مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resources
مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resources
مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resources
مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resources
مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resources
مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resources
مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resources
مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resources
Issue Info: 
  • Year: 

    2017
  • Volume: 

    9
  • Issue: 

    31
  • Pages: 

    1-10
Measures: 
  • Citations: 

    0
  • Views: 

    1539
  • Downloads: 

    0
Abstract: 

Bridges are one of the most important river structures. One of the main causes of bridge failure is local scour at bridge piers. Yearly, Many bridges failed around the world because of disregarding hydraulic factors. Hence, an accurate prediction of scour depth at piers is essential for the safe design of the bridge foundation. In this study, local scour at Aala Bridge (Ramhormoz) is investigated. The Aala Bridge crosses the Aala River near the city of Ramhormoz, Khuzestan province. We use one dimensional Saint-Venant Equation for simulation at river dynamic in FASTER model. For evaluation of scour depth, 14 scour equations in subroutines were added to FASTER model. Comparison between computed scour depth showed that equation of Froehlich (1996) appear to give a reasonable estimate of the local scour depth. Jain and Fisher equation (1979), Melville equation (1997) and Melville and Sutherland equation (1988) overestimate scour depth, and the other experimental equations are not suitable for this condition.

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Issue Info: 
  • Year: 

    2017
  • Volume: 

    9
  • Issue: 

    31
  • Pages: 

    11-20
Measures: 
  • Citations: 

    0
  • Views: 

    1252
  • Downloads: 

    0
Abstract: 

Evapotranspiration has a main role in water budget assessment and management. In plant water requirements and evapotranspiration volume calculation, firstly reference evapotranspiration (ET0) have to be computed and then plant water requirements can be estimated using different methods. In this research, firstly the reference evapotranspiration factor was calculated by standard FAO-Penman-Monteith formula via climatic data of Tabriz station, East Azerbaijan province. Climatic parameters include mean, minimum and maximum of air temperature also mean, minimum and maximum of relative humidity, rainfall, wind speed and sunshine hours were considered as an input of genetic programming and M5 tree models to estimation of monthly reference evapotranspiration as an output. Results showed that both of two approaches present exact results (determination coefficient for M5 tree model equal to 0.99 and for GP equal to 0.96) in estimating monthly reference evapotranspiration in Tabriz region, but M5 model tree, provides understandable, applicable and simple linear relations to estimate reference evapotranspiration.

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Author(s): 

AZIMI HAMED | SHABANLOU SAEID

Issue Info: 
  • Year: 

    2017
  • Volume: 

    9
  • Issue: 

    31
  • Pages: 

    21-33
Measures: 
  • Citations: 

    0
  • Views: 

    647
  • Downloads: 

    0
Abstract: 

Side weir is used as a slot in the side of main channel to direct excess flows that are above the weir crest. Such structures are used in control of flow level in irrigation, drainage networks and urban sewage disposal systems. Among these structures, circular channels are extremely important. Considerable length of sewage disposal and transmission pipeline system is made of circular channels. In this study, changes of water surface level, turbulence and flow field passing through a circular channel with side weir is simulated using commercial software. In this numerical simulation for modeling changes of flow free surface, VOF model and for simulating of the flow field turbulence, RNG k-ε turbulence model are used.  In this study in order to validate the accuracy of the numerical model, the flow depth changes along the side weir, the discharge coefficient of the side weir, the passing flow over the weir, the Froude number at the upstream of the weir and the specific energy at the beginning of the weir are compared with the laboratory results. Comparison of all mentioned parameters with the experimental results show high accuracy of CFD model in predicting turbulence and flow field of passing through a circular channel with side weir. The main purpose of this simulation is gaining an understanding of behavior of passing flow through circular channels with side weir in order to use in design problems of this type of hydraulic structures.

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Author(s): 

SOLGI EISA | MORADPOUR HABIB

Issue Info: 
  • Year: 

    2017
  • Volume: 

    9
  • Issue: 

    31
  • Pages: 

    35-44
Measures: 
  • Citations: 

    0
  • Views: 

    1087
  • Downloads: 

    0
Abstract: 

Groundwater contamination with nitrate is a pervasive problem in Iran and all over the world. Groundwater nitrate pollution associated with agricultural activity is an important environmental problem in the management of this natural resource, so that this is one of the most common groundwater contaminants. Determining the concentration and its spatial variation can be useful in exploitation and management of water resources. In this research, a total number of 50 wells were selected for sampling purposes and nitrate concentrations were analyzed in the laboratory according to standard method. Measured nitrate levels were compared to World Health Organization (WHO). Although, slightly increasing or decreasing changes in nitrate concentrations were observed in some wells, however the concentrations were below the standard of WHO (50 mg/L). It seems that nitrate concentrations in plain are affected by nonpoint sources (nitrogen fertilizers) and point sources (wastewater) that will undoubtedly be most important source of nitrate pollution in the future. Spatial patterns of nitrate showed that the highest concentrations of nitrate were found in north-eastern and south-eastern. Also, no statistically significant correlations were observed between nitrate concentration and well depth.

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Issue Info: 
  • Year: 

    2017
  • Volume: 

    9
  • Issue: 

    31
  • Pages: 

    45-60
Measures: 
  • Citations: 

    0
  • Views: 

    1731
  • Downloads: 

    0
Abstract: 

Groundwater resources are one of the most valuable natural resources. Therefore, in the recent years, the groundwater modeling is a powerful tool in management procedures, optimization and predicting of groundwater resources in future. The purpose of this study is the modeling of Toyserkan aquifer with MODFLOW that is a code in PMWIN software which is considered to be very efficient in groundwater modeling. The simulation was attempted for an annual period of 12 monthly stress periods (September, 2008 to August, 2009). This model was calibrated for first 10 months in simulation period and then was verified with observed data for next two months. Calibration results in steady and transient states indicate that, horizontal hydraulic conductivity and storage coefficient increases from north east to the south west in the Toyserkan plain. After verification to postulate the confidence from model’s ability for predicting the aquifer’s future conditions, two scenarios with 10 years length were defined. The first scenario is based on the current withdrawal trend and in the second scenario, irrigation efficiency which is increased up to 20 percent and therefore decreases in withdrawals was considered. A trend of decline in the groundwater levels in most of observation wells and increase in two observation wells, numbers 3 and 6 were observed.

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Issue Info: 
  • Year: 

    2017
  • Volume: 

    9
  • Issue: 

    31
  • Pages: 

    61-72
Measures: 
  • Citations: 

    0
  • Views: 

    770
  • Downloads: 

    0
Abstract: 

 The element-free Galerkin method (EFG) and the natural element method (NEM) are two well know methods in the computational mechanics and meshless methods. In this paper, a computational scheme using a variable domain and a fixed domain is presented based on coupling of EFG and NEM for analysis of two dimensional spillway flow under radial gate for the computation of the free surface profile and the flow rate of a 2D gravity fluid f low through a conduit and under a radial gate. The coupling between EFG and NE is achieved by using the natural element shape functions as the weight functions for the element free Galerkin method. In this method, contrary to EFG method, the imposition of the essential boundary conditions is straight forward and shape functions fulfill the Kronecker delta property. In this study, the fluid is assumed to be inviscid and incompressible. The validity of the proposed method is verified by comparing the results from EFG-NE simulation results with those obtained from finite element simulation and experimental results. It is concluded that the results obtained by EFG-NE method is in good agreement with those from FEM and experimental results. Therefore, the coupled EFG-NE method is capable to handle spillway flow simulation.

Yearly Impact: مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resources

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Author(s): 

NAZARIPOUR HAMID

Issue Info: 
  • Year: 

    2017
  • Volume: 

    9
  • Issue: 

    31
  • Pages: 

    73-90
Measures: 
  • Citations: 

    0
  • Views: 

    936
  • Downloads: 

    0
Abstract: 

Hydrological drought is defined as a significant decrease in the availability of water in all its forms appearing in the land phase of the hydrological cycle. These forms are reflected in various hydrological variables such as stream flow (including snowmelt and spring flow), lake and reservoir level, and groundwater level. A variety of indices and methods for characterizing hydrological drought have been devised. In this study, an index called Streamflow Drought Index (SDI) have been used for characterizing the severity of hydrological droughts. Investigation of the forecasting possibility of hydrological droughts has been carried out by two approaches. First, when the appropriate historical data are available, Markov chain method have been used. The main output of the methodology is the matrix of state transition frequency for a selected pair of reference periods under the hypothesis of a Markov chain for the underlying state process. In other words, the output is a single value of drought state while the probabilities of remaining in the same state or passing to other states in the next reference period are withdrawn from tables which have been obtained off-line. Since, in general, streamflow data are difficult to obtain in real-time, the possibility of using a meteorological drought index was investigated. More specifically, a linear function of SPI was found to predict SDI to an accuracy level which is sufficient for characterizing drought severity. This involves prior calibration of a simple regression equation with modified SPI as the explanatory variable and SDI as the explained variable. The methodology is validated using reliable data from the Nesa and Fashkoh rivers basin in the southwestern margin of Kavir-e Lut (Iran). The results indicate that calibration of rainfall and streamflow relations provides a good opportunity to forecasting of hydrological droughts states in the lack of river flow data. A key consideration is that in this basin, a high degree of successful prediction is observed for the wet period of October to March. In addition, due to lack of storage snow in this basin, which can compensate the deficit rainfall in dry period, drought states predicting for other periods is also possible by using Markov chain methodology.

Yearly Impact: مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resources

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Author(s): 

ZAKERI NIRI MAHMOUD

Issue Info: 
  • Year: 

    2017
  • Volume: 

    9
  • Issue: 

    31
  • Pages: 

    91-102
Measures: 
  • Citations: 

    0
  • Views: 

    996
  • Downloads: 

    0
Abstract: 

Rainfall data play an important role in hydrological sciences. Lack of sufficient or qualified data usually leads to unreliable and inadequate results. In such cases, synthetic time series, e.g., generated rainfall time series, are of great importance for performing the watershed management activities. In most previous studies, statistical methods such as those of Markov chain and ARIMA methods have been applied for the rainfall generation at a single site. As the rainfall spatial pattern has a significant effect on the flow hydrograph characteristics, multisite rainfall generation plays its vital role in hydrology. In the present research, the Spatio-temporal Neyman-Scott rectangular pulses (STNSRP) method was applied and fitted to 50-year daily data taken from 20 Rain gauges in the Walnut Gulch watershed, USA. Rain gauges were divided into real rain gauges (14) and virtual rain gauges (6), and the performance of STNSRP model was assessed. Different statistics such as mean, variance and probability of dry days were calculated and compared with both the generated and the observed rainfall time series.  The IDW method was used to produce rainfall maps using the generated rainfall values at real and virtual rain gauges. Results revealed that the STNSRP model has the ability to match the observed statistics adequately. Also, the rainfall map generated using the virtual rain gauges has less error as compared with the map generated from the rainfall values only at the real rain gauges.

Yearly Impact: مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resources

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