Editorial
Volume 17, Issue 67 , March 2017, Pages 1-4
Original Article
maryam omrani
Abstract
Proper operation of irrigation networks because of population growth and limited water resources is essential. The poor operational performance of irrigation systems is partly a result of improper distribution of water to the tertiary units and branches. Progress of computers and numerical methods caused ...
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Proper operation of irrigation networks because of population growth and limited water resources is essential. The poor operational performance of irrigation systems is partly a result of improper distribution of water to the tertiary units and branches. Progress of computers and numerical methods caused developing models for flow simulation and optimizing water distribution in irrigation networks. In this study, the genetic algorithm has used in order to determine the optimal schedule of water distribution in BLMC channel of Bilavar network, located in Kermanshah Province. The optimal schedule of water distribution was presented in form of single purpose, including minimizing the difference between the delivery and required amount of water for each farms. Initially, the genetic algorithm parameters and operators impact on the objective function were studied using sensitivity analysis. Suitable values for number of generations, population size, crossover and mutation probability for optimizing water distribution determined 250, 200, 90% and 1%, respectively. In case that water pump on and off occurs every 24 hours, differences between delivered and needed volume of water for all farms in Bilavar network, during second decade of April and early May, are 28910 and 14130 cubic meters, respectively.
Original Article
Ghorban Mahtabi; Yaser Mehri
Abstract
One of the main reasons of destructing the coastal slopes and riverbanks is failure of side slopes under the rising the water table or sliding the side slopes under the drawdown of channel water. In this research, effect of variations of water table and channel water level on the piping of coastal slopes ...
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One of the main reasons of destructing the coastal slopes and riverbanks is failure of side slopes under the rising the water table or sliding the side slopes under the drawdown of channel water. In this research, effect of variations of water table and channel water level on the piping of coastal slopes was studied and effect of cutoff wall on the phenomenon was investigated in the conditions. The experiments were conducted in a seepage tank with physical model of a trapezoidal section including 1.5 side slope and 0.58 mm mean diameter of the particles. Cutoff wall was fixed in the relative depths Z/d=0.5, 0.67, 0.83 and 1. Results of peak conditions of flood showed, in the control experiment, piping was observed in the all relative channel water level except the relative channel water level equal to y/d=0.7. In the experiment with cutoff wall Z/d=1 and without occurrence of piping, exit flow gradient was decreased approximately 41 present with respect to the control experiment. Results of drawdown conditions of flood showed, in the control experiment, piping was observed in the all channel water level. In the experiments with cutoff wall, in the cases with high water table, despite of existence of cutoff wall, increasing the exit flow gradient caused to piping in the all of the experiments because of increasing the hydraulic head. Other wise, in the experiment with the relative water table equal to h/d=0.933, piping was occurred in the all depths of cutoff.
Original Article
Abstract
Sharp crested weirs and sluice gates because of their ease making, water surface control potential and flow rate measuring have been broadly studied. Since the nature of flow on the weirs is highly complicated, mostly the driven equations are taken in account a series of simplifier hypothesis that are ...
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Sharp crested weirs and sluice gates because of their ease making, water surface control potential and flow rate measuring have been broadly studied. Since the nature of flow on the weirs is highly complicated, mostly the driven equations are taken in account a series of simplifier hypothesis that are on the base of empirical experiments. On the other hand most of the weirs cause a relatively calm zone of water on their upstream, which is a place of waste material and sediments to precipitate that is the disadvantage of the device. With gradual storage of sediments, the condition of flow changed and driven equations will lose their precision. In this case composition of weir and gate can be a useful solution for passage of floating materials over the weir and transmission of sediment materials from the lower part of the gate. In this study, hydraulic characteristics of the 18 combined model of trapezoidal weir-gate in the tree groups with three different opening gates at the end of an open channel with a circular cross section were studied. Using dimensional analysis, analytical solutions and statistical analysis, an equation for combined discharge by combined model of weir-gate was introduced and was evaluated by experimental data. The Results showed that the outcome discharge coefficient have a good agreement with experimental data.
Original Article
sina sadeghfam; Ali Rezazadeh Joudi
Abstract
The energy dissipation through hydraulic structure is an important issue in hydraulic engineering. The performance of hydraulic structure as a view of energy dissipation can provides the stabality of structure and river bed. In this study the experimental investigation of screen performance is evaluated ...
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The energy dissipation through hydraulic structure is an important issue in hydraulic engineering. The performance of hydraulic structure as a view of energy dissipation can provides the stabality of structure and river bed. In this study the experimental investigation of screen performance is evaluated as the energy dissipator of supercritical flow. The investigated parameters include: Froude number; screen porosity; location of screens. The Froude number of supercritical flow has been varied in the range of 2.5 to 8.5, and the screen porosities are 40 and 50%. Also the location of screens has been considered 62.5, 125 and 250 cm after supercritical flow generator gate. The results indicate that screen porosity, location of screens from supercritical flow generator gate and also Froude number of supercritical flow have a significant effect on screen performance. The energy dissipation of system through screens is more than free hydraulic jump in the entire evaluated cases. The results show that the Froude number increasing result in screen performance (relative energy dissipation) increasing, but screen efficiency (difference between the relative energy dissipation of system from free hydraulic jump) decreasing. Also the screen with 50 porosity which has been located at 125 cm from gate has the best performance.
Original Article
Abstract
Labyrinth weirs are often a favorable design option to regulate upstream water elevations and increase flow capacity; nevertheless, it can be difficult for engineer to optimal design due to the complexities of nappe behavior, many geometric design and hydraulic variables. A level of sedimentation in ...
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Labyrinth weirs are often a favorable design option to regulate upstream water elevations and increase flow capacity; nevertheless, it can be difficult for engineer to optimal design due to the complexities of nappe behavior, many geometric design and hydraulic variables. A level of sedimentation in upstream and submergence in downstream of the weirs are parameters, which affects on the performance of these structures. In this research the effect of different levels of tail water (one third and two third of weir height) and upstream sedimentation level (non-sedimentation and in sedimentation level of 90 percent of weir height) on the discharge coefficient of different geometers of trapezoidal labyrinth weirs for two conditions, that was investigated experimentally. The analysis of results indicated that increasing tail water depth to one third of weir height didn’t affect on the discharge coefficient of weirs. by increasing tail water depth to two third of weir height, air cavity volume under nappe decreased. Therefore, the flow pattern of the nappe changed from leaping to clinging condition and upstream head decreased. As a result, the labyrinth weirs discharge coefficient in non-sedimentation and sedimentation level of 90 percent of weir height increased about 3.3 to 12.2 and 2.1 to 9.2 in maximum discharge, respectively in comparison un-submergence tail water. The statistical equation for estimation of the discharge coefficient of trapezoidal labyrinth weirs for upstream sedimentation and submerged conditions was developed.
Original Article
Navid Khayat; Ahad Nazarpour
Abstract
Consolidation and stability of soil is influenced by the presence of minerals in the soil and it is especially related to its moisture and this is a prevalent difficulty in the construction of irrigation and drainage networks. In this research, the effect of natural gypsum on the properties of soil in ...
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Consolidation and stability of soil is influenced by the presence of minerals in the soil and it is especially related to its moisture and this is a prevalent difficulty in the construction of irrigation and drainage networks. In this research, the effect of natural gypsum on the properties of soil in the location of constructing network was studied. In order to achieve answers which comply with the conditions of operation, samples were prepared from the construction site, where they contain natural gypsum in soil. Samples were selected, based on a weighted combination of soil and natural gypsum, with percentages of 1%, 4%, 10% and 15% and by conducting standard chemical tests to determine the percentage of gypsum and some general properties of soil. In order to assess the rate of dissolution, consolidation test was also conducted and in this process EC was measured for a month in output water samples extracting from the process of replacing distilled water, in a one-day period and under the stresses of 1, 4 and 8 kg/cm^2 in the consolidation device. The results showed that by increasing the amount of gypsum, plasticity index and dry density of soil samples have decreased, but permeability and settlement rates have increased. Since in the calculation of settlement of gypsum-containing soils, in the addition to the percentage of gypsum, parameters such as volumetric compression ratio and stress are effective as well; so, these factors have been investigated in this research a formula has been suggested by considering these factors.
Original Article
Saeid Akbarifard
Abstract
Flood routing is one of the most complex problems that is investigated in open channel hydraulics and river engineering. Among the different flood routing methods, the Muskingum model, as the most common hydrologic method of flood routing, has been widely used with high accuracy in river flood studies. ...
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Flood routing is one of the most complex problems that is investigated in open channel hydraulics and river engineering. Among the different flood routing methods, the Muskingum model, as the most common hydrologic method of flood routing, has been widely used with high accuracy in river flood studies. The parameters estimation of the nonlinear Muskingum flood-routing model has been considered by different researchers and several methods have been utilized to this purpose. In this paper, the wolf search algorithm (WSA) was used to this end. To assess the optimum values of Muskingum parameters, the objective function was defined as the minimizing of the sum of square residuals between the observed and routed outflows. To investigate the desirability of research findings, the results of the WSA were compared with other heuristic algorithms including genetic algorithm (GA), particle swarm optimization (PSO), harmony search (HS), and imperialist competitive algorithm (ICA). Six benchmark functions with different dimensions were used to evaluate the capability of algorithms. The results showed that the WSA is capable to provide satisfactory estimates of nonlinear Muskingum parameters, so that, the values of R2 and RMSE were obtained 0.99261 and 2.419886 for Kardeh river and 0.778425 and 0.712358 for Wilson river, respectively.
Original Article
Fariborz Abbasi; Farahnaz Sohrab; Nader Abbasi
Abstract
Assessment of low irrigation efficiency in the country and providing appropriate solutions to improve irrigation efficiency and water productivity at the national level can be a great help for modifying irrigation efficiency. For this purpose, available data on irrigation efficiencies in different irrigation ...
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Assessment of low irrigation efficiency in the country and providing appropriate solutions to improve irrigation efficiency and water productivity at the national level can be a great help for modifying irrigation efficiency. For this purpose, available data on irrigation efficiencies in different irrigation systems and differnet irrigation networks (traditional and modern) were analyzed. Analysis was based on results obtained from about 200 field scale studies carried out in some provinces including 1900 measured irrigation events across Iran from 1991 to 2015. The finding showed that application irrigation efficiency (Ea) ranged between 22.5 and 85.5% and having meant of 56%. The averages of Ea in basin, border and furrow irrigation systems were 55.3, 52.9 and 52.5%, respectively. Eventhogh, Ea in sprinkler irrigation systems for example wheelmove and solid set systems were 66.9 and 52.1%, respectively. Average of Ea in pressurized and surface irrigation systems were 66.6 and 53.6%, respectively. As well as, Ea in sprinkler and drip irrigation systems were 62.1 and 71.1%, in order. Results also indicated that Ea over three decades (1992-2001, 2002-2011, and 2012-2015) were 52, 58.4, and 58.8%, respectively. However, network irrigation efficiency was 67, 68.5 and 74.2% in these 3 decades in order. As a result, total irrigation efficincey (Ep) was 29.7, 36 and 43.8% in these decaceds, respectively. This meant that, Ep had annully increased about 1% from 1996 to 2013.
Original Article
Peyman Varjavand; Mehdi Ghomeshi; Ali Hosseinzadeh Dalir; Davood Farsadizadeh
Abstract
Density currents are formed when gravity acts upon a density difference between two different fluids. These currents are the most important transport mechanisms and deposition of noncohesive sediments in narrow and deep reservoirs. In this research, 63 experiments were performed to investigate the effects ...
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Density currents are formed when gravity acts upon a density difference between two different fluids. These currents are the most important transport mechanisms and deposition of noncohesive sediments in narrow and deep reservoirs. In this research, 63 experiments were performed to investigate the effects of two shapes and three heights of artificial roughness on sediment-laden density currents. Velocity and concentration profiles were measured in the body of current. Results showed that presence of roughness causes 47% increasing in the density current body thickness, 29% decreasing in the maximum value of velocity and 163% increasing in the distance of peak value of velocity point from the bed in the normal velocity profile. Also for different roughness and with special hydraulic conditions, Lifting phenomenon has been observed, which is affected by densimetric Froude number, relative roughness and blockage factors. This phenomenon effects on the velocity and causes 5-25% increasing in the maximum value of velocityi the stream line of current. Sedimentation rate in the current over rough bed is approximately 223% more than smooth bed if lifting phenomenon has not be occurred.
Original Article
amir moradinejad; amirhamze haghiabi; mojtaba saneie; hojatola yonesi
Abstract
A major problem with which most of the lateral intakes are faced, is accumulation and sediments entering the intake entrance and diversion efficiency is reduced. Sediment control is one of the most important issues in river engineering. To reduce sediment entering the intake entrance can be From the ...
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A major problem with which most of the lateral intakes are faced, is accumulation and sediments entering the intake entrance and diversion efficiency is reduced. Sediment control is one of the most important issues in river engineering. To reduce sediment entering the intake entrance can be From the methods of controlling the Sediment entering to the intake entrance . In this study effect of the location, and angle of the spur dike and using skimming wall on the amount of delivered sediment into the lateral intake and intake ratio were testing. Effects of angle variations(30,45,60,90) of spur dike and spur dike location(b, 2b, 2.5b ,3b) on intake ratio and delivered sediment into the intake were investigated (b is the intake width ). Results show that discharge 60( lit/s), and spur dike with 60 degree angle and 2b distance from the center intake entrance in combination with the skimming wall compared to an angle of 30, 45 and 90 degrees, respectively, 27, 14 and 12 percent less sediment and 53, 45 and 16 percent superior discharge into the the intake diverts. Also by increasing the parameter the ratio of distance of spur dike, to the width of intake, Ratio of flow deviation to the intake for angle of 30°, 45°, 60° and 90°, and u ̅/u_c =1.05 for 5, 13, 2 and 23% Respectively, u ̅/u_c =1.08 for 2, 3, 3 and 2% Respectively , u ̅/u_c =1.11 for 17, 24, 2 and 10 percent Respectively increases.
