اکرم عباسپور

In the present study, the trajectory of free falling jets is investigated numerically and experimentally. The results showed that the domain of free falling jet in laboratory work is less than its calculated value using the projectile equations and the sample simulated using Ansys-Fluent software is due to air resistance. The equations of the projectile prediction and the simulated path in Ansys-Fluent have an error of 20.6% and 25.5%, respectively, compared to the laboratory data. Since none of the previously presented equations for calculating the path of falling jets were obtained using laboratory results and did not consider air resistance, therefore, they have errors in calculating the path of falling jets. In the present study, two equations have been presented to calculate the path of the free falling jet, which have a relative error of 3.02% and 9.14%, respectively. These relationships significantly reduce the error of calculating the path of the free-falling jet. By reducing the outlet cross section of the free falling jet and increasing the head passing through the dam spillway, the free falling jet reaches the ground at a greater distance from the dam body. Since none of the equations presented for calculating the trajectory of jets have been obtained using laboratory results and have not considered air resistance, so they have an average error of 21% in estimation of trajectory jet. In the present study,

Labyrinth weirs are often a desirable design option to regulate upstream water elevations and increase flow capacity and the gate structures have some advantages including passing the floating substances and the sediments in using combined weir-gate structure. But, it can be difficult to design due to the complex flow characteristics of a labyrinth weir-gate. A labyrinth weir could be described as a continuous and broken weir plan in a trapezoidal or triangular form. Thus, for a fixed width, labyrinth weirs have a longer crest distance when compared to linear one. Most weirs create a relatively static water zone in their upstream, which can be the site for sedimentation and waste materials, which is a disadvantage of these structures. Because of the sediments deposition in upstream of the weirs the flow conditions change and the accuracy of the presented relationships is reduced. Although numerous methods of design have been published for labyrinth weirs, there is insufficient design information available about the combined models of Labyrinth weir-gate.

This study was conducted to improve labyrinth weir -gate design and analyses techniques using physical-model-based data sets. The experiments were conducted in a metal and glass flume with a rectangular cross-section. The flume was 0.25 m wide, 0.5 m deep, and 10 m long. In each test the upstream subcritical depth was measured using point gauges of 0.1 mm accuracy The location for measuring the total head of the water upstream of the weir is a horizontal distance of three to four times the maximum water head on the crest of the weir. The discharge was measured with a triangle sharp weir placed at the end of the flume. The discharge-head relationship (Q-h) for triangular weir in experiments is as Q=0.6918 h2.5. The trapezoidal labyrinth weir-gate models was installed at the distance of 3 m of the beginning of flume. The base material roughness was made of natural sand with a mean diameter of 3 mm. In this research, experimental study of combined flow trapezoidal labyrinth weir-gate with one cycle has done for three sidewall angles of 15, 20 and 25 degrees, three gate openings 2, 4 and 6 cm and the weir height of 14 cm in a rectangular channel. According to the effective parameters of the combined models including sidewall angel (), gate opening (a) and the hydraulic head (Ht), the discharge coefficient has evaluated. By applying the Buckingham π theorem an equation was obtained. The discharge coefficient of trapezoidal labyrinth weir-gate can be expressed as a function of the variables of Fr,Re,We,H_t/P,L/H_t ,H_t/a,ϕ,α. In this study, the depth of water measured on the weir crest is at least 3 cm, so the effect of surface tension on the weir (We) is negligible. The effect of dynamic viscosity on the hydraulic behavior of the flow can be ignored. Therefore, the Reynolds number (Re) can be removed.

The results show that the discharge coefficient decreases with increasing the ratio of Ht/P for both smooth and rough beds and it reaches a constant discharge coefficient for Ht/P >0.6. According to the effective parameters of the combined models, the discharge coefficient has obtained averagely in the range of 0.61-0.75. The discharge coefficient of the combined flow increases with increasing angle of the weir. The increase in discharge coefficient is due to the decrease in the length of weir which decreases the flow mixing. Also for a specified angle, the discharge coefficient increases with increasing of L/ Ht then gets a constant value. The effects of artificial roughness on discharge capacity are also presented. It can be shown that the discharge coefficient increases in rough bed condition compared to the smooth bed condition. The present test data and those of Crookston (2010) were compared and it can be seen that the discharge coefficient in combined flow trapezoidal labyrinth weir-gate is more than the discharge coefficient of the trapezoidal labyrinth weir (without gate) in Crookston (2010) investigation.

The discharge coefficient of trapezoidal labyrinth weir-gate has the highest value for weirs with a sidewall angle of 25° and gate opening of 6 cm in rough bed condition about 17% more than the smooth bed. Among the different experimental models with a sidewall angle of 25, the labyrinth weir-gate in the rough bed condition has the highest discharge coefficient (approximately 0.93) compared to the smooth bed (approximately 0.61).

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.

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.

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.

The hydraulic jump is often applied as an energy dissipator below weirs or spillways of dams, chutes, gates, drops and other structures might be utilized in this regard. In the hydraulic jump, the water depth increases abruptly and some of the kinetic energy is transformed into potential energy, with some energy irreversibly losses through the turbulence. Determining the dimensions of the stilling basin is an important task for the hydraulic engineers to design a safe and economical energy dissipator and to reduce the construction costs of stilling basin, a change in the plan and profile sections of the basins can be useful. Arbhabhirama and Abella (1971) studied radial hydraulic jumps in a gradually expanding channel of rectangular cross section with divergence angles from 0 to 13°. The results showed that the divergence of the walls causes reductions in the sequent depth and the length of jump and an increase in the energy loss as compared to the hydraulic jump in a straight rectangular channel. Ead and Rajaratnam (2002) conducted an experimental study of the hydraulic jump on corrugated beds and specified that the reduction of the tailwater depth depends on increasing of bed shear stresses, which in turn are generated by interaction of the supercritical flow with the bed corrugations. Channels with trapezoidal cross-sections was carried out by Omid et al (2007). They found that the sequent depth and the length of the hydraulic jump decreased, whereas the energy loss increased with the increasing bottom width. Abbaspour et al. (2009) investigated the effect of sinusoidal corrugated bed with different wave steepness on the basic features of the hydraulic jump. They showed that the length ratio and the tailwater depth ratio of the jump on corrugated beds are smaller than that of the corresponding jump on a smooth bed. Chanson and Carvalho (2015) using an integral form of the continuity and the momentum principles, proposed an equation for calculating the sequent depth ratio of the hydraulic jump in an irregular channel. Daneshfaraz et al. (2018) studied the effect of sand bed with median size 1.9 cm on S-jump characteristics. The results showed that the abruptly expansion stilling basins with a rough bed in all the expansion ratios reduced the depth ratio and average jump length compared to an abruptly expansion stilling basins with smooth bed. The main purpose of this research is to study the effects of expansion ratio of the side walls channel and the discrete roughness elements height on the characteristics of the hydraulic jump such as the sequent depth, the jump length, the energy dissipation and the bed shear stress.

The experiments were conducted in a hydraulic laboratory of the University of Tabriz in a metal-glass horizontal rectangular flume. The facility had been relatively large-size channel 0.5 m wide, 0.5 m high and 10 m long. The sidewalls had been made of glass for observational purpose with 0.5 m high and 2.1 m long. The inflow conditions were controlled by a vertical sluice gate with a semi-circular rounded shape (Ø = 0.2 m) and the downstream coefficient of contraction was about unity. Also, the downstream flow conditions were controlled by a vertical gate. The upstream gate opening was fixed (2.1 cm) in all of the conducted experiments. To investigate the effect of roughness, discontinuous dissipative elements of lozenge shape with two heights (1.4 and 2.8 cm) were installed on the horizontal bed. Three glass physical models were built with divergence ratio (B = b1/b2) of 0.4, 0.6 and 1 (where b1 and b2 are the widths of the stilling basin in upstream and downstream of the hydraulic jump, respectively). During the jump, flow depths were measured using ultrasonic sensors Data Logic US30 with operation range of 10–100 cm and accuracy of ±0.1 mm that were mounted above the channel. The length of the hydraulic jump was measured by a fabric ruler with a reading accuracy of ±1 mm installed along the channel.

In this paper, the main features of a hydraulic jump under both the effect of the height of bed roughness and expansion of basin walls condition were investigated. Experimental observations showed that installing roughness elements stabilized the hydraulic jump on the channel. Equations (8), (9) and (10) were proposed for estimating the sequent depth ratio (y2/y1), the relative length of the hydraulic jump (Lj/y1) and the relative loss of energy (EL/E1), respectively. The Equation (8) shows that the sequent depth ratio increased with the increasing inflow Froude number and the divergence ratio. Also, the sequent depth ratio decreased as the roughness elements ratio increased. The relative length of the hydraulic jump for a given inflow Froude number, decreased as the roughness elements ratio increased. A comparing between the measured values of EL/E1 and those calculated by Equation (10) showed that, Equation (10) allows an estimation for calculating the relative energy loss in expanding basin with roughened bed. Also, the results indicated that the value of ε in the hydraulic jump on rough beds is increased compared with the smooth bed in all expansion ratios. Furthermore, the roughness height of 2.8 cm is more effective in creating high turbulence, force and increasing the coefficient of bed shear force.

Knowledge of the turbulence characteristics in open-channel flow is of importance in hydraulic engineering. Phenomena such as the flow resistance are linked to the velocity distribution and the characteristics of the turbulence structure. Kironoto and Graf (1995) studied turbulence structure of rough, non-uniform open channel flow and measured velocity, turbulence intensity and Reynolds stress profiles. They reported that the turbulence intensities and Reynolds stress decrease in accelerating and increase in decelerating flows (compared with the ones in uniform flow). Liu et al. (2004) presented a detailed study of the turbulence characteristics of hydraulic jumps at low Froude numbers (<3.3) using ADV. They noted that the ADV underestimates the mean velocity in bubbly two-phase flows. Yang et al. (2006) investigated the interaction of the vertical velocity v and the streamwise velocity u in a gradually accelerating flow. The analytical result shows that the non-zero vertical velocity causes the Reynolds shear stress profile to deviate from the conventional linear distribution in a 2-D flow. Islam et al. (2007) studied Turbulence characteristics downstream of a forced hydraulic jump using ADV. They founded that with the longitudinal distance Reynolds’ stresses decrease linearly and turbulence kinetic energy at each section decreases gradually. the results of Dey and Sarkar (2008) study showed that the rate of decay of jet velocity in a submerged jump increases with increase in bed roughness. Jesudhas et al. (2018) revealed that the expanding shear layer interacts with the free surface resulting in intense undulations and breaking up of the free surface. Most of the aforementioned investigations focused on the turbulent structures of the free or submerged jumps on smooth or rough bed in a rectangular channel. There is a considerable dearth of understanding of the effect of bed roughness and side walls divergence on the turbulent structures in submerged jumps. The present study aims to investigate turbulent characteristics of flow in submerged hydraulic jump over rough bed of stilling basin with divergent side walls.

The experiments were conducted in a hydraulic laboratory of the University of Tabriz in a metal-glass horizontal rectangular flume. The facility had been relatively large-size channel 0.5 m wide, 0.5 m high and 10 m long. The sidewalls had been made of glass for observational purpose with 0.5 m high and 2.1 m long. The inlet flow conditions were controlled by a vertical sluice gate. In order to create a desirable submergence factor in the flume, the tailwater depth was controlled by an adjustable tailgate located at the downstream end of the flume. The upstream gate opening was fixed (2.1 cm) in all of the conducted experiments. To investigate the effect of roughness, discontinuous dissipative elements of lozenge shape with two heights (1.4 and 2.8 cm) were installed on the horizontal bed. Three glass physical models were built with divergence ratio (B = b1/b2) of 0.4, 0.6 and 1 (where b1 and b2 are the widths of the stilling basin in upstream and downstream of the hydraulic jump, respectively). During the jump, flow depths were measured using ultrasonic sensors Data Logic US30 with operation range of 10–100 cm and accuracy of ±0.1 mm that were mounted above the channel. Submergence ratio (S) which is defined as (〖(h〗_t-h_j)⁄(h_j)), whereas h_t= tailwater depth and h_j= conjugate depth of free jump. It was important that h_t was measured at the location where the free surface profile became parallel to the bed, and h_j was estimated from the well-known formula of the conjugate depth of free jump which is 0.5b(√(1+8〖Fr〗^2 )-1). The instantaneous velocity components were extracted by a SonTek acoustic Doppler velocimeter (ADV). The ADV measurements were taken in the central vertical axis, which is along the centerline of the flume in vertical lines at different streamwise distances from the sluice gate. By computing the values of signal correlation coefficient (COR) and signal-to-noise ratio (SNR) for each of the three ADV receivers, the accuracy and the quality of the collected data were controlled.

The flow field in submerged jump on horizontal channel with gradually divergent side walls and rough bed was measured by an acoustic Doppler velocimeter. The vertical distributions of time-averaged velocity components, turbulence intensity components, and Reynolds stresses at different streamwise distances from the sluice opening and the horizontal distribution of bed-shear stress have been presented. Presented charts provide a good understanding of the process of decay of jet velocity in submerged jumps on rough beds. The bed-shear stress decreases with increase in streamwise distance and increases with increase in bed roughness. The important observations of the turbulent structures of submerged jumps on channel with gradually divergent side walls and rough bed are summarized below:With increase in bed roughness and decrease in side walls divergence, maximum values of u ̂ occurrence depth (compared to channel bed) would be increased.Increasing bed roughness would results increase in the growth rate of boundary layer which produces more shear stress and more energy dissipation.Variations of u^+ is more than v^+ which is causing more jet distribution ratio in horizontal axes vs vertical axes.Increasing bed roughness and decreasing side walls divergence would increase 〖uv〗^+Reynolds’ stress and turbulence.The length of fully developed zone reduces with increase in bed roughness and reduce in divergence ratio.The bed-shear stress decreases with increase in streamwise distance and increases with increase in bed roughness and decrease in side walls divergence.

This study investigated the performance of a labyrinth weir with a trapezoidal cross-section at different heights. For this purpose, the geometry of the weirs was designed in Inventor software, and simulation was performed in Flow3D software. Validated the model with laboratory data, and the results of the model were in good agreement with the results of laboratory data. Examined the numerical model at three heights of 10, 14 and 18 cm and three different angles and two apex widths; Analysis of the results showed that with decreasing the weir height (P), the discharge coefficient (Cd) increases. Reducing the weir height by 44% increased the average discharge coefficient by 2 to 3%. In all simulated models, with decreasing relative water head, the decreasing trend of discharge coefficient was also reduced. During the constant crest length, with a 100% increase in the weir angle, the discharge coefficient of all three weir heights increased by 20 to 25%. A 40% increase in crest length at a fixed angle increased the average discharge coefficients of all three heights by 12 to 15%. As a result, at a constant angle, the increase in crest length is greater than the second case (constant crest length and increase in weir angle) on the flow rate; This is important in designing labyrinth weirs to have a maximum discharge coefficient and should be considered.

Labyrinth weirs are considered as an appropriate choice to correct the weirs that are having difficulty in passing the maximum possible flow. For this purpose, in the present study, a new weir was introduced called the of pseudo-Cosine labyrinth weir. First, models with different widths and heights were built in FLUENT software as a virtual laboratory. The anti-corona algorithm and adaptive neuro-fuzzy inference system (ACVO-ANFIS) were used for predicting discharge coefficient. of pseudo-Cosine labyrinth weir. Validation of the proposed method was performed using Experimental data. Then, to identify the superior model and determine the parameters affecting the discharge coefficient of pseudo-cosine labyrinth weir, the combination of different dimensionless parameters was evaluated. The performance of the proposed method was evaluated with five statistics, including determination coefficient (R2), root means squared error (RMSE), mean absolute percentage error (MAPE), nash-sutcliffe (NSE), and relative root mean square error (RRMSE). The results showed that in low hydraulic heads, the discharge coefficient has its highest value. As the radius increases, the discharge coefficient increases due to the increase in the effective length of the labyrinths. At a constant H/W, with increasing weir height, the discharge coefficient increased. The results of the ACVO-ANFIS model showed that the input variables are the ratio of the radius to the weir height (R/W), the ratio of the length of the weir to weir height (L/W), and the ratio of the hydraulic head to the weir height (H/W), with error values R2=0.971, RMSE=00.9, MAPE=0.006, RRMSE=0.010, and NSE=0.977, the most effective parameters in determining the discharge coefficient of pseudo-cosine labyrinth weirs.

Among the regulator structures used in water projects, weirs have remarkable applications like measuring flow, maintaining water level, controlling sediment transport, and managing variable water inflows. Weirs can be classified on the weir axis direction as a normal, side, or a labyrinth weir. labyrinth weirs are hydraulic structures used to regulate water levels and control flow in reservoirs of dams, canals and rivers.The discharge coefficient in the weirs is directly proportional to the crest length of weir. If the width of the channel or reservoir where the weir made is limited, one of the ways to increase the capacity is to increase the crest length of weir by zigzagging the weir in the plan. Due to their complex geometry labyrinth weirs are expensive to build. Therefore, in laboratory studies, high cost is one of the reasons that has made it difficult to investigate this type of weir comprehensively. Numerical methods are a very good option for hydraulic analysis of labyrinth weirs hydraulic. The history of the construction of labyrinth weirs goes back to before the year 1920 (Darvas, 1971). labyrinth weirs were first investigated by Gentellini )1940(. Vahab nezhad (2017) studied the changes in discharge coefficient for the three angles of 15, 18 and 23 degrees. Zamiri, et al. (2016) showed that increasing the thickness of the labyrinth weir wall increases the depth and velocity of the flow and ultimately reduces the discharge coefficient. The results showed that the discharge coefficient increases with increasing the weir angle, because as the weir angle increases, the weir length decreases and the discharge coefficient increase.In this study, the weir performance of a trapezoidal labyrinth with different angles (α) was investigated. For this purpose, labyrinth weir modeling was performed with three angles of 15, 23 and 30 degrees for two crest length of 5 and 7 cm and three heights of 10, 14 and 18 cm. The geometry of the weirs was created in the Inventor software and simulation was performed in Flow3D software. In order to validate the simulation and adjust the software parameters, valid laboratory data were used and the results of the model were in good agreement with the results of the laboratory data. For this purpose, the discharge coefficient of numerical models (Cd (CFD)) and laboratory (Cd (EXP)) for different values of water to overflow ratio (h / p) were compared and the error value was calculated. The highest error rate is 5.88 and the lowest is zero. In fact, with increasing the ratio (h/p) the error rate has increased, but this increase is also acceptable and the results show that Flow3D software has a very good ability to simulate labyrinth weir. Flow field study was performed with different turbulence models in Flow3D software using laboratory data. The RNG model was used in all simulations. To mesh the model, the channel was divided into three parts: initial, middle and end. The dimensions of the cube of the initial and final parts are 1 cm and the middle part is 5 mm.Analysis of the results showed that increasing the weir angle in a fixed crest length, increases the discharge coefficient (cd). The inverse relationship between the relative hydraulic load (h/p) and the discharge coefficient was also determined. Increasing the crest length of the weir by 2 cm, the trend of increasing the discharge coefficient due to increasing the weir angle, decreased by 9%. Also, increasing the angle 15 degrees, the trend of increasing the discharge coefficient due to increasing the crest length, decreased by 5%. This means that at higher angles, the effect of increasing the crest length on the discharge coefficient decreased and during shorter crest length, the effect of increasing the angle on discharge coefficient increased. Due to the direct relationship between the discharge coefficient and the average flow velocity, simultaneous increase crest length and weir angle increased the average flow velocity by 4 times at the beginning of the channel floor impact. In cases where the purpose of the study is to increase the discharge coefficient by increasing the angle and length of the weir crest, it should be noted that the effect of increasing the angle and length of the weir crest is more noticeable at low altitudes, So that with increasing the height of the weir this amount decreases.

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%.

Labyrinth weirs are important hydraulic structures for water level regulation and flow control in canals, rivers, and reservoirs. Due to the uneven distribution of hydraulic head on the weir crest, the discharge coefficient changes along the labyrinth weirs are noticeable. For optimal use of this type of weir, it is necessary to estimate the discharge coefficient. In this regard, in this study, using a data set including 120 experimental data collected by Kumar et al. (2011) and numerical (simulated by FLUENT software using k-ε RNG turbulence model) to optimally estimate the discharge coefficient of triangular-duckbill labyrinth weir embedded in a rectangular channel 0.28 m wide, 12 m long and 0.41 m high was addressed using modern gray wolf meta-heuristic (GWO) and election (EA) algorithms. To investigate the effect of discharge coefficient, angles of 30, 60, 90, 120, 150 and 180 degrees with weir height of 10 cm were selected and the flow conditions in all cases were considered as subcritical, turbulent and falling flow. The objective function is the sum of the squares of the difference between the computational flow and the observations defined as the minimum. Comparison of the results of GWO and EA algorithms and FLUENT software with values of R2=0.96 and NRMSE=0.052 in comparison with the observed values, shows a good agreement between the observed and computational values.

The combined weir- gate is important hydraulic structure in management of irrigation canals. On the other hand, the use of labyrinth weirs can reduce water level fluctuations due to longer crest lengths than linear weirs for a specific discharge. Because of the sediments deposition in upstream of the weirs the flow conditions change and the accuracy of the presented relationship is reduced. Therefore, the use of combined flow trapezoidal labyrinth weir-gate can be a useful solution for passage of floating substances over the weir and sediment transport under the gate. In this research, experimental study of combined flow trapezoidal labyrinth weir-gate with one cycle has done for three sidewall angles of 15, 20 and 25 degrees, three gate openings 2, 4 and 6 cm and three weir heights of 14 , 17 and 20 cm in a rectangular channel. Based on the effective parameters of the combined models, the mean discharge coefficient has obtained in the range of 0.61-0.75. The results show that the discharge coefficient decreases with increasing the ratio of Ht/P, and it reaches a constant discharge coefficient of 0.61 for Ht/P >0.6. The discharge coefficient of the combined model increases by increasing the angle of the weir. Also the results show that the discharge coefficient of trapezoidal labyrinth weir-gate has the highest value for weirs with a sidewall angle of 25 ° and gate opening of 2 cm.

Detention ponds are best management practices designed for the control of urban stormwater and their design objectives are mainly controlling the quantity and quality of urban stormwater at the minimum cost. In this research, long term hourly rainfall data of Kerman and Mehrabad synoptic stations were analyzed and the three rainfall characteristics (rainfall duration, rainfall volume and inter event time duration) were obtained. Analytical probabilistic models (APM) were employed and the model parameters were derived from the closest stations to the study areas. The APM parameters, along with the catchment parameters, were used to develop the optimal combination of the pond volume and outlet capacity. Also, the PSO model led to lower computational   costs in comparison with the APM model. Comparison of the PSO with APM showed that the PSO results were more accurate than the results of APM and there was no need for determination capacity in the forementional model as it did not need outlet size. The PSO model was also found to be more computationally implemented more cheaper and faster.

Investigation of the shear stress to estimate the scour hole around bridge piers is of utmost importance, but a review of the literature shows that the study of this factor, around protected piers by various methods of scour control has not been studied by the researchers. In this research, a three dimensional numerical model has been used to study the variation shear stress on the bridge pier with submerged vanes. However, due to difficulty of calculating the amount of shear stress in the wild, researchers provided indirect ways to calculate these parameters that one of these methods, is the use of quasi-two-dimensional model Shino and Knight (SKM In this study, the pattern of shear stress distribution around the base with a different number of vanes (2, 4 & 6), with the two angle of the flow (20 and 30 degree) and in flow intensity 0.95 (critical flow intensity), with both methods were studied and compared. Both model results show that vanes placement has a great effect on reducing velocity of the passing flow and thus decreasing the bed shear stress around the pier. Also analysis of the counts and placement angles showed that 6 vanes rather to 2 and 4 vanes and also angle of 30 degree rather to angle of 20 degree performs better in action, so that the shear stress reduces the amount of 12-15 percent.

Seepage from the earth canals is considered as the main portion of water losses in the irrigation projects. Several empirical equations have been proposed by researchers to estimate the seepage losses in canals. Some of these equations estimate accurately but the others should be used with more cautious. Unfortunately, few previous practical formulas for estimating the seepage losses along the earthen canals are applicable and new design equations are needed. Because of complexity, more practical tools are required to model seepage processes. The geometric factors involved in the estimation of seepage are the shape and dimensions of the canal. Regression relations are most commonly used to predict the seepage rate from the earth canals; however the regression analysis can have large uncertainties. Thus, the computed seepage values can be far from the actual ones. Also, the regression analysis has some limitations by predefined equations for modeling. So, gene expression programming (GEP) has been used to model these processes, recently. Through the present paper, some experimental data measurements have been carried out, on trapezoidal earthen canals with different geometry for seepage analysis, and the equations were developed for relating the seepage losses, qs, to the flow and geometry canal parameters. The dimensional analysis of the seepage rate in the canals has shown that the parameters z, k and y are effective in the seepage discharge, qs. As is evident, the dimensionless parameter q/ kh, is a function of the channel side slope, (z), the water depth (y) and the hydraulic conductivity of soil (k) considered as variable parameters. For each of the three samples the hydraulic conductivity of soil was calculated from Darcy relationship, So that in each instance the measurement and estimation of seepage (by the volume method) and the water level measurement in the parameters were done, then the average hydraulic conductivity of soil was calculated and the seepage line was defined for each soils. In artificial intelligence, gene expression programming (GEP) is an evolutionary algorithm-based methodology inspired by biological evolution to find computer programs that perform a user-defined task. The effect of the side slope, the water depth and the hydraulic conductivity on seepage rate, qs, in the trapezoidal earthen canals was studied. This study presents gene expression programming (GEP), as an alternative tool in the prediction of the seepage losses in the earth canals. In GEP model they were used arithmetic operations like (*+ , − ,/ ,) and functions such as ( sqrt and power). The performance of GEP in training and testing sets is validated in terms of the common statistical measures R, the correlation coefficient, the root-mean-square error (RMSE). The R shows the degree which two variables are linearly related to. The experimental results showed that the seepage rate increased by increasing of the water depth in canal and hydraulic conductivity of soil, but the seepage rate was not directly related to the canal side slope. In small and narrow earthen canals, the seepage rate initially decreases and then increases with increasing the side slope, z. Considering that, the local features of seepage is a unique, the trapezoidal section with slope Z = 2 in the range of 1.5< Z< 2.5 had the minimum seepage rate. Also, the results of the sensitivity analysis indicated that the parameter k had the greatest impact on the rate of seepage. In general, the performance of GEP models was superior to the statistical regression schemes. These models could be successfully used in computation of the seepage in the canals. Based on the results, model performance can be evaluated as satisfactory, if R> 0.9 and less values of RMSE. The results of GEP were compared with measured values of experimental model. The comparison showed that this software had a good performance in modeling the seepage of earthen canals. The seepage rate calculated by GEP had little difference with the measured seepage. The GEP model performed well in simulating the seepage rate based on all parameters and for each of canal side slopes. The simplified analytic form of the proposed GEP model for qs can be expressed as a function of y, z and k parameters. The equation obtained by GEP is clear and precise function that can be used to calculate the seepage losses from earthen canals in similar situations.

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.

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.

In this study, the characteristics of the hydraulic jump on semi cylindrical rough bed a diverging stilling basin has investigated experimentally. The experiments have done with the walls diverging angles of 0, 2, 4, 6 and 8 degree for six different Froude numbers. Total of 200 tests were performed within the range of 5 to 8 Froude numbers. The relative depth reduction of jump for the angles of 0, 2, 4, 6 and 8 degrees have obtained 10.5, 17.7, 22, 26 and 26.2 percent respectively. The average reduction of length jump for the angles of 0, 2, 4, 6 and 8 degrees with the rough bed have obtained 47.9, 57.4, 59.9 ,65.9, and 68.2 percent respectively and in the optimal case (C2.2D) the reduction of length jump is 75 percent. The divergence of a basin without roughness effect also has influenced on reducing the relative length of jump about 37 to 47 percent and the relative length of jump are directly related to the angle of a divergence basin.

The compound arched circular-trapezoidal sharp-crested weirs are combinations of a circular arch notch at the bottom part and a trapezoidal notch at the top of the cross section. In this research, the discharge coefficient (Cd) of compound arched circular-trapezoidal sharp-crested was investigated. The experiments were conducted on weirs having the crest width of 15 cm, crest height of 15, 20, 25 cm and circular arch notch height of 5, 7.5 cm with different curve radii and the side walls slope of 0.5 (0.5H:1V) in a laboratory flume. The results indicated that the amount of discharge coefficient was in the range of 0.56 to 0.81. For a given hydraulic head, the amount of Cd is reduced approximately up to 5% by increasing the height of weir crest. In addition, for a given hydraulic head, by changing the height of circular arch notch, the amount of Cd for the compound arched circular-trapezoidal sharp-crested weirs increased about 25 to 30 percent with respect to the trapezoidal weirs. According to the root mean square error (RMSE) with value of 0.0563, the amount of Cd for the compound arched circular-trapezoidal weirs was estimated with acceptable accuracy, using a linear combination of the discharge relationships of circular and trapezoidal weirs. In this research, the discharge continuity over the compound weir for the various hydraulic heads was examined using the experimental data. The results showed that the least amount of discontinuity could be seen in the wide range of discharges.

Hydraulic jump is a rapidly varied flow in open channels which performs an effective role in dissipation of the kinetic energy of flow at downstream of water structures. In the present study the characteristics of hydraulic jump, including sequent depth, energy dissipation, bed shear stress and velocity profiles at different sections, on rough bed with discontinuous roughness elements of lozenge shape have been investigated. The experiments were carried out for a range of Froude number values from 4.3 to 12.4 in three roughness densities and four combined arrangements of roughness elements. The results of this study showed that the velocity profiles on rough beds were similar but somehow different from those of wall jet on smooth bed. The dimensionless boundary layer thickness was 0.53 on rough bed that was more than corresponding value on smooth bed with the amount of 0.16. As the roughness density increased the bed shear stress produced by the interaction of upstream supercritical flow with the roughness elements enhanced so the energy loss increased and as a result the sequent depth decreased. In the arrangement of ternary combination of roughness elements with density of 10.67 % the maximum reduction value of the sequent depth was about 29.39%, the increase of the energy dissipation relative to hydraulic jump on smooth bed was10.94% and the bed shear stress coefficient on rough bed was about 13.54 times as much as its corresponding value on smooth bed.

Hydraulic jump is the most important phenomenon in the rapid variable flow is of interest to hydraulic engineers. It has been used for dissipation of kinetic energy downstream of hydraulic structures such as spillways¡ chutes and gates to protect stilling basin. This study the roughness of the bed and the divergence of basin have studied simultaneously. The experiments have done with the walls diverging angles of 0¡ 2¡ 4¡ 6 and 8 degrees for six different Froude numbers. In total¡ 190 tests were performed in the range of 5 to 8 Froude numbers. The relative depth reduction of jump in the angles of 0¡ 2¡ 4¡ 6 and 8 degrees have obtained 10¡ 17.2¡ 22¡ 25 and 25.5% respectively. The average reduction of length jump¡ T¡ for the angles of 0¡ 2¡ 4¡ 6 and 8 degrees with the rough bed have obtained 45.5¡ 55¡ 56.1¡ 64 and 66.2% respectively. The man reduction of length jump for the cube bars is 60.3%. The loss of energy in the jump EL is equal to the difference between the specific energy before and after the jump¡ E2 - E1. The relative energy loss¡ EL/E1¡ for the angles of 0¡ 2¡ 4¡ 6 and 8 degrees have obtained 58.5¡ 62.4¡ 64.1¡ 65.9 and 67% respectively. In this study¡ the effect of the square ribs bed on hydraulic jumps was investigated. The divergence of basin without roughness effect also has influenced on reducing the relative length of jump about 37 to 47% and the relative length of jump is proportional to the angle of divergence basin. The results show that both the divergence angle of stilling basin wall and bed roughness of bed have reduced the length and depth of hydraulic jump. This makes it more economical to build a basin and control of jump is better.

The velocity distribution is almost the most important argumentation in all of the open channel flows studies, since it is necessary for study of the mean and maximum velocities, estimation of discharge as well as for evaluation of shear stress on channel sides. The flow velocity distribution in a channel cross section depends on the shape of the section, the roughness of the channel, and the presence of the bends. So, it should be investigated before solving many of hydraulic problems in open channels. Characteristics of the roughness which mostly affect the flow are the size and shape of the roughness elements and spacing between them and also, the roughness concentration. In this study, velocity profiles in open channels with rough bed were investigated. FLUENT CFD package was used to implement the numerical method on the basis of the finite volume method. Results showed that the flow velocity along the canal increased over the rough bed. So, the shear stress, slope of the water surface and energy lose were increased in the flow direction. The skin friction coefficients were determined for different rough beds which were in good agreement with the numerical model values. As the number of roughness elements became more, their effects on velocity profiles were increased.

General assumption in designing cut off walls is that the seepage be held in a limited amount. In order to control the seepage, the foundation drains are located in parallel to cut off wall at downstream. The main aim of foundation drains construction is to collect seepage water and decrease uplift force. Numbers, distance, and diameters of these drains need technical judgment about characteristics of foundation stones. The depth of drains depends on cut off wall characteristics. In this study, the performance of drains in foundation of concrete gravity dam was investigated using finite element method (FEM) via Seep/w software. Among influential parameters in studying the drain effects, one might consider diameters, center to center distance, and distance of the drains from upstream of dam. In this paper effective parameters on uplift force were analyzed and it was found that increasing the drain diameter had lesser effect on decrease of the uplift force slightly compared to the other parameters. In the other words, selecting the best diameters depends on executive consideration. But decreasing the distance of drains and also their distance from upstream of dam would play an important role in decreasing the uplift force. Focusing to the simulated range of parameters, the drains with 15 centimeter diameter and distance of 3 meters had the optimum performance and the best operation in decreasing uplift force. For validation, the numerical method used in this research was compared with the other analytical methods and the proper agreement with them was observed.

One of the non-linear weirs is horseshoe-shaped weir that determination of its hydraulic parameters for designing of that is necessary. Sometime due to limitation in dam site and also reduction in soil excavation volume, tunnel and intake location of hydro-electric power this structure is needed to be constructed near the dam and its intake. In these cases, a combined structure of both the intake and spillway can be constructed by using horseshoe-shaped weir to achieve a proper economic condition in dam construction. In this study, by making physical models of the horseshoeshaped spillway in laboratory dimension, some hydraulic parameters like discharge coefficient, velocity and water surface profiles in different parts of the horseshoe-shaped spillway were investigated. Results showed that in horseshoe-shaped spillways, with increasing the ratio of head to spillway length, discharge coefficient was decreased about 0.6 to 0.7. This reduction in discharge coefficient had different trends for spillways with length of greater or less than 112cm. Comparison of the results between the rectangular weir and the horseshoe-shaped spillway by consideration an equal width for them showed that horseshoe-shaped spillway could reduce head above the weir about 54%. Investigation of the water surface profiles showed that overflowing of waters into the horseshoe spillway, created the rooster tail type hydraulic jump.