
N.
Khezri
ایران
امیررضا
زراتی
A.R.
Zarrati
ایران
zarrati@aut.ac.ir
فرهاد
گلزاری
F.
Golzari
ایران
0
مدل سازی و تخمین عمر خستگی رایزرهای دریایی در سکوهای ثابت
Modeling and Estimation of Fatigue Damage Accumulation in Marine Risers of Fixed Platforms
http://jhyd.iha.ir/article_85482.html
10.30482/jhyd.2009.85482
0
1
Offshore gas and oil fields are being discovered and exploited nowadays in water depths of more than2000 m. The operation in depths increases the external forces so that the equipments should be moreadvanced and expensive. Fatigue damage accumulation is one of the most important problems aboutmarine structures that are exposed to the alternative loads. Riser is one of these structures. Thesurrounding environment of riser causes alternative stresses and fatigue in riser. To obtaini thesestresses, the analysis of the vortex induced vibration in two direction, in-line and cross flow, isnecessary. The risers are long relative to their cross sections so that the Euler-Bernoulli theory isapplicable for description of the pipe dynamic bending. The flow and riser motion in x direction formsa vortex shedding in front of riser. These vortices cause the drag force in x direction and the lift forcein y direction. These forces are time dependent. The drag force is obtained from Morison’s formula.The lift force excites the vibration in y direction. After obtaining the equation of motion and solving itby using numerical methods such as Galerkin, finite difference and Runga-Kutta fourth order method,the riser deflection in two directions will be obtained and the stress at the outer diameter of riser willbe calculated. The fatigue damage accumulation in the riser can be obtained by using Shigley theoryand Palmgren-Miner rule.
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امیر
مقیسه
A.
Moghiseh
ایران
amirmoghiseh@gmail.com
همایون
ریاحی
H.
Riahi
ایران
عباس
رهی
A.
Rahi
ایران