فهرست مطالب علی حسین زاده دلیر

Regarding the growing awareness of the environmental issues over the past decades, the main aspect of river engineering has been the environmental improvement of the rivers. River restoration refers to the environmental and ecological aspects of river engineering. New eco-friendly river restoration techniques such as vanes, deflectors, W-weir, U-weir, cross vane and J-hook vanes are generally designed and implemented in accordance with different hydraulic conditions to control the river bed, stabilize the banks, improve the river ecosystem conditions and to overcome the negative effects of the conventional structures on river natural functioning. These structures performance has been evaluated in many studies. Bank-attached vanes are one of the eco-friendly structures. In the present paper, the effect of the different geometry and permeability rates of these structures on turbulent flow pattern has been investigated.

Turbulent flows are simulated by solving the Navier-Stokes equations. FLUENT software and large eddy simulation (LES) mathematical model were used to solve the Navier-Stokes equations and simulate the turbulent flow field around bank-attached vanes in a straight channel. Smagorinsky-Lilly subgrid-scale model was used to model unclosed residual stress tensor (τ_ij) in the governing equations. It must be noted that subgrid-scale turbulence models in FLUENT employ the Boussinesq hypothesis to calculate subgrid-scale stresses (τ_kk). To simulate the flow field affected by different bank-attached vanes, boundary conditions, flow depth and approach flow velocity were determined. Streamwise measured and simulated free surface profiles around 30% permeable rectangular vane at different Y/L positions were compared to evaluate the numerical model accuracy. Numerical and experimental results agreed well since relative average error values were 4-5% in all cases. Furthermore, a mesh composed of approximately 150000 elements was considered as an optimum mesh for all created models to resolve flow characteristics. However, due to the different permeability rates, generating the optimum mesh for all cases it is not possible.

Velocity magnitude results around bank-attached vanes revealed the presence of two flow zones which are the main flow field, upstream and downstream separation region formed due to the local effects of the bank-attached vanes and channel constriction. These zones are separated by a fully turbulent and dynamic flow, named the detached shear layer. In general high velocity zones near the vanes tip region and channel bed effect the local scour hole characteristics, thus tip velocity and maximum velocity variations are investigated at the near bed horizontal plane. Moreover, parameters such as tip velocity, maximum velocity and flow separation angle are affected by the interaction of different eddies, varying geometry and permeability conditions. Results showed that tip velocity and maximum velocity ratios have declining trend with increasing permeability rate. Generally by increasing the permeability rate, bank-attached vanes do not have a significant effect on flow pattern. Bed shear stress is considered as one of the primary parameters that affect the main flow field and downstream separation zone, results showed that due to the local effects of the bank-attached vanes, channel constriction and interaction of the horseshoe vortices downstream of the simulated vanes, maximum bed shear stress values mainly occurred at X⁄L= 2.4 section. Furthermore, by increasing the permeability rate, maximum bed shear stress values shifted towards the channel centerline. In general, due to the triangular vanes cross-sectional opening (geometry), these structures effect on flow characteristics is smaller in comparison to the rectangular vanes.

The roughness of the open channels bed and the walls have a great impact on the hydraulic characteristics of the flow, and to perform the best management and control tasks, the change in the behaviour and characteristics of the flow in the presence of these roughness should be known well. Vegetation is one of the most important and common roughness, which have various types and characteristics. One of the most important characteristics is their degree of flexibility, which are usually divided into two general categories: rigid and flexible. From the past until now, researchers are always trying to predict the effect of the presence of vegetation on the flow path and to provide more accurate relationships for predicting different characteristics of the flow, including the flow velocity. The vegetation studied in this research is rigid and inflexible, and to bring the vegetation conditions close to their natural state, its height distribution is considered non-uniform and random.

Experiments were carried out using a rectangular flume with a length of 10 m, a width of 0.5 m and a depth of 0.6 m. At the downstream end of the flume, a rectangular weir with an adjustable angle was installed to adjust the flow height inside the channel and the vegetation submergence ratio. Vegetation models used in the experiments include stainless steel cylinders at three heights 3.5, 5 and 7 cm, which are used to simulate hard plant stems. During the experiments, the submergence ratio of the cylinders has been considered variable. The diameter of the cylinders is 5 mm. The distribution of the cylinders is staggered, where the longitudinal and lateral distances are the same, but the height distribution is completely random, and Mathematica software was used to generate random numbers to determine the location of each cylinder. The distance between the cylinders and, as a result, the vegetation density per unit area is variable and in total three different densities were considered for stems. The flow discharge varied between 5 and 60 lit/s and an ultrasonic flowmeter was used to measure it. Velocity measurement started from 4 m from the channel entrance. A 3D ultrasonic velocimeter (ADV) with a frequency of 25 Hz was used to measure the point velocity. The flow is assumed to be uniform and steady for all experiments.

The distance between the cylinders and, as a result, the vegetation density per unit area is variable and in total three different densities were considered for stems. The flow discharge varied between 5 and 60 lit/s and an ultrasonic flow meter was used to measure it. Velocity measurement started from 4 m from the channel entrance. A 3D ultrasonic velocimeter (ADV) with a frequency of 25 Hz was used to measure the point velocity. The flow is assumed to be uniform and steady for all experiments.Analytically using the momentum equation in the layers with vegetation and the logarithmic law in the layers without vegetation. The velocity profile is presented in this research, unlike the uniform distribution, has two inflection points whose position depends on the vegetation density. To determine the CD, a special plant Reynolds number (Re*) has been introduced, and as this Reynolds number increases, the drag coefficient decreases. An empirical relationship between CD and the effective parameters is presented. The effect of different dimensionless parameters that were extracted through dimensional analysis, was investigated on the flow velocity and the results show that with the increase in the flow Reynolds and the Froude numbers, the velocity increases in all the flow layers, but the change of these numbers has no effect on the position of the inflection points of the velocity profile. With the increase of the vegetation density, the flow velocity in the vegetation layers and the upper layer decreases and increases, respectively. By increasing the submergence ratio of the cylinders for a constant flow rate, the flow velocity decreases in all three layers, but the effect of the submergence increase on the flow velocity is different for the flow layers, so for example, with a 30% increase in the submergence ratio, the average velocity decrease in the vegetation layer is 10%, however, shows a decrease of 25% in the upper layer. As the results showed, with the change of vegetation conditions, many hydraulic properties of the flow changed, so this field still needs to be discussed. The present study was conducted on hard vegetation that has a random height distribution with regular intervals. In future studies, researchers can study natural vegetation with random intervals and bring their laboratory conditions closer to the conditions of the vegetation distribution in natural riverbeds.

Accurate knowledge of where jets hit downstream of dams helps designers a lot in locating plunging pools. The purpose of this study is to investigate experimentally and numerically the trajectory of pressurized jets through the gates and to determine their location downstream of the dam. Ansys - Fluent software was used for numerical simulation. The results showed that there is a significant difference between the experimental values and the values extracted from the jet projectile equations for predicting the path of the pressurized jets, and this discrepancy may be due to the effect of air resistance on flow. The existing jet trajectory equations don’t consider air resistance. To minimize this difference, the projectile equation was modified. Also, the effect of changing the diameter of the dam gate and the discharge on the point of impact of the pressurized jet on the ground surface was examined. By increasing the diameter of the dam outlet at a constant discharge, the location of impact of the impinging jet to the ground from the dam toe decreases, and with increasing discharge at a constant diameter of outlet, the place of impact of the pressurized jet to the ground from the toe of the dam increases. In addition, the numerical simulation results showed that the dynamic pressure as well as the velocity at the point of impingement of the jets on the river bed have the maximum value that should be considered in designs. The dynamic pressure as well as the velocity of the jet coming out of the gate hit the ground with an average increase of 145% and 242% relative to the end edge of the gate, respectively. In addition, the breaking length of the pressurized jet was investigated in this study, and it was found that the breaking length of the pressurized jet increases with the increase in the initial velocity of the water jet.

Pore water pressure, stress and settlement are the most important geotechnical parameters that must be constantly monitored during the construction of earth dams. Since measuring dam settlement directly at the time of dam construction requires cost and time, the development of artificial intelligence methods can be very effective. Most studies have been done in the field of modeling earth dams during construction with a numerical model; therefore the need for artificial intelligence modeling in this field seems to be necessary. Artificial intelligence models, including neural networks, are used for study and modeling many engineering sciences. Also, with the development of meta-heuristic algorithms, their combination with neural networks has become very wide-spreading due to more accurate results. So, The purpose of this study is to determine the most effective features in modeling settlement in the body of earthen dams at the time of construction as a case study (Kaboud-val dam) using the hybrid algorithm Dragonfly - artificial neural network in different points of the body of earthen dam at the time of construction. Therefore, in this research, new inputs in artificial intelligence modeling have been proposed for this purpose and their importance in different levels of installation has been investigated.

Kaboud-val Dam is located in Golestan province of Gorgan and around the city of Aliabad. This dam is homogeneous and has a filter and inclined drainage. In order to obtain the deformations of the body and the foundation of Kaboud-val dam, settlement plates have been installed in different sections of the body and its foundation during the construction. In this study, instrumental data related to the section of 19 Kaboud-val dam were used. Also, out of 17 pages, 4 pages named M1, M5, M9 and M13 (installed in the body and Kabudwal dam at levels 140, 152, 164 and 180 meter, respectively) have been used for modeling. By analyzing the data of section 19 pages, fill level (F), reservoir level (RL), dam construction time (T), fill rate (FR) and impounding rate (RV) for inlet and landing (P) on terms of (kp), was selected as the output of the hybrid model in the feature selection method. In this study, in order to select the best combination of input features in the artificial neural network, the dragonfly algorithm was used. Feature selection is a method of selecting a subset of related attributes (the best combination of them) that is relevant to a particular goal. The most important principle is to choose stable features and remove extra data. The combination of dragonfly algorithm with artificial neural network as DA-ANN is shown, Therefore, the dragonfly algorithm (DA) models a variety of different combinations of features with an artificial neural network and selects the best least error combination (RMSE) as the optimal artificial neural network model.

By performing a hybrid algorithm, sensitivity analysis and feature selection method, combining the four features on pages M1, M5,M9 and M13 with error values (RMSE) of 0.0023(kPa), 0.0024(kPa), 0.0026(kPa), respectively, and combining the three features on the M13 page with the value Error (RMSE) equal to 0.0035(kPa) was the best input combination. The three features of construction time, fill level and reservoir level as common features in all plates are the most effective features in modeling the settlement on selected plates. On plates mounted at higher levels, the modeling error increases, because during the test period and for plate M13 (with the highest mounting level), according to the statistical indices R^2, SI, NSE and NRMSE are equal to the values of 0.9998, 0.0062, 0.9998 and 0.0062 respectively, have poorer performance than other pages. The effect of reservoir level feature on the plates installed at higher levels due to the high sensitivity coefficient is more than other points and the fill level feature has the least effect on subsidence modeling.

The results are very important considering the cost of installing the measuring equipment and the significance of estimating the actual values in the future. The present study shows that the DA-ANN hybrid model is an important tool in predicting and selecting the best input combination for the intelligent model of the target variable of the settlement at the time of construction of earth dams. However, assessment of this model using the input data studied in different dams is necessary to ensure the application of these models in different conditions.

Accurate prediction of pore water pressure in the body of earth dams during construction is one of the most important factors in managing the stability of earth dams. In this study, using three different evolutionary neural network models including multilayer perceptron neural network with genetic algorithm, particle swarm optimization and Imperialist Competitive algorithm for estimating the pore water pressure in the body of Kabudwal earth dam at the time of construction, has been studied. Five features including fill level, construction time, reservoir level, impounding rate and fill speed during the 4-year statistical period were selected as the input of the hybrid model in piezometer EP19.7. The composition of the inputs was obtained using the feature selection method and the hybrid water cycle algorithm -artificial neural network. By performing hybrid algorithm and sensitivity analysis and feature selection method, fill level, construction time, reservoir level and dewatering speed were selected as the top four inputs, because the combination of these four features with MSE value of 1.1587 had the least error. In this study, artificial neural network weights are optimized to increase efficiency using the above three meta-heuristic algorithms. In general, according to statistical indicators, the results indicate acceptable accuracy of all three hybrid models. In terms of priority, the ANN-GA hybrid model with the highest accuracy and minimum error and values of , RMSE and MAE are equal to 0.9773, 0.0457 and 0.0399, respectively, is first priority and ANN-PSO and ANN-ICA hybrid models were given the next priorities, respectively.

Accurate prediction of pore water pressure in the body of earth dams during construction with accurate methods is one of the most important components in managing the stability of earth dams. The main objective of this research is to develop hybrid models based on fuzzy neural inference systems and meta-heuristic optimization algorithms. In this regard, the fuzzy neural inference system and optimizing meta-heuristic algorithms including genetic algorithms (GA), particle swarm optimization algorithm (PSO), differential evolution algorithm (DE), ant colony optimization algorithm (ACOR), harmony search algorithm (HS), imperialist competitive algorithm (ICA), firefly algorithm (FA), and grey wolf optimizer algorithm (GWO) were used to improve training system. Three features including fill level, dam construction time, and reservoir level (dewatering) obtained from the dam instrumentation were selected as the inputs of hybrid models. The results showed that the hybrid model of the genetic algorithm in the test period had the best performance compared to other optimization algorithms with values of R2, RMSE, NRMSE, and MAE equal to 0.9540, 0.0866, 0.1232, and 0.0345, respectively. Also, ANFIS-GA, ANFIS-PSO, ANFIS-ICA, and ANFIS-HS hybrid algorithms performed better than ANFIS-GWO, ANFIS-FA, ANFIS-ACORE, and ANFIS-DE in improving ANFIS network training and predicting pore water pressure in the body earthen dams at the time of construction.

The stress created in the soil significantly affects its engineering behavior. Changing its value during the construction of earthen dams causes volume change and shear strength, causing rupture, soil compaction and settlement in earthen dams. So measuring soil stresses of dams is essential that it is done by instrumentation installed. Artificial intelligence models such as artificial neural networks for modeling many engineering applications. Also by extending the meta-heuristic algorithms, combined with neural networks have become very popular due to more accurate results.

In this study, the cross-section 19 (cross-section of the middle part of the body and dam foundation) for the modeling of soil stress were used during the construction of the dam Kaboud-val. Also Kaboud-val dam instrumentation data (derived from Golestan Regional Water Co.) was used at the time of construction during the period of 4 years. Type and number of input data is the most important thing in modeling artificial intelligence. By examining data TPC19.1 cells in section 19 in Kaboud-val dam, embankment alignment (F), the water level of the reservoir (R), the construction of the dam (T), speed filling and dewatering speed was selected for input. The soil stress (P) in the body of the dam during construction, intelligent model was selected for output. This process is most effective in a subset of features from the set of input features according to the least error, selected and additional features will be removed. In this research, a meta-algorithm (artificial neural network (NNA) algorithm) is combined with an artificial neural network (ANN) that has the ability to predict complex and nonlinear relationships and extracts effective features for modeling soil stress with appropriate accuracy. In this study, the most effective features in soil stress modeling were determined in a case study (Kaboud-val Dam) using the NNA-ANN hybrid algorithm and a comparison was made between the results of the hybrid model and the numerical model. Five features include reservoir level, fill level, dam construction time, impounding velocity and fill velocity was selected for the input.

Using hybrid algorithm and feature selection method, a combination of three features, including reservoir level, fill level, dam construction time (with RMSE equal to 0.5024) were the most effective features in modeling soil stress in the selected cell. The results showed that the hybrid model in Kaboud-val Dam (with values of R^2, RMSE, MAE and NS equal to 0.9943, 2.5653, 1.9973 and 0.9999, respectively) has better performance in modeling soil stress than the numerical model. (With values of R^2, RMSE, MAE and NS are equal to 0.9625, 26.2567, 16.6725 and 0.9772, respectively). The results showed that the reduction in the input features to reduce the time and cost reduction is more economical and more effective. Because with the increase in the number of features in the hybrid model, the increase in modeling accuracy did not occur. Sensitivity analysis showed that the dam construction time and fill level, of the highest sensitivity factor, the most important feature of the model is the total stress in cells. Modeling with the mentioned features, in another dam with a new construction site and new geotechnical specifications (Masjed Soleiman Dam) showed that the use of artificial intelligence model according to statistical indicators has more accurate answers than the numerical model.

The results showed that the use of artificial intelligence methods in the design and initial estimates of soil stress parameters in earthen dams instead of using numerical methods has high reliability and accuracy. The combination of input data in the hybrid model under study is suitable for Kaboud-val dam and Masjed Soleiman dam and the appropriate combination should be used for each construction site. By completing the number of data in different sections of the dam and the number of construction sites in areas with similar climate and geotechnical conditions, a design software can be obtained to predict the amount of soil stress during construction in the body and foundations of earth dams.

One of the basic measures in managing the stability of earth dams is to accurately estimate the amount of pore water pressure in the body of the dam during and after its construction. In this study, three different models of artificial neural network (ANN), adaptive neural-fuzzy inference system (ANFIS) and gene expression programming (GEP) to estimate the pore water pressure in the body of Kabudwal earthen dams at the time of construction have been studied and compared. Five features including fill level, construction time, reservoir level, impounding rate and fill speed have been used during the 4-year statistical period as input of models in 4 piezometers installed in the dam body. The first three features were the most effective inputs according to the cross-correlation function. In this study, the results obtained from artificial neural network (ANN) in two piezometers according to statistical indicators, provided more accurate answers than gene expression programming (GEP) and ANFIS, but in the other two piezometers it was the opposite. Also, ANFIS and GEP models provided more accurate answers in piezometers that had higher data scatter than ANN model. Finally, based on the GEP model, mathematical relationships between input features and output variables were extracted.

In this study, flow characteristics and pressure parameters of hydraulic jumps has been investigated in a laboratory flume. The results for different incident Froude numbers (Fr1), at the downstream of an Ogee spillway on the typified USBR II stilling basin bed were compared with the USBR type I basins. Dimensions of the Ogee spillway and stilling basin were designed according to the USBR criteria. The pressure data of the points on the basin bed were recorded using pressure transmitters with 20 Hz frequency. Experimental parameters including flow depth and velocity at the start and end points of free jumps (Y1, Y2, V1 and V2), and submerged jumps (Y3, Yt, V3 and Vt) were measured. In the present study, dimensionless parameters of energy dissipation efficiency (εt), mean pressure head (Ψ*X), standard deviation of pressure fluctuations (Φ*X), maximum positive pressure fluctuation coefficient (CP+), maximum negative pressure fluctuation coefficient (CP‒), total pressure fluctuation coefficient (CP) and skewness coefficient (Ad) were investigated. Pressure parameters are dependent on Fr1, the point position (Γ*X), and the submergence degree (S). The results showed that by reducing the values of Fr1, parameter εt decreases. The parameter Φ*X max in the USBR type II basin decreases around 30% compared to the type I basins in free jumps. The reduction of Φ*X max values in the submerged jump with S=1.4 is about 29% than free jumps. The values of CP+max and |CP‒|max coefficients in the submerged jump with S=1.4 in comparison with free jumps decreases about 15% and 17%, respectively.

The scour has been studied in hydraulic science for many years, due to its complexity and lack of proper relationship, it has been the attention of hydraulic scientists. Hydraulic structures situated as an obstacle in front of water flow that changed the flow pattern in their vicinity and causing the local scour around the structure. There are various methods to reduce local scour around the pier. In this research, sacrificial pile and collar were used to reduce the local scour around inclined pier group. The results show that using of the sacrificial pile in front of the inclined pier group, the effect of the inclined pier angle on the reduction of the scour is lower. So that difference between the percentage of scour reduction for the first and second inclined piers in the angle of 5 and 15 degrees is zero and in vertical pier is 1.4%. The use of three collars with a diameter of 4b in pier group with the distance of 4b between piers and presence of sacrificial pile in front of the first inclined pier in distance of 3b compared to 2b show a greater scour depth reduction in front of the piers. In the numerical model, the use of inclined pier group with the distance of 3b between piers and sacrificial pile with distance of 2b shows lower turbulence intensity compared to distances of b and 3b.

In this study, different components that affect energy dissipation on flow over gabion-stepped spillways were investigated using physical models, and comparisons were made with the other studies. Flow over gabion spillway was conducted in both through flow and overflow simultaneously. The discharge is in the range of 5 to 65 liters per second.  Uniform particles with three medium diameters of 10, 25, and 40 mm were used. The height and width of the physical models were 60 and 40 cm, respectively, with 3 steps and the downstream slope of weirs was 1:1, 1:2, and 1:3 (V: H). Tow end sills including rectangular and inclined shapes were used. The results showed that the effect of end sills in gabion-stepped weirs with lower slope is more than that of weirs comprising higher slope. The effect of the end sills on the energy dissipation in the weir for d50=40 mm and S=1:2 is about 10% more than the weir with d50=10 mm and S=1:1. In weir including d50=10 mm and S=1:2 is about 30 to 35 percent more than the weir with d50=10 mm and S=1:1. Therefore, the existence of end sills in the weirs with the body of materials of d50=10 and 40 mm have the highest and the least effects on the energy dissipation. On the other hand, the effect of the rectangular end sill on the energy loss is about 3-4% more than that the effect of the triangular end sill.

In this study, the ability of WCA-ANN hybrid algorithm to model the pore water pressure coefficient in the body of Kabudwal dam at the time of construction was investigated and the effective features were identified. Therefore, five features including fill level, time, reservoir level, dewatering rate and fill speed during the 4-year statistical period were selected as the input of the model. By running the hybrid algorithm and feature selection method, the two features of fill level and time at points RU19.1  and   RU19.2 have the greatest impact on modeling the pore water pressure coefficient. In addition to the above two features, in the points of the middle axis , the features of fill speed and reservoir level with error value (MSE) equal to 0.00006 and in points close to the dam reservoir, dewatering level and dewatering rate with error value equal to 0.00004 are effective in modeling the pore water pressure coefficient. The results showed that at points close to the dam axis, the fill level and at points farther from the middle axis construction time (with high sensitivity coefficient) was recognized as the most important features in modeling the pore water pressure coefficient with artificial intelligence models.

Hydraulic structures situated as an obstacle in front of water flow that changed the flow pattern in their vicinity and causing the local scour around the structure. The scour around the bridge pier is one of the most important phenomena in sediment hydraulics, which creates a hole around the pier and undermines its stability. Different methods have been proposed to prevent or reduce the local scour. In this study, the effects of collars, nanoclay materials and angle of piers have been studied in pier group. The results show that for the pier with the angle of 15 degree was observed the greatest decrease in the depth of the scour hole. Studies show that in the group pier with inclination angle of 15 degrees, there was 14 percent scour hole reduction and with presence of a collar the reduction of scour hole was 86 percent. Also, by using nanoclay materials, the depth of the scour hole in the without collar condition was reduced by 18.5%.

One of the most important issues in river engineering science is the river training in the bend of the rivers. Training operations are carried out to prevent changing the curvature in the bend of the rivers, protecting the external bank against erosion, and also controlling sedimentation in vicinity of the internal bank of the rivers. The use of submerged vanes is one of the practical methods used to train the rivers, stabilize the bank of the rivers and protect it against erosion. Submerged vanes are guidance stream structures that are installed at the river bed with an angle to the main flow and designed to adjacent flow pattern improvement. In this study, after dimensional analyzing and determining the effective dimensionless parameters, submerged vanes are placed in three lengths and three different angles in a channel with a mild sinuosity curvature and their performance was compared with each other. The results showed that by increasing the length and distance between submerged vanes in a constant Froude number, the maximum scour depths, increases, so that the maximum scour depth was observed for first vane in the angle of 110 degree and length of 2.66 H0. The most suitable and destructive angles for the establishment of submerged vanes are equal to 140 degree and 110 degree, respectively.

Open channel junctions are so important in water conveyance networks. As a result, the researchers have been focusing on study of flow characteristics in these parts of water systems. Numerical simulation allows us to achieve the answer for engineering problems without encountering the experimental difficulty and with minimum cost. The aim of this study was, developing a 1D analytical model for simulating open channel junctions base on continuity, energy and momentum equations and some simple assumptions and comparing the experimental results in order to validation of analytical results. In experiments, side slope of main channel was 45 and 90 degrees. The studied variables were the ratio of depth at the junction. Investigation of results showed that increase of Froude number and inlet discharge ratio would lead to increase of turbulence which would decrease precision of analytical model. Also the increase of side slope of main channel caused less turbulence and more precision of the analytical model. In analytical model maximum reported error was about 15% for angle of 90 degrees, with relatively high discharge and depth in main inlet channel and minimum reported error was about 5% for angle of 45 degrees, with relatively low discharge and depth in main outlet channel

Gabion stepped weir is a simple hydraulic and environment friendly structure that can be used to dissipate flow energy in different dams or to control downstream erosion of various structures. Most researches have been related to concrete and rigid stepped spillways, so studies on gabion stepped weirs are very small. In this research using the experimental method and physical model various components that affect the energy loss in gabion stepped weirs have been studied and comparisons with other studies by researchers have also been made. The flow passes in gabion stepped weir was carried out both in overflow and inflow (both simultaneously) and the amount of energy dissipation along the structure was calculated based on the energy relation. In this study, completely uniform particles with three diameters ( ) of 10, 25 and 40 mm were used. The height and width of physical models made of gabion stepped weirs were 60 cm and 40 cm respectively, with stairs of 3, 6 and 12 and height of stairs 5, 10 and 20 cm and the slope of the weirs are 1:1, 1:2 and 1:3 (2 and 3 horizontals, 1 vertical). In the gabion stepped weirs, the downward slope of the weir has a negligible impact on the energy dissipation. As the number of steps increases (for constant ), the energy loss decreases. The average diameter of the particles of 10 mm for and the average diameter of the particles of 40 mm for has the highest of relative energy loss.

Every year heavy rainfalls cause many slope failures. In these rainfalls, the groundwater table increases that cause in increasing of pore water pressure and reduction of slope stability. Using of horizontal drains is an effective and economic method to control the slope stability in this condition. The purpose of this study is to investigate the performance of horizontal drains in increasing slope stability. For this purpose, the SEEP/W and SLOPE/W (subgroups of Geo-Studio software) were implemented. Results showed that increasing in the length, thickness, and number of horizontal drains causes increasing in slope stability during the heavy rainfalls and keep the slope more stable. In addition, installation of drains in the down part of slope is more effective than in the middle or top part of the slope. Relative drain length equal to 0.4 is proper for improving of slope stability. Increasing of drain thickness have more positive effect on slope stability than the drain length.

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.

Side weirs are hydraulic structures installing on the side walls of the channels to divert excess water of main channel. Labyrinth weirs are broken in their plans; so, they have more effective length and in some conditions have more discharge coefficient than that of simple ones. In this research, the effects of piles with different arrangements on discharge coefficient of semi-circular labyrinth side weir have been studied. The experiments were carried out in a rectangular channel with subcritical flow with Froude number range equal to 0.1-0.37. Three diameters were considered for semi-circular labyrinth side weirs with constant height. The piles used in the study were cylindrical and the same height of the side weir. The number of piles varied from 1 to 3, and fourteen arrangements were considered for them. First of all, the effects of dimensionless parameters, obtained from the Buckingham method, on side weir discharge coefficient were studied and then a relationship, with acceptable accuracy, between these parameters was obtained to predict the discharge coefficient of semi-circular labyrinth side weir with piles.. The results,  compared with semi-circular labyrinth side weir without piles, showed that semi-circular labyrinth side weir with arrangements of piles have higher discharge coefficient. In fact, piles proved an improvement in the performance of semi-circular side weirs, so that within the range of the studied Froude number, the discharge coefficient faced an increase up to 15% and specific energy changes faced a decrease up to 34%. The most increase in discharge coefficient and the most decrease in specific energy changes occurd when three piles were installed at the downstream end of weirs.

In the present research, height and velocity of shock waves in contractions of open-channel with trapezoidal and rectangular sections was investigated using experimental models. For this purpose, length of transition (0.5m), convergence ratio (1/2, 1/3 and 1/4) and side slope angle (45o, 60o, 70o and 90o) were considered as geometric variables of the experiments. Also 4 Froude number was assumed as a hydraulic variable of the experiments in the range of 3.25-9.23. Analysis of Free surface & velocity profiles of shock waves showed that in general, the increasing of side slope angle of the transition wall, reduction of convergence ratio, and increasing of Froude number have a direct relationship with the increasing height and velocity of shock waves. The results showed that in the contraction with trapezoidal section with the convergence ratio (1/2) and side slope angle (45o, 60o and 70o) compared with rectangular cross-section, on average maximum height of shock waves respectively decreased to: 59.34, 44.27 and 24.04. In the same condition the maximum velocity of shock waves respectively decreased to: 37.51, 25.23 and 14.67. As Executive channels mainly with a trapezoidal cross-section are building and operating, so the findings of this study can be very useful for design engineers.

In present study, the effect of different cross-sections of bridge piers on reducing the bed erosion and the bed shear stress was experimentally and numerically evaluated. In experimental study, the bed erosion and the percentage of its resuction was calculated;also numerically, the flow around pier models was simulated three dimensionally, and the effect of each cross-section on reduction of bed shear stress was investigated. To determine the efficiency of suggested models, the circular model was selected as the reference model and the decreasing of maximum shear stresses in each model was compared with the decreased scour depth. Comparison of the velocity and water free surface profiles was conducted for verification of turbulence models and results showed that with model, more accuracy can be obtained. Among the presented models, the A2 model with decreasing scouring depth of 72 percent as copared to the refference model, was found to be best and most effective model. Also the B2 model lead to 8 percent reduction in scouring depth and can be suggested as a model that has the least effect on scouring. The D model causes the scouring depth increase by 7 percent relative to the reference model. Comparison of the numerical and experimental results was another objective of this study due to the complexities of experimental researches. The results showed that there are direct relationship between the bed shear stress and the equilibrium scour depths.

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.

Study of water depth variations in downstream of channel junctions, in order to get suitable situations in intakes, is necessary. In this research, analytical model for investigation of different hydraulic and geometrical factors on water depth variations at downstream of the four-branch junction with subcritical flow were presented and results were compared with experimental data. The results showed that as inlet discharge ratio, ratio of height of weir at the end of lateral channel to the height of weir at end of main channel , bed level of lateral channels and the height of outlet weirs increased, water depth in main outlet channel increased too. Increase of Froude number in the main inlet channel caused decrease of the water depth in the main outlet channel. As change of junction angle, quantity of the discharge turned into the main outlet channel changed which affected the water depth so that maximum water depth occurred for angle of 90 degrees and decreased as junction angle decreased. Comparison of the results for analytical and experimental models about flow depth in downstream channel showed a good agreement so that maximum error was less than 10%.
Due to the importance of this phenomenon, researchers around the world have focused and lots of experimental and analytical studies have been carried out in this case. Researches were mostly about three-branch junctions and there was less study about four-branch junctions. Teylor (1994) was the first person studied open channel flow by analytical model and simulated water depth into lateral channel. Rivie’re et al. (2011) studied flow in four-branch channel experimentally and extended one-dimensional model for flow distribution and compared experimental results with analytical. In this research, analytical model for investigation of different hydraulic and geometrical factors on water depth variations at downstream of the four-branch junction with subcritical flow were presented and results were compared with experimental data. The suggested analytical model was one-dimensional and base on mass, energy and momentum conservation laws with some hypothesis such as: Inlet and outlet flows were considered as uniform; Flow was vertically uniform; Pressure was hydrostatic in channels; Energy and momentum coefficients were considered 1; Head losses due to friction of wall and bed, also, due to turbulence and shear stress were ignored. Considering variables, in order to solve problem, 6 equations were needed: two energy equations, two momentum and two stage-discharge equations. For solving equation systems (6 equations and 6 unknown variables) MATLAB 2011 was used. Experimental study was carried out in hydraulic lab of Tabriz University, Iran. Length of the main channel was 8.4 m and the lateral channel was 2.4 m. Width and height of the both channels was 0.4m and 0.5m, respectively. The slope of the channels was zero. In order to measure of discharge weirs used, which were installed at first and end of the channel. In the experiments, height of weirs considered 15, 17.5, 20, 22.5, 25 cm and the discharge ratio was 0.2, 0.4, 0.6, 0.8 and 1.
Results showed that as increasing of discharge ratio, water depth in outlet main channel increased. When inlet discharge ratio increased, the flow that deviated into the outlet main channel increased that leads to increase of water depth. Amount of the error in prediction of the water depth by analytical models was less than 10%. Increase of the height of the weirs at the end of the outlet channels caused increase of water depth. The error of the predicted water depth also was less than 10%. As increasing , deviated flow into the outlet lateral channel decreased while the deviated flow into the outlet main channel increased and therefore the water depth increased. The amount of the error for prediction of water depth by analytical was about 5%. Expanding the bed channel of the outlet lateral caused decrease of deviated flow into the outlet lateral channel that leads to increase of the deviated flow into outlet main channel and increase of water depth. Also, increasing the Froude number of the outlet main channel, flow velocity increased and water depth decreased. Maximum water depth in outlet main channel observed for the angle of 90 degrees and minimum water depth happened when the angle of the channel junctions was 60 degrees.

The rough in flood plains in a compound canal and its impact on hydraulic parameters such as the shear stress and their estimation are one of the problems that have attracted the attention of engineers. The purpose of this study is determining of the shear stress distribution in the walls and bed of the semi-compound channel and the variation of the velocity profile for smooth and rough bed conditions. Four types of rigid wood roughness were used to investigate the effect of these parameters. These roughness elements were arranged with zigzag state with two distances of 4k and 8k in the floodplain. A total of 90 experiments have been conducted, with a flow rate in the range of 21.66-54.4 liters per second. A Preston tube with an external diameter of 3 mm that equipped with dynamic pressure sensors was used to compute the shear stress. In order to convert the difference between the static and dynamic pressure measured by the Preston tube to the shear stress values, the Patel calibration curve was used. The results were showed that the zigzag arrangement with the density of 4k, the shear stress is reduced due to the high roughness density and the greater area of ​​roughness. In a rough bed, the shear stress in flood plain was significantly higher than smooth bed, and the stress distribution is such that it has descending trend from the main channel toward the wall of the floodplain. The shear stress increase for roughness with a spacing of 8k is 27% to 38% higher than the similar hydraulic condition in a smooth bed. By increasing the flow velocity for arrangements of b2 and d2, the shear stress of the bed has decreased about 5% to 12% for discharges Q3 to Q5 compared to the roughness with a spacing of 8k.

Contractions are widely used in channels with supercritical flow, such as water conveyance systems from dams to tunnel spillways, chutes and flood delivery conduits. Technically, production and development of the mentioned waves are undesirable due to water depth increase because of several times increasing of inflow water depth, its spread at a wide range in downstream of channel and water surface roughness. Any weak design of channels under supercritical condition can cause to scour bed and wall the channel, damage to equipment in the flow direction, raising maintenance costs and reduce water conveyance efficiency. In the present research, the formation of shock waves in contractions of open-channel with trapezoidal sections was investigated using experimental and numerical models. The length of transition walls (0.5 and 1m) and angle of side walls (35º, 45º, 60º and 70º) were intended as geometric variables. In different point of shock waves the values of height and instantaneously velocity were measured in the contractions for Froude number and convergence ratio 7.26 and 0.5 respectively. In this research Flow-3D software and in order to simulate turbulent flow, the k-ε RNG model was used. Experimental results showed that increasing the angle of side walls and reducing the length of transition walls caused increment of the shock waves height and velocity. The average relative errors of calculation of shock waves height for different angles: 35º-70º and length of transition walls: 0.5m and 1m were respectively in the range of 4.29-5.06 and 2.28-3.14 percent. Also, the average relative errors of calculation of shock waves velocity for mentioned models were respectively in the range of 3-4.90 and 5.68-7.63 percent.