فهرست مطالب

Journal of Water Sciences Research
Volume:2 Issue: 2, 2010

  • تاریخ انتشار: 1390/11/08
  • تعداد عناوین: 7
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  • Seyed Hossein Ghoreishi, Mohammad Reza Majdzadeh Tabatabai Page 1
    Sediment flushing of reservoirs is an operational technique, whereby previously accumulated sediments in the reservoirs are hydraulically removed by accelerated flow when the bottom desiltingoutlets of the dam are opened. In this research, the process of sediment flushing is simulated by a three dimensional numerical model in which sediment and flow interaction are reflected in the reservoirs. Reynolds Averaged Navier-Stokes (RANS) equations are solved numericallyby Finite Volume on a three dimensional grid and a standard k −e turbulence model is used.The resulting flow analysis is used as an input data for the sediment model. The convection diffusion equation for the sediment concentration is solved. The concentration equation derived by Van-Rijn is adopted as a boundary condition, resulting in a calculation of bed material load.The depth integrated mass balance equation is applied to find the bed changes. The results from the numerical model are compared favorably with the data from physical model studies available in the literature.
  • Hooman Hajikandi, Mohsen Hatami Page 9
    In this paper twelve different empirical resistance coefficients expressed in terms of Manning's roughness are used apiece in seventeen known compositing methods. The data obtained from ten different cross-sections of the Sefidrood River, Iran, are used for the evaluation of the empiricalformulas. The present case-study is selected from a reach with gravel bed topology. Then no remarkable bed form exists. Comparison of the calculated discharges and resistance coefficients with measurements shows that the Keulegan formula used simultaneously with the Brownlieformula in different compositing methods results in highly over estimated discharges, while the Meyer-Peter & Muller, Marion, Chien-Mai formulas in conjunction with the total force approach match best with the measurements. Also comparison of the calculated discharges from empirical formulas in individual sections reveals that Chien-Mai and Subramanya formulas have the least discrepancies from measurements.
  • Hamidreza Vosoughifar, Alireza Daneshkhah Page 21
    In this research, the numerical method of computational fluid dynamics and dimensionless parameter of Froude number have been applied to determine the flow regime over ogee spillways.Froude number is a dimensionless dynamic parameter calculated using the square root of the ratio of inertia force and gravitational force. Considering that the study of the regimes of flow over hydraulic structures especially spillways is of great importance, and as the most applied spillway is ogee one, therefore it is required to study such structures. To study the sensitivity of the dimensionless parameters of Froude number and velocity using in the proper calculation of the profile of the flow over ogee spillway the software of fluent computational fluid dynamics softwarehas been used. Based on Gauss–Seidel convergence condition applied for the convergence and control of equations, the step time of 0.01 second, quad pave meshing and RNG k– turbulence model have been used. The results of this research shows that the decrease of reference designhead by 10, 20, and 30 percent leads to the decrease of reference average Froude number and reference average velocity of the flow over ogee spillway by 7.646, 15.2 18.835, and 6.519, 12.787, and 26.113 percent respectively. Moreover, the increase of the average Froude number of flow by 6.519, 12.787, and 26.113 percent, and average reference velocity by 13.933, 4.211, and 1.839 causes the reference design head to increase by 10, 20, and 30 percent. Whereas p-value of the profile of the flow in SPSS software is around 0.006 and very lower than 5%, it can be claimed that the numeral study is of high precision. In conclusion, the results obtained from numerical simulation have been provided and compared with the existing numerical and laboratory studies. The accuracy of this research is describable.
  • Mohammad Ali Bayat, Hossein Babazadeh, Mohammad Manshouri Page 31
    Water use productivity is one of the most important factors in scientific agriculture. It is equal to 0. 7 kg of production per cubic meter of irrigation water (Kg/m3) in Iran which is very low in comparison with advanced countries (1 to 2 Kg/m3). Current research studies temporal and spatialchanges of water use productivity in Hamedan province in Iran using Geographic Information System (GIS), as to find evapotranspiration values for wheat and to transform it to raster level using Inverse Weight Distance Interpolation (IDW) in ArcGIS9.2 software. As location and time dimensions are studied simultaneously, combination of both leads to more effective analysis.Evapotranspiration is the denominator of water use productivity and the nominator is products’ performance which the values are obtained using statistics of Iran Agriculture Ministry and Hamedan province Agricultural Organization in particular and location extension map for wheatproductivity is obtained from overlay of 2 raster of evapotranspiration layer and the performance layer.
  • Neda Faghihi, Fereydoon Kave, Hossein Babazadeh Page 39
    Regarding to increased use of groundwater resources, it seems necessary to have more accurate knowledge of characteristics of aquifers in order to improved usage and accurate management of these resources. In this study, we simulated groundwater flow of Qazvin aquifer usingVisual MODFLOW model, collecting data and statistics, as well as using different studies. The simulation model has operated and it has calibrated through changing the input parameters in logical range and comparing the results to level of the groundwater in observation wells. calibratedmodel has been administered in one year and then it got to validate. We planned different scenarios which is possible to occur in future. Then we predicted the reaction of aquifer to these environmental stresses by implementing the model and they have considered by hydrographicframe of average groundwater level for each scenario separately and the results compared to each other. At end, the results of annual water table balance of aquifer are studied and explained.
  • Mojtaba Saneie, Faranak Omidi, Ramin Fazlola Page 47
    One of the important issues in hydraulic engineering is inspection of local scour depth around bridge pier. Using piles is one of the ways for confronting local scour and erosion. In this study, the experiments were conducted in an 8m long, 0.5m deep and 0.25m wide flume. And the effectof using piles and number of them observed on the amount of scour in three different Frude numbers. The shape of the pier was a rectangle cube with 5cm long and 2.5cm wide. The diameter of the piles was 6mm, and piles were non-submerged. The results of experiments indicatedthat the use of different number of piles in three different Frude number, (0.214, 0.237, 0.297), reduced volume and depth of scour highly. It is observed that 3 and 4 piles in each three Fr number, (0.214, 0.237, 0.297), had better results in comparing with 2 and 5 piles. And also the lowest amount of scour and the highest efficiency were related to Fr number of 0.214, so the maximum scour depth and volume were reduced by 76% and 92% respectively in comparison with the pierwithout sacrificial piles. While these amounts in the Fr number of 0.237 were 88% and 66% respectively and in the Fr number of 0.237 were 88% and 52% respectively.
  • Ali Khosronejad Page 57
    In the present paper, a 3D numerical model has been applied to predict the flow hydrodynamics around power intakes within the Dez dam reservoir. The Dez dam is a 203 m high, double arch concrete dam which is constructed by Italians in 1962. Since then, sedimentation in reservoirhas continued and since the dam does not have bottom outlet, the reservoir bed level is raising by a rate of about 2.5 meter per year. The power intake invert level is in 270 m asl and on the basis of 2007 hydrography results, the reservoir bed level has reached the level of 260 m asl that means the sediment level is just 10 meters below the power tunnel intakes. The applied three dimensional model is a finite volume model, which can model curvilinear and non-orthogonal domains and uses the fully 3D time averaged Navier Stocks equations. For incorporating the effects of turbulent flow in computations, an advanced turbulent model, named k −w model has been applied. The present model results for flow field around power intakes show that for the present conditions (sediment level of 260 m and intakes level of 270 m) some limited amount ofsediments is entering power tunnels and if no rehabilitation measures is considered, more sediment will enter the power tunnels in the coming years.