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109
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بررسی آب شستگی در اطراف تکیه گاه پل ها د رحضور لایه سپری
Armored Layer Bed Effect on Local Scouring Around Bridge Abutment
http://jhyd.iha.ir/article_85415.html
10.30482/jhyd.2010.85415
0
1
In this study the effects of armored-bed layer on local scouring around semi-circular and semiellipticalabutments have been studied based on model experimentation. The main objective of thisresearch includes the effect of armor layer on mechanism of clear-water scouring around bridgeabutments. Experiments were performed under different conditions such as bed shear velocities, flowdepths, dimension and shape of abutments, as well as grain size of the bed and armor layer materials ina glass-wall channel of 6.5 m length, 0.3 m width and 0.3 m height. Two types of abutments, semicircularand semi-elliptical with b/l=3 and 2 respectively were used. Results show that by increasingthe bed material diameter for a constant armor layer, maximum scouring depth (dsa) increases and byincreasing the grain size of the armor layer for a constant bed layer, dsa decreases. For a given armorlayer thickness, by increasing the grain size of the bed layer, dsa increases. While small bed particlesare under the protective effect of armor layer, increasing the water velocity increases the secondaryarmor layer depth provided that the armor layer itself is not influenced by the flow. The maximumscour depth for semi-elliptical abutment is less than that of semi-circular abutment.
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19
مهرنوش
ماهرانی
M.
Maherani
ایران
عبدالرضا
کبیری سامانی
Abdorreza
Kabiri-Samani
دانشیار، دانشکده مهندسی عمران، دانشگاه صنعتی اصفهان
ایران
akabiri@cc.iut.ac.ir
حسین
افضلی مهر
H.
Afzalimehr
ایران
hafzali@iust.ac.ir
0
بررسی آزمایشگاهی تاثیر قرارگیری سری پره های مستغرق در بالادست پایه استوانه ای در کاهش آب شستگی
Experimental Assessment of Submerged Vanes Effect on Scour Reduction Located on the Upstream Face of Cylindrical Pier
http://jhyd.iha.ir/article_85416.html
10.30482/jhyd.2010.85416
0
1
Scouring is one of the destructive factors in the hydraulic structures such as bridges. It occurs mainlyduring flood events. To find the most effective countermeasure to protect water structures againstscouring phenomena, extensive investigations have been performed. One of such methods is to usesubmerged series of vanes which is not fully investigated yet. In this study, two series of submergedvanes were used either separately or attached to the upstream face of bridge pier and arrangedsymmetrically on different positions and angles of attack to control scour at cylindrical pier underclear water condition. The results showed that the highest reduction in scour depth occurs as the vanesseries stands closer to the pier. Under the best condition, scour depth was reduced by 80.9 percent.
21
35
سمیرا
رضاپوریان قهفرخی
S.
Rezpourian Ghahfarrokhi
ایران
palmy458@gmail.com
بهزاد
قربانی
B.
Ghorbani
دانشیار گروه مهندسی آب، دانشگاه شهرکرد
ایران
behg1955@yahoo.com
0
تاثیر طول پوشش بستر بر آب شستگی موضعی پایین دست در جت های افقی
Effect of Bed Protection Length on Local Scour Downstream of Horizontal Jets
http://jhyd.iha.ir/article_85417.html
10.30482/jhyd.2010.85417
0
1
Local scour occurs due to interactions between water current, erodible bed and hydraulic structureswhich can endanger performance and stability of these structures. To control this phenomenondownstream of structures such as control gates, various engineering measures such as aprons and riprapprotections have been applied so far. However, investigation on the effect of lengths of thesemeasures requires further studies which are dealt with in the current experimental research. For thispurpose, scour profile due to a horizontal jet issued from a sluice gate was initially measured the(without protection) under different hydraulic conditions. The same tests were then repeated separatelyfor the cases of application of aprons and rip-rap protections to achieve an insight about their effectson the maximum scour depth. Results showed that increasing relative length of aprons (L=a > 1) andrip-rap protections (L=R > 2), decreased the maximum scour depth considerably so that for L=a > 27 andL=R > 7, it decreases up to 100 percent. On this basis, a properly designed and constructed rip-rapprotection (L=R > 2), is more effective on decreasing maximum local scour depth than the apronmeasure. In this paper, suitable empirical relationships (in non-dimensional form) for estimation ofmaximum scour depths (considering lengths of the apron and rip-rap protections) are proposed. Acomparison of the results of the proposed relationships with those of the previous researches showsthat most of the data are within acceptable (±20%) error interval.
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49
علی
مهبودی
A.
Mehboudi
ایران
alimehboudi.ce@gmail.com
جلال
عطاری
J.
Attari
ایران
مجتبی
صانعی
M.
Saneie
ایران
drsaneie@gmail.com
محمدرضا
مجدزاده طباطبایی
M.R.
M. Tabatabai
ایران
mrmtabatabai@yahoo.com
0
مطالعه توزیع تنش برشی جداره در جریان یکنواخت کانال با استفاده از ابزار دقیق و شبیه سازی عددی
Investigation of Wall Shear Stress Distribution in Open Channel Uniform Flow using an Accurate Instrument and Numerical Simulation
http://jhyd.iha.ir/article_85418.html
10.30482/jhyd.2010.85418
0
1
With the aim of investigating the distribution of wall shear stress in an open channel with a rectangularcross section and a smooth bed, an accurate needle type probe has been developed and afterverification, it has been used for shear stress measurement in various cases of open channel uniformflows. In this instrument, capacitive type pressure transducers with 0.1 Pascal accuracy and 100Hzsampling rate were used to measure pressure fluctuations. Measured bed shear stresses are comparedwith the result of available analytical models and CFD simulations using FLUENT code forinstrument verification. Variations of the measured local bed shear stresses at channel centerline withrespect to channel aspect ratios, mean bed shear stresses and the lateral distribution of local bed shearstresses compare favorably with the previous experimental and analytical results and with the resultsof the present numerical simulations. Experimental measurements and numerical simulations showthat the secondary currents affect the distribution of side wall shear stress more than the bed shearstress. Because of the presence of the alternate low-high velocity zones at the near bed region, thelateral distribution of the bed shear stress exhibits an oscillatory pattern.
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70
اکبر
صفرزاده گندشمین
A.
Safarzadeh Gendeshmin
ایران
سیدعلی اکبر
صالحی نیشابوری
S.A.A.
Salehi Neyshabouri
ایران
امیررضا
زراتی
A.R.
Zarrati
ایران
zarrati@aut.ac.ir
مسعود
قدسیان
M.
Ghodsian
ایران
ghods@modares.ac.ir
0
واسنجی چندمعیاره خطوط لوله برای جریان های گذرا
Multi Criteria Calibration of Pipelines under Unsteady Flows
http://jhyd.iha.ir/article_85419.html
10.30482/jhyd.2010.85419
0
1
Partial differential equations of continuity and momentum govern the transient flows in pressurizedpipes. These equations are numerically analyzed using the method of characteristics that consists ofsome important uncertainties such as friction loss modeling and wave speed. This work introduces acalibration methodology to estimate precisely the uncertain parameters and, consequently, thenumerical modeling results. For this purpose, a transient state is generated by closing the downstreamend valve. A numerical model for transient analysis in the pipe is also developed. In that model, fourcorrection coefficients are considered to be calibrated including; pipe roughness, local and convectiveaccelerations in the unsteady friction loss model and wave speed. Afterward, a non linearprogramming is developed in which the correction coefficients are decision variables. The objectivefunction is defined as the summation of squares of differences of the observed and calculatedpressures at the valve location. The problem is then solved using a simple genetic algorithm, and theuncertainties are finally calibrated to the best conditions. The capability of the method is investigatedby solving a well-known experimental pipeline. The approach is found easy to use and results aresatisfactory.
71
80
علی
حقیقی
A.
Haghighi
استادیار گروه عمران، دانشکده مهندسی، دانشگاه شهید چمران اهواز
ایران
a.haghighi@scu.ac.ir
0
برآورد عمق آب در لبه آبشار کانال های منشوری با جریان زیربحرانی در بالادست
Estimation of Brink Depth for Prismatic Channels in Sub- critical Approach Flow
http://jhyd.iha.ir/article_85421.html
10.30482/jhyd.2010.85421
0
1
To measure flow discharge and study erosion at the brink of free overfalls, computation of End DepthRelationship (EDR) is required in civil engineering practice. Based on the energy equation, a methodis presented to estimate EDR in channels for different cross sections. Using available experimental andtheoretical results of other studies, the proposed relationships were examined. This method yieldsgood results for rectangular, triangular, parabolic, inverted semicircular and inverted triangularchannels but fairly agrees with the experimental results in the case of trapezoidal and circular crosssections.
81
89
سیدوحید
نبوی
S.V.
Nabavi
ایران
nabavi@cv.iut.ac.ir
محمد کریم
بیرامی
M.K.
Beirami
ایران
beirami@cc.iut.ac.ir
0
مطالعه آزمایشگاهی اثر شعاع انحنا بر جریان ثانویه در قوس 90 درجه در شرایط بستر تعادل یافته
Experimental Investigation on the Effect of Curvature of Bend on Secondary Flow in 90 Degree Bend under Equilibrium Bed Condition
http://jhyd.iha.ir/article_85422.html
10.30482/jhyd.2010.85422
0
1
Flow pattern in the bend channels is different from that in the straight channels. Flow is affected byboth pressure gradient and centrifugal forces in the bend of rivers and their interaction leads to formsecondary flow. In the channel bend, radius of curvatures of the bend cause changes in the formationof secondary flow and consequently the flow pattern in the bend. This paper presents variation of flowthrough measurement of three dimensional velocities of the flow in the layers and different sections ofa 90 degree bend under equilibrium bed condition. Experiments were conducted in an experimentalchannel with three different radius of curvature, i.e. mild, moderate and sharp. Vecterino, a threedimensionalvelocity meter, is used to measure the three dimensional velocity of the flow. Formationand changes of secondary flow pattern in the three bends with different radius of curvature isdiscussed. The results indicate that power of secondary flow and vorticity in the second half of thebend increase with decrease in the radius of curvature of the bend. Also, a flow called secondsecondary flow forms near the outer bank and in the opposite direction of the main secondary flow.This flow is evident in the middle sections of first half of bend up to the end of the bend.
91
99
محمد
واقفی
M.
Vaghefi
ایران
vaghefi@pgu.ac.ir
مسعود
قدسیان
M.
Ghodsian
ایران
ghods@modares.ac.ir