Effect of Collar on Time Development of Scouring Around Rectangular Bridge Piers
M.
B. Mashahir
author
A.R.
Zarrati
author
E.
Mokallaf Sarband
author
text
article
2008
per
Collars acts as a barrier to the down flow and prevent its direct impingement to the streambed. In thepresent work collars with 3 different lengths (5B, 7B and 9B, B=pier width) and constant width equalto 3B were installed around a rectangular pier with aspect ratio equal to 1:3. Also, collars wereattached at the streambed level and all tests were conducted at the threshold of bed material motionwhere maximum depth of scour hole is expected. Piers aligned with the flow and skewed at 10o and20o to the flow were tested. Long time tests were carried out to study the development of the scourhole around the pier and efficiency of the collar. Based on experiment results with 9B collar, flowcould not penetrate below the upstream edge of the collar after 185 hours. Therefore, scouring at theupstream region of the pier will not occur. In this test maximum depth of scouring occurred at thesides of the collar with 60% reduction of local scouring compared with an unprotected pier. Withskewed pier performance of the collar on reducing the rate of scouring was decreased. Results of theexperiments showed that at skewed piers, after 50 hours depth of scouring reduced about 30%compared with an unprotected pier. In addition the rate of scouring decreased with 9B collar.
Journal of Hydraulics
Iranian Hydraulic Association
2345-4237
3
v.
2
no.
2008
19
11
http://jhyd.iha.ir/article_85463_573934268023eb89f23f8ae2972fb03e.pdf
dx.doi.org/10.30482/jhyd.2008.85463
Development of Optimal Design of Flood Control Systems Model Considering Detention Dams Using Genetic Algorithm
M.H.
Afshar
author
A.
Afshar
author
S.H.
Meraji
author
M.
Ghafari
author
text
article
2008
per
Flood conducting and controlling systems are very huge and the construction and operation of thesesystems are very expensive. Any reduction in the construction cost of these system will lead to a majorsaving. This paper addresses the problem of optimal design of flood controlling systems usingdetention dams and proposes a methodology for the optimal design of these systems usingevolutionary algorithms. The method uses Genetic Algorithm (GA) as a search engine and theTransport Module of the SWMM as the simulator. The simulator is able to analyze the unsteady flowin open channels and the basin of the dam. It is shown that interfacing GA as the optimizer andSWMM as the simulator leads to an efficient optimization tool for the optimal design of floodcontrolling systems. The effectiveness and efficiency of the model is tested against a simple analyticalproblem The applicability of the model for large scale real world problems is verified by solving theflood controlling system of South Pars Project and the results are compared with those proposed by theConsulting Engineers. The results show that proposed optimization model can considerably (about23%) reduce the total costs of flood controlling systems.
Journal of Hydraulics
Iranian Hydraulic Association
2345-4237
3
v.
2
no.
2008
13
26
http://jhyd.iha.ir/article_85464_f204b6a9d0748ea4f9fcd8056269fc3a.pdf
dx.doi.org/10.30482/jhyd.2008.85464
Leak Detection in Pipelines Based on Inverse Transient Modeling and Mixed Integer Nonlinear Programming
H.
Shamloo
دانشگاه خواجه نصیر
author
A.
Haghighi
author
text
article
2008
per
For leak detection in a pipeline, transient flows are generated by closing the end control valve. Thenthe pressure fluctuations are sampled only at the valve location after its full closure. To eliminateundesirable noisy effects and other uncertainties associated with numerical modeling of the valve, anew structure of the method of characteristics (MOC) has been developed independent of the valvetype, the method and the duration of closure with no need to impose initial conditions. Using thepressure samples, transient flow through the pipe can be analyzed backward from the downstream endvalve to the upstream reservoir. In this condition, the calculated reservoir heads will be functions ofleaks parameters containing leaks area as real parameters and the number and location of leaks asinteger parameters. In order to find leaks parameters in a pipe an objective function is defined as thesum of squares of differences of the observed and calculated reservoir heads. The Mixed Integer NonLinear Programming (MINLP) is used to minimize nonlinear objective function and determine theinteger and real parameters of the leak problem. An optimization method based on genetic algorithmhas been developed for this problem. Several examples are solved to show the ability of the presentedmethod. The method was found to be practical, reliable and easy to be used.
Journal of Hydraulics
Iranian Hydraulic Association
2345-4237
3
v.
2
no.
2008
27
42
http://jhyd.iha.ir/article_85465_9ac0e43b5d9ad280c05040191c60df71.pdf
dx.doi.org/10.30482/jhyd.2008.85465
Comparison of 2-D and 1-D Simulations of Water-Hammer Pressure Pulse Damping Using Steady and Unsteady Friction Terms
B.
Firoozabadi
دانشگاه صنعتی شریف دانشکده مکانیک
author
H.
Hamedi Nezhad
author
text
article
2008
per
The condition known as water-hammer problem is in fact, a transient condition which may occur as aresult of the worst-case loadings such as pump failures, valve closure in a pipe line system. In suchcases, a positive pressure wave travels upstream and a negative wave downstream from the point ofinterruption. The pressure in the water hammer can vary in such a way that in some cases, it mayincrease and cause destruction to the hydraulic systems. The experimental evidence of dependence offriction on frequency in oscillating flows induced researchers to propose 1-D models in which thiseffect is taken into account explicitly. In fact, the velocity profiles in unsteady flows show greatergradients, and thus greater shear stresses, than the corresponding values in steady flows. 1D- modelapproaches give rise to an under- estimation of the friction forces.In this work, a 2-D model for unsteady transient flow in a pipeline with a reservoir-pipe-valve systemwas simulated for laminar and turbulent flows. In turbulent flow, the Prandtl mixing length was usedfor turbulence modeling. Results of this simulation were compared with the results obtained from the1-D models with steady and unsteady (Brunone model) friction terms. This simulation shows that theunsteady flow phenomena can be more accurately modeled by means of 2-D models, in which thevelocity profiles in the cross section, is taken into account. However, the 2D model is more timeconsuming than 1D model. Through comparisons with the experimental data, results show thatapplying 2D model can improve the magnitude of the predicted duration of the pressure pulse.
Journal of Hydraulics
Iranian Hydraulic Association
2345-4237
3
v.
2
no.
2008
43
58
http://jhyd.iha.ir/article_85466_608a62830a10658c24c8553b0e13d5fb.pdf
dx.doi.org/10.30482/jhyd.2008.85466
Estimating the Fall Velocity of Sediment Particles Using Artificial Neural Network
S.M.
Sadat-Helbar
author
E.
Amiri-Tokaldany
دانشگاه تهران
author
F.
Darzi
author
text
article
2008
per
The fall velocity of sediment particles is one of the important parameters in the phenomenon ofsediment transport, river bed and bank morphology, reservoir sedimentation and designing settlingbasins of water transport networks. To estimate the sediment fall velocity, many relationships in theliterature have been used by scientists and engineers but they have limitations. In this research, usingan Artificial Neural Network, a model to estimate the sediment fall velocity is introduced. The modelis designed and validated using 115 series of data presented in different researches covering anextensive range of sediment and fluid characteristics. The multi layer perception network with quickback propagation learning scheme is used to estimate the nonlinear mapping between input data, i.e.independent variables, and the output of the network, i.e. dependent variable. This nonlinear mappingis used to estimate the fall velocity. To evaluate prediction accuracy of the model, predictions of thedesigned network are compared with 14 experimental data set and analytical models of previousresearches. Comparisons were made using different error measures and it is found that the predictionaccuracy of the artificial network model is better than existing models.
Journal of Hydraulics
Iranian Hydraulic Association
2345-4237
3
v.
2
no.
2008
59
65
http://jhyd.iha.ir/article_85467_989045adcc01ed81d4c6a8e4aba6b98b.pdf
dx.doi.org/10.30482/jhyd.2008.85467
English Abstract
text
article
2008
per
Journal of Hydraulics
Iranian Hydraulic Association
2345-4237
3
v.
2
no.
2008
69
73
http://jhyd.iha.ir/article_85468_5b89dcd0200351dd00e49e04fcb279b3.pdf
dx.doi.org/10.30482/jhyd.2008.85468