Anisotropy Feature Analysis of the Flow Field Around Straight and T Shaped Spur Dike
mojtaba
mehraein
هیات علمی دانشگاه خوارزمی
author
text
article
2016
per
In thispaper the anisotropy features of the flow field around straight and T shaped spur dike were analyzed experimentally. Two different experiments were conducted for flow field around T shaped and straight spur dike at Tarbiat Modares University. Results show that the anisotropy features of the straight and T shaped spur dikes are almost the same. In the upstream section of the flow the turbulence almost has 2-components and in the mean flow levels the flow turbulence is more 3-component form as compared to the near bed levels. Near the outer bank the most 3- component turbulence were observed. This may be due to the small secondary flow formation in this region. In the web section and near the spur dike nose the turbulence is near to 3-component feature as compared to the middle of flow depth. This is because of the horse shoe vortex formation that was formed due to the interaction of the approaching flow and the down flow in the upstream face of the spur dike web. In the downstream section and in the shear layer region the anisotropy feature predominate (1-component turbulence). In the recirculation zone the turbulence is closer to the 3-component features and this is more pronounced in the middle levels. Far away from the shear layer the turbulence of the flow is close to the 2-component turbulent features as compared to the recirculation region. For anisotropy analysis, AIM and BM approaches are almost the same but the anisotropy element shape more coincides with BM approach. However, more experiments are needed to confirm this argument.
Journal of Hydraulics
Iranian Hydraulic Association
2345-4237
11
v.
1
no.
2016
1
19
http://jhyd.iha.ir/article_41482_a0d40d65f37755b1dd0205d8b89ed965.pdf
dx.doi.org/10.30482/jhyd.2016.41482
An Optimal Design for Dimensions of Water Diversion System in Dams using and Analyzing Hydraulic Uncertainties and Hydrologic Risk
mohamad
karamouz
Professor, School of Civil Engineering, University of Tehran, Tehran, Iran
author
siyamak
doroudi
M.Sc, Engineering Department, Islamic Azad University Science & Research Branch , Tehran, Iran
author
ali
moridi
Assistant Professor, Technical and Engineering Campus of Shahid Beheshti University
author
text
article
2016
per
Designing water diversion system has been a challenge for dam designers due to its much work as well as heavy costs. The transit capacity of diversion systems and the method by which a dam should be designed would be studied by scholars. In this study, a model is introduced for optimizing the dam water diversion system through two approaches. The first approach is conducted by the same principles of consulting plan as well as the optimization methods for optimal diversion system. In the second approach, with an eye to the uncertainties of hydraulic parameters and hydrological risk analysis, a numerical model is presented based on the initial costs of the project, the failure costs and the general risk of the system. Next, in both approaches, employing an optimal genetic algorithm and a suitable cost function which includes the cost of building the diversion system, dam and the cost of system damage due to the flood, the most appropriate diameter, level, the cover material, the length of tunnels and the height of upstream cofferdam and the height of downstream cofferdam will be determined. It is also determined whether the upstream cofferdam should have overflow. In this study, the Karoun Dam 4 in southwest of Iran is selected as the case study. The characteristics of the consultant plan for the height of upstream cofferdam, height of downstream cofferdam, and the tunnel diameters are 40, 20, 9.5, and 9.5 meters respectively. The results indicated that height of upstream cofferdam, height of downstream cofferdam, the tunnel diameters are 38,16,9.5 and 9.5 meters respectively for the first approach. They are 33, 5, 9, and 9 meters for the second approach. Thereby, the second model has the lowest annual expected cost compared with that of the consultant plan.
Journal of Hydraulics
Iranian Hydraulic Association
2345-4237
11
v.
1
no.
2016
21
34
http://jhyd.iha.ir/article_41484_ee3bde03bec3f1bc1514ee1b36a26da1.pdf
dx.doi.org/10.30482/jhyd.2016.41484
Design of the River Stable (Regime) Flow Section by Imperialistic Competitive Algorithm
M.
Karimi
دانش آموخته کارشناسی ارشد، دانشکده مهندسی عمران، آب و محیط زیست، دانشگاه شهید بهشتی، تهران
author
M. R.
Majdzadeh
استادیار دانشکده مهندسی عمران، آب و محیط زیست، دانشگاه شهید بهشتی، تهران
author
Mojtaba
Shourian
استادیار دانشکده مهندسی عمران، آب و محیط زیست، دانشگاه شهید بهشتی، تهران
author
text
article
2016
per
One of the challenges in river engineering design, planning and training is prediction of stable hydraulic cross section in which the rate of erosion and sediment transport is in a regime state. The instability problems of rivers cannot be properly evaluated without knowledge of the stable state. In this study, a simulation-optimization model of hydraulic geometry (stable geometry) was developed to predict the response and stable geometry of sand bed rivers. The model consists of an analytical model which will be solved using the Imperialistic Competitive Algorithm (ICA). Analytical simulation model is using the governing equations which describe the movement of water and sediment through a channel, calculate the distribution of the boundary shear stresses, and assesses the bank stability considering the effect of the vegetation. Two hypotheses of maximum sediment transport capacity (MSTC) and minimum stream power (MSP) are used. Simulation-optimization model of hydraulic geometry is used to determine the response of the channel geometry to variation in the bankfull discharge, sediment load, and the properties of the bank sediment. The river channel responses predicted by the model are shown to be in agreement with qualitative observations and empirical regime equations. Using the imperialist competitive algorithm in prediction of hydraulic geometry reduces computational complexity and makes it possible to take into account all parameters with reasonably good results.
Journal of Hydraulics
Iranian Hydraulic Association
2345-4237
11
v.
1
no.
2016
35
52
http://jhyd.iha.ir/article_41486_0e6150dfc9448861f1b6400f975c6370.pdf
dx.doi.org/10.30482/jhyd.2016.41486
Numerical Modeling of Flow Field around the Shaft Spillways Using Piano-Key Inlet
s.
nasiri
دانشجوی کارشناسی ارشد، مهندسی آب، دانشکده مهندسی عمران، دانشگاه صنعتی اصفهان
author
A.
Kabiri-Samani
دانشیار دانشکده مهندسی عمران، دانشگاه صنعتی اصفهان
author
K.
Asghari
دانشیار دانشکده مهندسی عمران، دانشگاه صنعتی اصفهان
author
text
article
2016
per
A shaft spillway is a hydraulic structure consisting of an entrance control structure and a vertical or inclined conduit discharging flow into the downstream channel. Morning glory spillway is a special case of vertical-circular crested shaft spillways. The shape of the weir crest and the upper part of the shaft are designed to follow the trajectory of the lower flow nappe. Morning glory spillways are used where other types of spillways are useless. However, limited discharge coefficient of morning glory spillways, results in increasing the water head in the reservoir and subsequently increase the risks of operation. Consequent to the onset of submergence, the head-loss increases, swirling flow generates, vortices intensify and the performance of spillway on evacuating flow decreases. Intake vortices are the results of angular momentum conservation at the flow constriction, where angular velocity increases with a decrease in the cross sectional area. The strong vortices over the inlet of the shaft spillway reduce the flow discharge considerably. A common solution for avoiding air-entrainment and swirling flow is to provide sufficient submergence at the intake. If the required approach flow conditions cannot be met to avoid the swirl and air entrainment, other structural approaches are considered. Anti-vortex devices are used as means of reducing the strength of vortex flow. The most economic and common measure to reduce the air-entrainment and swirling flow strength, is optimized shape of inlet e.g. by installing a circular Piano-Key (PK) inlet over the shaft spillway.
In this study, the flow field around the shaft spillways using PK inlet was investigated based on numerical modeling. Due to its special configuration, a PK inlet reduces the swirling flow strength and has significant effects on increasing the discharge coefficient of shaft spillways. The flow field around the structure and inside the vertical shaft spillway was modeled using FLUENT 6.3.26 software. For this purpose, the governing differential equations of motion in a cylindrical coordinate system were solved using finite volume method (FVM). Air-water two phase flow was applied on free water surface and standard k-e turbulence model was used. The model consists of a cylindrical tank of 2 m in diameter and 1 m high. A vertical shaft of 0.126 m in diameter was installed at the center of the tank floor equipped with the PK inlet. Accordingly, the effects of the PK inlet geometries, including the inlet length, height and angle on hydraulics of flow through the shaft and the flow discharge coefficient were investigated. The flow characteristics such as variations of pressure and 3-D flow velocities were calculated. Results show that, PK inlets increase the flow discharge considerably compared to a simple shaft or even a morning-glory spillway. Finally, the best geometries of PK inlets were suggested to achieve the maximum efficiency of the vertical shaft spillways.
Journal of Hydraulics
Iranian Hydraulic Association
2345-4237
11
v.
1
no.
2016
53
66
http://jhyd.iha.ir/article_41487_05fc791dc58ed15e3faa0b650e9308a1.pdf
dx.doi.org/10.30482/jhyd.2016.41487
» Research Note «
Application of Data Mining Approaches for Estimation of Pile Group Scour
somayeh
soltani-gerdefaramarzi
هیات علمی دانشگاه اردکان
author
روح الله
تقی زاده مهرجردی
هیات علمی دانشگاه اردکان
author
text
article
2016
per
Pile groups are widely used as the foundation to support marine structures in coastal and ocean engineering. Clearly, scouring at the piles is of importance in connection with the stability of the structure leading ultimately to its failure. An accurate estimation of scour depth around a pile is very difficult due to the complex behavior of flow around a pile structure on an erodible bed. The main objective of this paper is to investigate the method and equations that are developed for wave scour depth estimation and assessing the accuracy of these methods in comparisons with real data. Developing an accurate methodology for scour depth determination using soft computing techniques such as, Regression, neural network, decision tree, genetic programming and Neuron-Fuzzy inference system were also of great interest in this study. The results show that the existing empirical formulae does not have the required efficiency for wave scour depth estimation. The best of such models have an R2 = 0.57, RMSE = 1.29 and EF= - 48.86 whereas the proposed ANFIS approach produced excellent results with R2 = 0.94, RMSE = 0.04, and EF=0.97 when compared to the existing predictors for wave scour depth. The proposed methodology is a new approach in estimating wave scour depth in streams and can be combined with mathematical models.
Journal of Hydraulics
Iranian Hydraulic Association
2345-4237
11
v.
1
no.
2016
67
75
http://jhyd.iha.ir/article_41488_c6f3d55f97634b1703ddaa9e155c0d0e.pdf
dx.doi.org/10.30482/jhyd.2016.41488
» Research Note «
Dimensionless Longitudinal Profile of Free Hydraulic Jump
Amir
Gord-Noshahri
PhD Candidate of hydraulic structures, Dept. of Irrigataion and Reclamation Engineering, , Faculty of Agriculture and Engineering Technology, University College of Agriculture and Natural Resources, University of Tehran, Karaj, Iran
author
Ebrahim
Amiri Tokaldany
Professor, Dept. of Irrigataion and Reclamation Engineering, Faculty of Agriculture and Engineering Technology, University College of Agriculture and Natural Resources, University of Tehran, Karaj, Iran
author
text
article
2016
per
The longitudinal profile of hydraulic jump is the main factor in the design of stilling basin side walls and its bottom thickness. Therefore, the study of jump profile is of great interest. Researchers have developed several methods for jump profile prediction, but in practice there are some parameters in these methods that make their measurement difficult. In this study, a new simple equation has been developed for prediction of hydraulic jump profile with the mean error of 5.08%. The length of hydraulic jump has been used as non-dimensionalization factor in this equation. The comparison of the new equation with the previous studies showed good agreement in a wide range of Froude numbers, from 2.0 to 11.3.
Journal of Hydraulics
Iranian Hydraulic Association
2345-4237
11
v.
1
no.
2016
77
85
http://jhyd.iha.ir/article_41503_1e19fa88e0e02117e6fedd02b567dad5.pdf
dx.doi.org/10.30482/jhyd.2016.41503