Original Article
Abstract
Sewage discharged into an ambient water system such as a river or sea is a serious problem in irrigation and drainage networks. Concerns about pollution require decreasing the initial dilution for disposal of brine wastewater into ambient environments. A quick and effective way to dilute dense waste ...
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Sewage discharged into an ambient water system such as a river or sea is a serious problem in irrigation and drainage networks. Concerns about pollution require decreasing the initial dilution for disposal of brine wastewater into ambient environments. A quick and effective way to dilute dense waste flow is turbulence from a submerged jet. The present research investigated use of a buoyant jet at different vertical angles and fluid injection rates on dilution. Flow-3D was used for modeling. Angles of 30°, 37.5°, 45°, 52.5° and 60° were considered at concentrations of 10, 20, 30 and 40 g/l and different jet injection discharges. The experimental data was then used for verification and validation. The results showed that the RNG k-e turbulence model with an error of about 9.5% had acceptable accuracy in the prediction of jet trajectory properties of injection flow. These results also showed that increasing the length (LM) decreased the peak height of the trajectory curve. The quantitative findings showed that the difference between the distance ratio of the peak trajectory at a 45° angle was twice that of the 30° and 60° angles at the different densimetric Froude numbers. The maximum and minimum dilution values at the peak trajectory were 0.68 and 0.48, respectively. At the peak for the return point, the maximum and minimum values were 0.42 and 0.03, respectively.
Original Article
ali rezazadeh joudi; mohamadtaghi sattari
Abstract
The stability of bridge piers on rivers or in wide and deep irrigation channels is a major concern for hydraulic structural engineers. Despite development of several empirical equations for determining local scour depth at bridge abutments in hydraulic laboratories, for field data, which is affected ...
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The stability of bridge piers on rivers or in wide and deep irrigation channels is a major concern for hydraulic structural engineers. Despite development of several empirical equations for determining local scour depth at bridge abutments in hydraulic laboratories, for field data, which is affected by uncontrollable environmental circumstances, no comprehensive relationship has been reported. Gaussian process regression (GPR) is a data mining method consisting of a set of random variables that, according to normal characteristics using kernel functions, have a high ability to solve nonlinear problems. This study evaluated the efficiency of GPR for estimating pier scour depth using field scour data and compared the results with those from eight empirical equations. Of the empirical equations studied, the Froehlich empirical equation showed the best performance and was more accurate than the other experimental equations. When estimating the scour hole depth using dimensional parameters and GPR with a Pearson kernel function, the combination of input parameters of pier form factor, pier width, average particle size of bed sediment, and depth of stream provided the best-case scenario. The results represent the greatest efficiency and highest accuracy of GPR in comparison with empirical equations to estimate scour depth using sets of field data.
Original Article
Abstract
Direct measurement of soil hydraulic conductivity is time-consuming and expensive. Direct measurement of soil hydraulic properties can be replaced by simple measurement of properties such as soil texture and bulk density using transfer functions and an adaptive neuro fuzzy inference system (ANFIS). The ...
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Direct measurement of soil hydraulic conductivity is time-consuming and expensive. Direct measurement of soil hydraulic properties can be replaced by simple measurement of properties such as soil texture and bulk density using transfer functions and an adaptive neuro fuzzy inference system (ANFIS). The present study used ANFIS and neural network models to estimate saturated soil hydraulic conductivity. The model inputs included percentage of silt, clay, and sand. The architecture for this network contained 3 neurons in the input layer and 11 neurons in the hidden layer using the tangent sigmoid transfer function, and an output layer of neurons with a linear transfer function and 1000 iterations. In all networks, the learning rate and momentum was 0.3. The neuro fuzzy inference system had 27 rules, a Gaussian membership function was used for input data, and a hybrid method was used to optimize the ANFIS model. The root mean square error (mmd-1), percentage of relative error (ε), mean absolute error (cmd-1), coefficient of residual mass, efficiency, and coefficient of determination were used to evaluate the performance of the model. For the ANFIS model, these values were 0.032, 0.62%, 0.18, -0.0000023, 0.999, and 0.997, respectively. The values for the Levenberg-Marquardt training algorithm were 1.22, 1.44%, 1.21, -0.00015, 0.997, and 0.99, respectively. Performance evaluation of the models showed that the ANFIS model predicted soil hydraulic conductivity with greater accuracy than did the neural network and the results of this method were closer to actual measurement results.
Original Article
Abstract
Construction of weirs in river bends results in non-uniformity of water flow across a channel bend and can reduce the performance of intake structures on both sides of the river. It was hypothesized that more uniform distribution of flow across the bend can be achieved by changing the weir-crest profile ...
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Construction of weirs in river bends results in non-uniformity of water flow across a channel bend and can reduce the performance of intake structures on both sides of the river. It was hypothesized that more uniform distribution of flow across the bend can be achieved by changing the weir-crest profile from horizontal to sloping. The present study tested the performance of horizontal and sloping broad-crested weirs in a channel bend to achieve the most uniform distribution of unit flow rates across the river bend. The results indicate that horizontal crested weirs were sufficient at the entrance and exit of the bend, but within the bend reach, sloping crest weirs provided better convergence of the unit flow rates across the bend. It is recommended that the slope of the weir crest incline 2º to 5º toward the outer bank of the bend. The best location for the weir inside the bend is at that angular sections at 30°, 60°, and 45°, respectively. The flow equation over the weir was derived using mathematical and dimensional analysis. Discharge coefficient Cd was examined for free to submerged flow as a function of the position of the weir along the bend, geometry of the weir, upstream head water, and downstream tail water.
Original Article
Nader Gholi Ebrahimi; Azim Shirdeli; Hosna Shafaei
Abstract
Vegetation cover is a major environmental issue in rivers, streams, and irrigation channels. It constrains water discharge, increases sediment accumulation, and traps river loads. The present research experimentally determined the effects of vegetation coverage in an irrigation channel on its hydrological ...
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Vegetation cover is a major environmental issue in rivers, streams, and irrigation channels. It constrains water discharge, increases sediment accumulation, and traps river loads. The present research experimentally determined the effects of vegetation coverage in an irrigation channel on its hydrological characteristics. The rate of sediment trapping, sediment load from the exit point of the flume, Froude number, and bed slope were assumed as the experimental boundaries to test different types of vegetation coverage. A flume was constructed at the Soil Conservation and Watershed Management Institute that was 7 m in length and 25 cm in width. Testing was conducted at three vegetation densities (12%, 25%, and 50%) at water discharge rates of 4, 6, and 8 l.s-1. These conditions were repeated at bed slopes of 0.002, 0.004, and 0.006. A sediment load of 4000 g/min was added for each test. The highest sediment trap efficiency was reported at 50% vegetation coverage density and a Froude number of 0.015 with water discharge of 4 (l.s-1) and a bed slope of 0.002%. The results revealed an increase in sediment discharge as the Froude number decreased. The rate of sediment trapping increased as the vegetation density increased. An increase in load and a decrease in rate trap efficiency of vegetation were recorded for the steeper flume bed.
Original Article
Abstract
The protection of agricultural lands from sea water intrusion in countries with low coasts is of great importance. The present study investigated a soil failure mechanism to measure seepage force by numerical simulation of a laboratory coastal dike in FLAC software using the finite difference method. ...
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The protection of agricultural lands from sea water intrusion in countries with low coasts is of great importance. The present study investigated a soil failure mechanism to measure seepage force by numerical simulation of a laboratory coastal dike in FLAC software using the finite difference method. The results indicate that the FLAC model properly simulated soil behavior. The model predicted boiling with high accuracy and it was possible to predict the heaving mechanism after use of blanket and sheet piles seepage control measures using the stress analysis before implementing the final design. The results show that it is possible to decrease the hydraulic gradient and, thus, risk of boiling by lengthening the flow path. The safety factor was determined using FLAC without the need for manual calculation. Terzaghi equations indicate that the safety factor against boiling depends on several geotechnical parameters. The safety factor was determined in FLAC by considering the geotechnical parameters of friction angle, angle of dilation, type of material, and angle of friction between the soil and sheet pile.
Original Article
Abstract
A common problem in most irrigation systems during operation is pressure fluctuation. This issue is often neglected, but special measures must be considered to control and regulate it. The present research presents a method coded in MATLAB/mfile based on the use of variable speed pumps and pressure sensors ...
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A common problem in most irrigation systems during operation is pressure fluctuation. This issue is often neglected, but special measures must be considered to control and regulate it. The present research presents a method coded in MATLAB/mfile based on the use of variable speed pumps and pressure sensors installed at key points of the system to control and regulate pressure fluctuation. This method can predict and control causes of pressure fluctuations in the system and help to increase the efficiency of operation. The pressure sensors at key locations recorded pressure data over time. Dynamic planning using the data allowed decision-making to reduce fluctuations to continue pumping by transmitting information to the variable control drive through the program output. The results show that the use of this method in pumping stations equipped with variable speed pumps can reduce pressure fluctuations and optimize performance at the pumping station. The use of this method produced an RMSE index in the pressure fluctuation domain (±5% and ±10%) of 0.3 from a value of 0.9 before pressure control.
Original Article
REZA BAHRAMLOO; Nader Abbasi
Abstract
The current research examined the effect of air entrainment admixture (AEA) on the water absorption characteristics of concrete used in irrigation canal linings. Six concrete mixtures (treatments) were designed and constructed using at AEA values of 0%, 0.01%, and 0.03% of cement weight for cement contents ...
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The current research examined the effect of air entrainment admixture (AEA) on the water absorption characteristics of concrete used in irrigation canal linings. Six concrete mixtures (treatments) were designed and constructed using at AEA values of 0%, 0.01%, and 0.03% of cement weight for cement contents of 325 and 350 kg/m3. Testing was carried out on fresh and hardened concrete mixtures. The results showed that by increasing the AEA and cement content increased the slump, porosity, and water absorption of the fresh concrete and decreased its gravity. Increasing the AEA at both cement contents from 0.01% to 0.03%, decreased initial and final water absorption and water depth penetration of hardened concrete and increased capillary water absorption. The results confirm that the durability indices of the concrete lining improved significantly with the addition of 0.03% AEA.
Original Article
Abstract
In recirculating aquaculture systems, inlet flow current usually enters from the inner pyramid of the tank in the form of submerged jets. The hydraulics of jet alignment has an important effect on flow uniformity and solid removal efficiency. This paper examined experimental analysis of flow pattern ...
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In recirculating aquaculture systems, inlet flow current usually enters from the inner pyramid of the tank in the form of submerged jets. The hydraulics of jet alignment has an important effect on flow uniformity and solid removal efficiency. This paper examined experimental analysis of flow pattern in a cylindrical tank by placing a nozzles at each of three depths using four angle options (20°, 40°, 60°, and 80°) between the radius and jet alignments. The results indicate that angles of 40° and 60° created more uniform current in the tank. Changing the jet alignment from 20° to 80° decreased the number of local eddies and increased the average velocity in the tank. Comparison of inlet currents from one nozzle and from three nozzles showed that increasing the number of nozzles increased the jet velocity and the average velocity in the tank, but decreased the ratio of average velocity of the tank to external velocity of the nozzle jet. Paired comparisons of four options (average velocity for angles of 20° (op. 1), 40° (op. 2), 60° (op. 3), and 80° (op. 4)) show that options 2 and 3 had the strongest correlation. Shear stress monitoring in a round tank showed that shear stress increased at the stations of options 2 and 4. Increasing the ratio of h/H, increased the Froude number near the bed of the tank.
Original Article
sakineh soleymaninia
Abstract
Conventional concrete is widely used in hydraulic structures because of its availability. It is, however, possible to add compound nano-materials with very low weights to strengthen and increase the durability of concrete and, in this way, to increase its lifespan. The present research examined the effects ...
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Conventional concrete is widely used in hydraulic structures because of its availability. It is, however, possible to add compound nano-materials with very low weights to strengthen and increase the durability of concrete and, in this way, to increase its lifespan. The present research examined the effects of nano-silica and superplasticizer (resin-based plasticrete) additives on the abrasive strength of the concrete compared to conventional concrete. The test scenarios to create the desired concrete types used cement types 2 and 5. Nano-silica was added at 2%, 4%, 6%, 8%, and 10% of the weight of the cement. The super-plasticizer was tested at 0.5%, 0.8%, 1.1%, 1.4%, and 1.7%. All tests were conducted at the Niktaban-Dez laboratory over processing periods of 7, 28, and 42 d. A total of 60 tests for level of abrasion were done on the specimen. The results showed that by adding nano-silica and super-plasticizer to concrete made with cement types 2 and 5 initially increased and then decreased the abrasive strength of the concrete compared to conventional concrete. The mass loss with the addition of 6% and 8% nano-silica decreased and then increased. The minimum mass at 7, 28, and 42 d decreased 40%, 31% and 50% for type 5 cement and 27%, 32% and 50% for type 2 cement, respectively, over conventional concrete. The results showed that the abrasive strength with the optimum percentage of nano-silica and superplasticizer, respectively, was 6% and 0.8% for type 2 cement and 8% and 0.8% for type 5 cement.
