Original Article
Hydraulic
Kimia Akhavan; Manouchehr Heidarpour
Abstract
Extended Abstract
Introduction
Hydraulic jump is a type of rapidly varied flow in which the flow transitions from supercritical to subcritical. Incorporating rough beds at the channel bottom leads to the maximization of energy dissipation, resulting in a significant reduction in conjugate depth ...
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Extended Abstract
Introduction
Hydraulic jump is a type of rapidly varied flow in which the flow transitions from supercritical to subcritical. Incorporating rough beds at the channel bottom leads to the maximization of energy dissipation, resulting in a significant reduction in conjugate depth and roller length. These results have important implications for the cost-effective design of stilling basins, which commonly encounter hydraulic jumps.one feature that has attracted the attention of researchers studying jumps on rough beds is the velocity profile of the jump on rough beds. In this research, the effect of the arrangement of submerged vanes on the velocity profiles of the hydraulic jump in a stilling basin was measured for Froude numbers ranging from 4.8 to 9.14.
Methodology
Experiments were conducted in the hydraulic laboratory in a rectangular channel with physical dimensions of length 8 m, width 0.4 m, and height 0.6 m. Submerged vanes were used as roughness elements on the bed of the laboratory channel. These vanes are made of Teflon, and the geometry of a submerged vane, including its width (w), thickness (t), angle of attack (θ), and vane length (L), is one of the parameters affecting the characteristics of the hydraulic jump. For measuring the flow velocity, an instrument called a Pitot tube was used. In the present study, for 12 experimental models, velocity was measured at five cross-sections along the width, and at three points across the width in each cross-section. Measurements were taken at five points along the depth, with equal spacing ratios from the channel bed to the free water surface, and the readings were averaged across three different widths.
Results and Discussion
In general, the maximum velocity value decreases with distance from the beginning of the jump and occurs at a lower depth from the water surface. The bed with submerged vanes causes a reduction in the flow velocity magnitude, and its maximum value occurs at higher points compared to the classical jump. The significance of the non-dimensionalized velocity graphs lies in comparing the growth of the boundary layer across the cross-sections. The average value of δ/b is 0.62 and 0.72, and for 50 < x/D₁, the ratio δ/b lies above the average line. Due to the low effect of turbulence and secondary currents caused by the presence of submerged vanes, the boundary layer thickness is greater in regions of calm flow ( areas with lower velocity). At values less than 50, the ratio δ/b decreases compared to the average line. The results showed that the value of the non-dimensional boundary layer thickness parameter, δ/b, was 0.72, which was highest in the parallel arrangement of submerged vanes at an attack angle of 75° compared to angles of 45° and 90°. Meanwhile, this value was obtained in the butterfly arrangement with an attack angle of 45° and increased from 0.56 to 0.01 compared to what other researchers have obtained.
Conclusions
Therefore, the best characteristic for the non-dimensional boundary layer thickness parameter, δ/b, on artificial roughness was achieved with the butterfly arrangement and a 45° attack angle of the submerged vanes, which proved to be an influential factor. In contemporary hydraulic jump research, the use of advanced techniques, such as machine learning tools and numerical simulations using Computational Fluid Dynamics (CFD), is increasing. Simulating hydraulic jumps with CFD is a complex task and requires careful attention to turbulence modeling, grid accuracy, boundary conditions, and various other factors. It is essential to employ advanced techniques for comprehensive three-dimensional (3D) velocity and bed shear stress measurements. Conducting turbulence analysis will contribute to a more refined understanding of the underlying flow dynamics. Furthermore, the challenge of hydraulic jump stability on adverse slopes persists. Introducing roughness elements and sills can enhance hydraulic jump stability on adverse slopes. Investigating the potential effects of scale in such conditions is necessary.
Original Article
Pressurized Irrigation Systems
Samad Hosseinzadeh Ajirlou; Bijan Nazari; fariborz abbasi; Afshin Khorsand
Abstract
Extend AbstractIntouductionWater scarcity is one of the biggest challenges facing the agricultural sector in many parts of Iran, especially in arid and semi-arid regions. Increasing agricultural water productivity is not only a solution, but also an absolute necessity. Although solutions such as increasing ...
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Extend AbstractIntouductionWater scarcity is one of the biggest challenges facing the agricultural sector in many parts of Iran, especially in arid and semi-arid regions. Increasing agricultural water productivity is not only a solution, but also an absolute necessity. Although solutions such as increasing the area under cultivation and increasing yield per unit area, optimizing agricultural inputs, controlling population and optimizing consumption, and increasing imports have been proposed to address the challenge of food security, each of these cases has its own implementation limits (Nouri et al., 2023; Garofalo et al., 2025). Crop models are considered a valuable tool for the integrated simulation of processes affecting crop growth and for the evaluation of crop management options (Mabhaudhi et al., 2014; Wallach et al., 2019). Crop models that can accurately estimate various parameters of crop growth, soil water dynamics, crop water use and expected yield under different irrigation levels can also be a fundamental aid for the successful implementation of irrigation management practises with limited and full irrigation (Sandhu & Irmak, 2019). Therefore, the aim of this study was to calibrate and then evaluate the AquaCrop model to simulate the yield and water productivity of forage maize under furrow and tape irrigation in the arid and semi-arid regions of Iran (Alborz province). In addition, the ability of the model to simulate the yield potential of forage maize under agricultural management in the study fields was evaluated.MethodologyThe data required for this study was collected in 2016 on farms in the province of Alborz. The farms were visited in coordination with the management of the Agricultural Jihad and were examined and selected taking into account the parameters required for the study. Three farms were selected in the city of Karaj, one in the Seifabad district, one in the city of Hashtgerd and one in the village of Haji Abad. The farm in Karaj was divided into three different sections due to its larger area, different cultivation dates and different irrigation schedules. Since understanding the current situation is one of the most fundamental planning steps for evaluating and providing solutions to improve any system, this study was conducted in the form of field experiments and field farms with the aim of investigating and estimating the current status of irrigation water productivity under farmers' management, and the potential for growing forage maize in Alborz province. Water resources, the cultivated area, total irrigated land area, soil texture, soil salinity, and irrigation water salinity in each farm were investigated and measured. Additionally, some farm characteristics such as area, precise GPS location, irrigation method, irrigation water source, timing of water withdrawal and variations in withdrawal flow rate throughout the year, network type, and operator characteristics were recorded using compiled information recording forms. Results and discussionThe results for the average yield of fresh forage corn were 49.12 tons per hectare using furrow irrigation method and 60 tons per hectare using tape irrigation method. In furrow irrigation, the highest fresh crop yield was obtained at Karaj farm (2) with 60 tons per hectare and an irrigation water productivity of 6.61 kg/m³. The lowest yield was recorded at Karaj farm (3) with 35 tons per hectare, while the lowest irrigation water productivity was at Karaj farm (1) with 4.24 kg m-³. The highest irrigation water productivity, 13.4 kg m-³, was observed at Hajiabad farm using tape irrigation. Therefore, tape irrigation is recommended for optimal water resource utilization. The study also showed that the RMSE index was 2.44 tons per hectare, and the d-agreement index was 0.947, indicating the AquaCrop model's ability to simulate corn fresh weight accurately in the study area. There was a strong correlation between simulated and measured crop yield values, with a coefficient of determination of approximately 0.95. The relative error (RE) was 3.7%, which is considered acceptable.ConclusionThe results demonstrated that the AquaCrop model has a strong capability to analyze various management scenarios, predict performance under water-limited conditions, and optimize irrigation patterns. From a management perspective, the findings suggest that agricultural policies should shift focus from the "land productivity" index to the "water productivity" index. Additionally, providing practical training for farmers, promoting modern irrigation technologies, and utilizing simulation models like AquaCrop can play a crucial role in reducing water waste, enhancing crop yield, and ensuring sustainable production. Ultimately, implementing these strategies will not only improve water productivity but also serve as an effective step toward protecting water and soil resources and ensuring long-term food security.
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