نشریه تحقیقات مهندسی سازه های آبیاری و زهکشی
سال بیستم شماره 75 (تابستان 1398)

The study of hydraulic condition around the rivers confluence and open-channel is important in various aspects, including erosion, sedimentation and environmental considerations. One of the most important characteristics in the confluences is dimensions of separation zone. This zone immediately develops in the lower corner of the junction, as flow entrance of the lateral channel into the main channel. In this research, side slope effects of the main channel on dimensions of flow separation zone was studied. Experiments were conducted with four discharge ratios, four downstream Froude numbers and four side slope angles of 45°, 60°, 75° and 90°. Results showed that the separation zone enlarges by decreasing of side slope angle of the main channel wall. The results showed that on average, and for side slopes angels of 45°, 60° and 75°, the length of separation zone was increased 55.3%, 30.3% and 15.5% respectively in comparison of the vertical wall. The mentioned values were achieved 33.8%, 22.7% and 10.8% respectively, for the width of separation zone. On the other hand, the dimensions of separation zone increased by decreasing of the downstream Froude number and increasing of the discharge ratio. Also, increasing of side slope angle was accompanied with increment of separation zone shape index. For side slope angles of 45°, 60°, 75° and 90°, values of this index were obtained 0.144, 0.147, 0.150 and 0.156, respectively. Moreover, a regression equation was developed using dimensionless parameters for prediction of separation zone dimensions; it was compared with the equations presented by other researchers, for side slope angle of 90o.

Distribution of required water for irrigation purposes in agricultural farms is one of the main objectives of irrigation networks construction. In this research, a PID controller was used to improve the operational capability of the main canal of Alborz Irrigation Network. For this purpose, a PID controller was developed in upstream and downstream directions in FORTRAN language and was combined with a ICSS hydrodynamic model designed in order to simulate the hydraulic and hydrological conditions and to operate water transfer systems. The PID controller can minimize errors between the actual and target depths. The operation option was considered in order to investigate the ability of the controller in keeping the level of the water constant at the time of the simultaneous decrease and increase of water flow entering the canal and the need of pond canals. Two scenarios were used to compare the mentioned controllers. Results indicated that the water surface error in downstream controller was lower than that in upstream controller. In downstream controller, the water level error at the beginning of opeartion, compared to the status quo, was 87.5%, 87%, and 87% for each structure, and within 18 hours, 97%, 99.5%, and 99.7% improvement rates were obtained. Furthermore, in upstream controller, the water level error, compared to the status quo, gained some improvement the rate of which differed according to the time; in other words, at the beginning of simulation, it was 75%, 93%, and 92%, within 12 hours was 27%, 97%, and 96%, and within 18 hours was 77%, 94%, and 98% Moreover, the system response time in the upstream controller was less than that in downstream controller. A comparison of existing conditions results with those of application of controllers proved acceptable ability of the controller designed to control the water level.

Hydraulic engineering studies need to know the sizes of surface sediments exposed to flow. The conventional ways, manual measurement methods such as performing gradation tests (sieve analysis) in a laboratory, face many problems in determining the sizes of sediments. An algorithm has been developed to facilitate problems. By providing a number of images of the bed materials during field surveys and providing land use information, this algorithm can help accelerating processing and increasing the accuracy of modeling. To verify the accuracy and precision of this algorithm, versus the conventional soil gradation method, four different digital cameras (with 6, 10, 12.1, 14 megapixels resolution) and two square-frames (0.5 and 1 meter in size) used for imaging and sampling bed materials, in dry and under low water flow conditions, in a distance of 5 km in Sirch River, north east of Kerman. The results showed that cameras with high resolution had the least error in estimating the average diameters of materials in dry beds. However, due to the uniformity of the bed surface particles, the performance of cameras with 6 and 14 megapixels was also acceptable, so that the maximum difference in the average diameter estimation was less than 12%. The cameras with 12.1 and 10-megapixels had lowest error in estimation the maximum particle's diameters, respectively. Furthermore, calculations carried out in the wet bed surface indicated that the results of images processing obtained from the camera with a low resolution, 6 megapixels, differ greatly from what had been obtained by other cameras, especially in distribution of the gradation curve and statistical characteristics of the particles. A survey on the statistical characteristics of the bed surface materials distribution showed that the average diameter, maximum diameter and deviation of the particles obtained from the camera with a resolution of 10 megapixels were greater than those obtained by other cameras. In a general conclusion, it can be stated that there is a direct relationship between these parameters: the image dimensions (frame), the resolution of the camera and its distance from the stream bed, in a way that by reducing the resolution of the camera in a fixed frame, the camera's distance from the stream bed should be increased, and vice versa. Based on the results in the streams with fairly uniform grain distribution, any camera can be used. But in streams that have a coarse-grained or fine-grained bed, it's better to use low and high resolution cameras, respectively.

The shape of the artificial channel sections and their optimal design by artificial intelligence methods can have significant effects on lowering the costs of constructions. In this study, an artificial channel with inverse cycloid and its optimal design by bat algorithm was introduced for the first time. Two schemes of sections were proposed: inverse cycloid without horizontal bed and inverse cycloid with horizontal bed. For optimal designing of proposed section, two scenarios were defined: channel with fixed freeboard and channel with variable freeboard. In both scenarios, Manning equation was used as a constraint and Horton equation was used for considering equivalent roughness. Based on sensitivity analysis, optimal parameters of the proposed algorithm were determined. Bat algorithm has been implemented randomly for each section and for each scenario for fifteen times, and coefficient of variation and speed of convergence were estimated. To find out the accuracy of bat algorithm in the global optimum determination, a comparison between solutions of bat algorithm and lingo software was made. Eventually, results from optimal design of proposed sections were compared with trapezoidal channel, parabolic with horizontal bed channel, ellipsoid channel, and general ellipsoid channel. Results from random runs of bat algorithm indicated that coefficient of variation for defined sections and scenarios were about 0.0002 to 0.0013. Convergence curves showed that the algorithm was convergence for all sections and scenarios in 1000 repetition. Findings of bat algorithm and lingo software also demonstrated high accuracy of mentioned algorithm in determination of global optimum. Furthermore, using proposed sections, compared with other common sections, led to 34.7 percent decrease in construction costs. Among sections and scenarios investigated here, the inverse cycloid under second scenario was found more economical, up to 17.15 percent.

In this research, the effects of a network of holes in the bottom of the stilling basin on the main properties of the hydraulic jump, such as the sequent depths ratio and the jump length, have been studied. First, by mathematical analysis and expansion of  the momentum equation, an equation for the direct calculation of sequent depths ratio was obtained while flow rate in the channel decreased. Using a laboratory flume , equipped with a network of valves under the bed, a series of experiments were conducted in order to study the behavior and characteristics of hydraulic jump, the results of which were compared with the results obtained from classical hydraulic jump on a smooth bed. The Froude number range in this research was between 5.3 and 7.4 and the ratio of the remaining flow at downstream to incoming flow to the channel was between 0.98 to 0.995. Results showed that reducing the flow rate up to two percent in the channel caused decreasing sequent depths ratio by 19 and 12 percent, compared to classical jump and analytical equation, respectively; the jump length decreased by 29 percent, compared to the classical jump.

Labyrinth weirs can be used to increase outlet capacity for a given spillway crest elevation and length or to increase storage by raising the crest while maintaining spillway capacity. Downstream scour dimensions of spillway are important parameters in designing of this structures. By combining the spillway and the gate, two major problems of sedimentation on upstream of spillway and the accumulation of waste materials can be solved. In this study, totally 12 experiments were carried out in 3 different discharges, 10, 15 and 20 liters per second. In this study overflow and flow simultaneously from top of weir and gate for two linear and labyrinth spillway were explored. A layer sand with d50=1 mm and thickness of 15 cm were covered at downstream apron to make a mobile bed. Results showed that by increasing the particle Froude for a constant depth, the maximum scour depth and scour hole length increased. Also it was found that when the flow passed through the spillway and gate simultaneously, in both labyrinth and linear spillway, the maximum scour depth and scour hole length increased with respect to discharge. Transverse profiles at the maximum scour depth also showed that there was a relative symmetry in the case of a linear spillway without a gate, and in this case the bottom profile could be considered as two-dimensional. The maximum scour depth and scour hole length increased with increasing discharge, and its magnitude in labyrinth spillways, was less than that in linear spillways.

Intake Modules are structures that deliver relatively constant discharge irrespective of water surface fluctuations. One of these modules is baffle sluice modules for which various theoretical methods have been proposed so far for determining their dimensions. Determining the best theoretical approach requires experimental studies. In this regard experimentations have been carried out only for low capacities. Therefore, numerical methods can be used to identify design criteria of baffle modules in higher capacities. But because of the scale effect on experimental models such as weir, the use of these models in higher capacities requires time and cost. Also, considering the type of design of the baffle modules, determination of the sensitivity of baffle height in determining the share of flow over the baffles and the rate of discharge of each duct is very important, which is not feasible in Experimental models. In this research aims to evaluate the application of three-dimensional numerical models in simulation of flow in baffle modules for reproduction of observational data, determination of the share of flow over the baffles, the rate of discharge of each parallel duct and the use of stage-discharge equations. The result of Flow-3D software indicated that very good concurrence exists between the numerical model output and the observed data for low discharge and this software is applicable to determination of design criteria for the modules for high capacities, determination of the share of flow over the baffles, the rate of discharge of each parallel duct and the use of stage-discharge equations. This indicated the capability of such mean to substitute experimental test or to decrease their use for special cases with an average error of about 1.7% for 14 l/s, 3.97% for 10 l/s, 5.22% for 7 l/s and 7.94% for 4 l/s.

The necessity of drainage and improvement of soil resistance parameters are unavoidable in the most mineral and geotechnical projects. Therefore, electrokinetic geosynthetic, as a fundamental technology, is capable of increasing the stability and stabilization of fine-grained soils and derive from the combination of electrokinetic performance and electroosmosis flow along with the application of geosynthetics. In this study, to enhance and improve the electrokinetic geosynthetic process, an electrode based on geotextile by chemical polymerization was developed. For this purpose, non-conductive fibers of geotextile sheet was converted to the conductive fibers by coating with a pyrrole conductive polymer (using two types of oxidants) and aniline conductive polymer, along with the adding four different types of nanoparticles. Then, to evaluate the efficiency of the geosynthetic electrode comparing to the copper electrode, a physical model was designed and filled by saturated kaolinite clay and drained by the electroosmosis process. According to the results, coating with Pyrrole polymer was only in the form of a layer around the geotextile fiber and did not obstruct the porosity of the fiber. Therefore, this fiber, after the coating, has the capability of simultaneously applying as a filter and electrode, and after the completion of the electrokinetic process, it can remain as a filter in the soil without removing. In this study, the results demonstrated that the geosynthetic electrode with a minimum measured, 670 ohms, at a maximum pressure, 0.083 ( ), by applying electroosmosis process was capable of draining 43 milliliters of water, which was only 14 percent lower compared to the copper electrode and similar conditions.