Journal of Irrigation Sciences and Engineering
Year:2018 | Volume:41 | Issue:2 |Papers Count:17

Simulation of lateral distributions of velocity and suspended sediment concentration in river bends is of great significance, and has many applications for river engineering projects. Due to secondary flow development, flow structure in river bends has 3-dimensional nature. As shown in Fig. 1, the secondary flow, coupled with the longitudinal primary movement, causes a helical flow that forms in the river bend (Perkins, 1970). In this case, 1-dimensional mathematical models (e. g. HEC-RAS, MIKE-11 and ISIS) are generally not satisfactory and 2 or 3-dimensional mathematical models should be used instead. However, the large amount of computational time needed to simulate flow field in rivers by 3D or 2D mathematical models, justifies the use of quasi 2D modes. Among the numerous quasi 2D models, the Shiono and Knight model has attracted great attention of river engineers. This mathematical model is based on the depth averaged integration of Navier-Stocks equations. Due to suitable form of in this study, at first with field measurement of lateral distributions of velocity and suspended sediment concentration in three bends located at the Karoun river (namely Maliheh, Jangieh and Khabineh), the Shiono and Knight quasi-two dimensional model (1991) has been calibrated. Using the lateral velocity profiles obtained by this mathematical model, sediment transport capacities were computed. The results showed that in all three river bends, among the empirical sediment equations selected for this study, the sediment transport equation of Yang has very well agreement with the measured lateral suspended sediment concentration, in comparison to the Ackers-White and Engelund-Hansen equations...

Hydraulic jumps are the most important type of rapidly variable flow that occur in from the supercritical state to the subcritical state with the sudden increase of the water free surface in a relatively short path, and usually has a high kinetic energy dissipation. The presence of a barrier against the flow will result in the separation of the inlet jet and more energy depletion resulting in increased shear stress and increased drag force. As a result, the jump length and conjugate depth decreases. These obstacles must be structurally sound because they are directly in front of the jet. If the flow rate exceeds 17m/s, it will cause a cavitation phenomenon (peterka, 1985). Another factor that can reduce the dimensions of a hydraulic jump is the roughness of the floor. Rajaratnam(1968) conducted the first systematic studies of jumping on a rough bed. The results of Rajaratnam were confirmed by Hager(1992), and, with their study of acoarsebed, Ead and Rajaratnam(2002) showed that the jump length on the rough bed is almost three times the conjugate depth (Lj/Y2=3). Shows that the rippling bed has halved the length of the jump to the length of the USBR-I pond. Studies on roughened bed reveal that the use of rough substrates requires more experiments to determine the proper shape of roughness. Hence, in this study, roughnesses in cubic, triangular and cubic and triangular combinations with zigzag arrangement have been investigated on the hydraulic jump specification in the rang of 5. 13 to 9. 75 froud numbers.

Iran is located in arid and semi-arid areas of the world and the major factor in this region is water shortage. The shortage of water in the country has limited food production and agriculture activities. More than 94 percent of the water resource of this country is used in agriculture sector, but the overall efficiency of irrigation in the country is between 33 and 37 percent. Therefore, despite the water crisis in the country and regarding the low turnover in irrigation, efficient use and management of water in agriculture sector is unavoidable. One program that has been implemented by Jihad of agriculture ministry in villages and cities to increase the efficiency of irrigation in agriculture sector is optimal water consumption plan In this plan, water demand for producing each yield unit is taught to beneficiaries to avoid excessive water in irrigation. This study aimed to suggest strategies for the development of this plan in the country. These strategies presented by SWOT method and prioritized by QSPM matrix. Nuga and Asimiea in 2015 used this technic to analyze agriculture sector in Niger. Based on results, the usage of international budget for developing of environmental educations in villages introduced as the most significant strategy, having the highest score...

'Transition' is a short hydraulic structure used to change the cross-sectional shape or flow shape. Transitions are commonly used both in the open-channels and natural waterways. The task of a transition is to connect a narrow channel at the upstream to a wider downstream channel or viceversa. This, creates a disturbance region of turbulent flow causing energy losses. In general, the structure of a transition prevents the formation of wave and other turbulencies. In this case, the energy loss, due to the change in the amount of the momentum, will be minimized...

A Stilling basin with divergent section has better performance and lower constructional costs than the classic basin. It can easily adapt itself to the upstream and downstream conditions in terms of depths and cross sections (Omid et al., 2007). Khalifa and McCorquodale (1979) studied radial hydraulic jumps in a gradually expanding channel of rectangular cross section and developed a theoretical equation assuming a second degree polynomial for the surface profile. Omid et al. (2007) studied the hydraulic jump formed in a gradually expanding stilling basin of trapezoidal cross section. They also investigated the hydraulic jumps for three different basin side slopes. Their experimental results indicated that the divergence of the basin for a given side slope causes reductions in the sequent depth and jump length, and an increase of the energy loss in jump relative to those observed in rectangular cross sections. Sahebi (2013) simulated a divergent hydraulic jump in rectangular basins using standard and RNG turbulence models. The outputs of the numerical model showed that the standard turbulence model evaluated the free surface of flow, jump length and maximum velocity in defined sections better than RNG turbulence model. In this study, for seven Froude numbers in the range of 3. 2-9. 1, three models of the divergent basins were numerically simulated at three dimensional conditions with various geometries of divergence angle and wall type. The k-ε RNG and RSM models were used for turbulence analysis and volume of fluid (VOF) model was used for simulating of free surface profile in the Fluent model. Also, vertical distributions of turbulence intensity, Reynolds stresses and turbulent kinetic energy were investigated using the RSM model in various sections of the hydraulic jumps...

Irrigated agriculture is the main user of the available water resources. About 70% of the total water withdrawals and 60-80% of total consumptive water use are consumed in irrigation (Sepaskhah and Ahmadi, 2010). Due to changes in climatic parameters and reduction of available water resources, The application of water saving strategies such as deficit irrigation with choosing suitable cultivation system compatible with ecological characteristics of the area such as intercropping, can reduced water use consumption. Many researchers have studied the effects of these methods on some components of yield and water use efficiency (Anderian, 2004; Caviglia et al, 2004; Filho, 2000; Tahir et al, 2003). In recent years, the concept of alternate partial root-zone drying irrigation has been raised and attracted considerable interest. Partial rootzone drying technique (PRD) is a modified form of deficit irrigation which involves irrigation only one part of the root zone in each irrigation event, leaving another part to dry to certain soil water content before rewetting by shifting irrigation to the dry side (Sepaskhah and Ahmadi, 2010) that this technique has been less investigated in intercropping system. The objective of this study was to investigate the effects of regulated deficit irrigation (DI) and partial root-zone drying (PRD) on yield and some components of intercropping Sorghum-Red bean...

In the present research, the flow on a free dam is modeled in 3D environment of Flow-3D software, then the software results were validated in comparison with results obtained from the physical model. Finally, the effect of various types of ramps on effective factors of vacuum creation was scrutinized. The results for vacuum creation index and air concentration existing within the flow revealed that a spillwaywith ramp at the bed and a wall equipped with duct, and a spillway with ramp at bed and wall, leads to %22, %22 and %19 increase in vacuum creation index, respectively...

Water intake from the river is done using several methods. Each method has its own features and limitations. In steep mountain rivers with irregular bed, high values of sediment transport and flash floods may prevent the application of gated dams; therefore, the bottom intakes are often used. In this method, in some part of the river width and length, a trench is created with a proper cross section and water is flowed through this trench into the diversion channel. In order to prevent the coarse particles to enter, top of the trench is covered with bottom rack bars. Corrosion of the bars, clogging, and maintenance are the common problems of bottom racks, which make them unusable in long term. To solve these problems, a new system of bottom intake with porous media is introduced. In this method, after trenching in the river bed, materials with appropriate aggregation are dumped in the trench and water intakes from the river through a diversion channel. This means that a portion of flow into the porous media; then move to the diversion channel. Another portion of the water passes over the bottom intake and finally drive to the river. Usage of the porous media has, however, many limitations; but it has some advantages, such as, no suspended solids in the water, respect for the environmental problems, no change in natural morphology of the river, withstanding in different weather conditions, and dealing with the problem of freezing, and corrosion, easy to construct and applicability, affordability and availability of materials...

The study area (Lavar plain) is part of the Kol River catchment and is located about 60km in North of Bandar-Abbas, in Hormozgan province, south of Iran. The study area lies between longitude of 56º 51´ 6´ ´ – 56º 1´ and Latitude of 27º 32´ 22´ ´-27º 36´ . The area’ s elevation ranges from 240 m to 2900 m from sea level (Fig. 1). The climatic condition of this study area is influenced by medium elevation (240 m) above the sea level. As it is normally hot, temperatures are not below zero. Additionally, the study area is affected by the air mass systems mentioned above, whereas the first and third portions are more influential on precipitation. The main rainfall is related to cyclones that pass from western to eastern direction. The majority of cyclonic activity originates from the Persian Gulf, normally from January to March. Laver Dam is located in the eastern part of the plain. The dam is constructed on the river that is collecting runoff from the two sub-basins of the Sarzeh-Rezvan and Gnou in the reservoir of the dam. The groundwater aquifer is an unconfined aquifer with an area of 23. 5 square kilometers and surrounded by sandstone formations and conglomerate. The study area is located in the Zagroos folded zone. In the study area, the oldest formations are of Paleozoic age. Another characteristic of the Zagroos zone are diapers. Diapers rise up from the deepest part of sedimentary rocks, and after cutting through the upper layers, they may appear at the surface, which seriously affect groundwater quality and land use...

Limited water and soil resources and growing population have led countries around the world towards raising agricultural production per unit area and optimal utilization of these resources. Due to the population growth and rising living standards, the demand for food has increased. In this regard, identification and knowledge of the parameters that somehow affect food production is essential. Using new techniques for selecting appropriate land irrigation methods can enhance water use efficiency in farm lands. Selecting a proper irrigation method in irrigated agriculture in order to achieve a high efficiency and maximum water use. Nowadays Fuzzy systems are one of the most efficient methods in the field of forecasting and modeling (Akbarzadeh et al, 2009). Fuzzy system is able to use human language and human experiences and experts and connoisseurs (Karatalopoulos, 2000). Sys, Vanranst and Debaveye (1991) proposed parametric evaluation system to select irrigation methods based on physical and chemical properties of soil. Using fuzzy logic capabilities which stem from the ability of continuous membership function of input variables and by combination of parameters affecting irrigation methods evaluation in parametric system with fuzzy logic membership functions, it is possible to assess farm lands for choosing the right irrigation method more accurately. Therefore, this study aims to utilize the functionalities of fuzzy logic method to evaluate land suitability of the area studied based on parametric system for two drip and sprinkler irrigation methods...

Derived Information from the predicted waves will be the basis for engineering design and plays an important role in the construction, maintenance and management of coastal and offshore construction projects. The wind-induced-waves due to having high energy and frequency are of great importance in the sea. In this research, the adaptive network based fuzzy inference system was selected to predict the waves’ characteristics. . Study About prediction of wave Characteristics is carried out by several researchers. Zarghani et al (2006) studied the characteristics of wind-induced waves at the coast of Khark island They used the SPM model to conduct the survey. The results obtained from the model showed that the highest wave was 3. 7 m with rotation period of 6. 8 seconds. Taleghani and Amirteimori (2008) used the field data of the Caspian Sea waves measured by a waveguide buoy in an artificial neural network. Finally, the comparison of real data measured by the measurement systems with the results of the neural network is a good match that indicates the accuracy and speed of the method used in the short term. Kamranzad and Etemad Shahidi (2011) studied the prediction of wind-induced waves in Assaluyeh using the SWAN numerical model. The validation results of the model showed that the results of calibration model have a good accuracy...

Drought prediction in water resources systems plays an important role in reducing drought damage. In recent decades, Traditional methods including: fitting and mathematical models have been widely used to predict droughts. The combination of wavelet theory and neural networks has led to the expansion of the wavelet-neural networks. The application of the wavelet as training function in the neural network has recently been identified as a substitute method in neural networks. In these models, the position and scale coefficients of the wavelets are optimized in addition to the weights (Thuillard, 2000). Considering the importance of short-term drought prediction in water resources engineering and the nonlinear characteristics of the SPI series of three months, the purpose of this study is to present an Artificial Wavelet Neural Networks integrated model for predicting short-term drought at Bidestan station in Qazvin plain. In this research, Multi-Layer Perceptron (MLP), Radial Base Function (RBF), ARIMA time series, as well as Artificial Wavelet Neural Networks integrated model and Multi-layer Perceptron (WA-MLP) and Radial Bonding Function (WA-RBF) were used, which is done by analyzing the time series investigated by the wavelet transformation and the entry of these subseries into an artificial neural network. According to previous researches on drought prediction, short-term drought prediction (with the definition of a three-month standard rainfall index) using the combined model of Wavelet-Neural Network and comparing its results with artificial neural network and ARIMA time series models has not been compared. In this paper, five short-term drought prediction models have been compared and a better performance model has been introduced...

Accurate prediction of the river flow is an important element in the management of surface water resources, dam reservoir operation, flood control and drought. Selecting appropriate inputs for intelligent models is vital to increase the accuracy and efficiency of the models. Since river flow prediction is of great importance in water resources, researchers have been exploring different approaches over the past several decades. Various methods have been devised to predict the flow of the river over the past years. In general, we can classify conceptual models and data-driven methods. Over the past four decades, time series models have been widely used in river flow prediction (Dawson et al., 2008). Intelligent systems are used to predict nonlinear phenomena. The Bayesian Network and the Artificial Neural Network are among these methods. Ahmadi et al. (2014) studied the comparison of performance of support vector machine and network methods in forecasting daily flow of the Barandozachay River. The results showed that, both methods are close to each other and are suitable for river flow simulation. But in midrange forecasting and the minimum backup car model, it's much better than the business network model. Shannon entropy theory was first developed by Shannon and then widely used in various scientific issues. The purpose of this study is to use the Shannon Entropy Theory to find the best combination of input variables for artificial neural network and Bayesian network models to predict the flow. Therefore, for this purpose, the Sufi River of the studied area was selected.

A hydraulic jump is a sudden transition from a supercritical to subcritical flow with a broad range of turbulence Scales. The fluctuating nature of the flow such as oscillations of jump toe position and production of large eddies are visible in pseudo-periodic manners. Energy dissipation of hydraulic jump occurs with Low-frequency large scale pressure fluctuations which can cause damage and erosion and endanger the security of the structures. In the present study, the effects of discontinuous roughness elements of lozenge shape on the fluctuations of pressure in hydraulic jump have been investigated...

In reservoir of dams, especially near the dam body, the cohesive fine sediments are deposited mainly. The mechanical behavior of these sediments is largely controlled by the interparticle attraction caused by electrostatic and physiochemical forces. these properties cause the stickiness and accumulation of clay particles and formation of dense masses called flocs, which is sometimes referred to as flocculation. flocculation is influenced by several factors including salinity, flow regime, sediment concentration and organic matter. Flocculation is the most important factor that makes the settling, fall velocity and transfer of cohesive sediment considerably more complex and dynamic than non-cohesive sediments. In order to determine the relations governing cohesive sediments, the physical characteristics and behavior of these sediments should be identified. The terminal settling velocity of sedimentary particles in liquids, called particle fall velocity, is one of the most important properties in determining the physical properties of sediments caused transfer, deposition and consolidation. The fall velocity of cohesive sediments is influenced by many factors, including salinity, initial particle size, turbulence, temperature of water, and suspended sediment concentration...