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Today, the use of intelligent models in simulating runoff has been widely used in water resources management. In this study, in order to predict the daily flow time series of the Morghak hydrometric station in Karun basin, an intelligent model of artificial neural network combined with wavelet analysis has been used. For this purpose, the ERA-INTRIM observational and analytical precipitation time series for 16 years (1378-1382) was decomposed by wavelet transform into frequency subsets, then each subset separately as input data to the artificial neural network model was introduced. The results showed that the analytical data have a high ability to simulate runoff precipitation models and can be a good alternative to observation data of rainfall stations. Also, according to the results of the wavelet transform technique, it can be effective in improving the performance of the simple ANN model for the Bazoft basin by 38% on a daily scale and 72% on a monthly scale.

Rivers are known as the main sources of surface water in the world, which experience seasonal fluctuations in water level. These resources have severe damage to human societies and nature in flood conditions and have irreparable consequences in the drought seasons. Optimal utilization of these resources with maintaining the environmental conditions of the waterway and minimizing flood damage is considered one of the river engineering goals. Since the conventional methods of river management are imposed serious environmental threats on waterways and wetlands, consideration to these water resources requires attention to issues related to plant ecosystems, solving challenges of coastal bed erosion and predict the condition and management of the river in the future (Callow, 2012; Dawson and Haslam, 1983; Fan et al., 2013; Rose et al., 2010; Rowinski et al., 2018). One of the strategies that cause loss of flow energy in the river improves the hydrological system and river ecosystem is the presence of vegetation in the river banks and floodplains. Native vegetation in floodplains and coastal forests plays an important role in conserving waterway ecosystems, flood management, coastal protection in urban lands and agriculture adjacent to the river (Fathi-Moghadam, 1996). Vegetation will also control the width of the river and increase the stability of the shores by absorbing and settling suspended sediments in river banks. The plant species along rivers and waterways are composed of various vegetative components, mainly affected by the environmental conditions of their habitat, including the distance from the waterway bed, hydrological characteristics of the river, climatic and soil conditions. Obviously, the effect of each plant species in the ecosystem cycle varies and for each section of the river, a specific combination of plants will create optimal conditions.

The analysis of transient flows in closed ducts has always been one of the most important and favorite topics of hydraulic engineers. On the other hand, with operation of water supply facilities during the time, water leakage may occur anywhere in the transmission pipeline system. Haghighi and Ramos (2012) performed leak detection in pipelines using inverse transient analysis and CFO optimization method. Mohammadi and Fathi-moghadam (2013) analyzed the fast transient flow in pipelines by the unsteady friction model. Akbari et al. (2021) investigated the detection of leaks in polyethylene transmission pipelines using pressure wave reflection of transient flow. Therefore, using laboratory modeling, fast unsteady flow in leaking pipelines was investigated, and then, a computer model was coded by Visual Basic programming language, with the ability to simulate transient flow in pipelines in presence of leakage. Then the parameters of temporal and spatial acceleration coefficients kut and kux and discharge coefficient of leak orifice cd were calculated.

In this research, a 47m long pipe that made of polyethylene with 10bar nominal pressure and diameter of 63mm was used in experiments. The transient flow was generated in it by very fast closure of the end valve. A computer numerical program was developed to simulate the hydraulic conditions in pipeline. The coded model analyzer motor analyzes the basic unsteady flow equations in pressurized ducts, and the inverse analyzer is an optimization algorithm using a defined goal function to find the best fit of the recorded pressure waves and those simulated with the least error. Also, the boundary conditions for simulating the leak in the pipeline were included in the numerical model.

The values of kut and kux coefficients related to the wave simulations was calculated. The values of kut for leakage and non-leakage state were approximately the same, and the coefficient of kux for leak state would be less than non-leakge state. In the case of leaks with different diameters, the coefficient of kut were generally the same as in the case of non-leakage. However, the values of kux coefficients for leakage with a diameter of 4 mm were greater than those for leakage with a diameter of 10 mm, and both of these values were less than non-leaking. The reason is that as the diameter of the leak increases, the damping rate of the pressure waves increases, therefore the value of the kux coefficient decreases.The change in the leak location had almost no effect on the values of kut and kux. The coefficient of kux in the presence of leak, either at a distance of 27 m or 39 m, were less than its values in non-leak state, and both values were also approximately equal to each other. Leak orifice with a larger diameter (10 mm) had a higher discharge coefficient than leak with a smaller diameter (4 mm), due to their lower resistance and lower energy dissipation against the increase in pressure produce in the system by the transient pressure wave. The performance of the two-coefficient unsteady friction model was evaluated by statistical indexes. Also, the numerically simulated waves and the laboratory samples was compared to each other. The two-coefficient unsteady friction model had a good ability to simulate a transient pressure wave in presence of a leak.

The values of kut for leak and no-leak state were almost constant and the values of kux for leak state was less than the kux for the no-leak state. Changes in leak location had almost no effect on the values of kut and kux. Selecting a steady or unsteady type of friction model to simulate the transient flow in the presence of leakage had almost no effect on the orifice discharge coefficient. Two coefficient unsteady friction model had a good ability to simulate the pressure wave of transient flow in the presence of leakage.

The analysis of transient flow plays a critical role in designing pipe systems and pipe networks. Controlling and collecting the pressure wave signals at proper spots in the pipeline can provide much information about the system. Many researchers have studied transient flow and the loss caused by unsteady flow (Brunone et al, 1991; Pezzinga, 1999; Vitkovsky et al., 2000).
Compared with steel pipes, the use of polymer pipes such as polyethylene (PE) and PVC in pipelines and pipe networks has attracted much attention due to their superior properties. Researches have been conducted on the dynamic behaviour of these pipes on transient flow. Brunone et al. (1995) explained that pressure wave damping in a polyethylene pipeline is caused by unsteady friction loss; however, the research showed that there is a large difference between the numerical and the experimental results, and this is due to the viscoelastic effects of polymer pipe walls, which were neglected in this study. Soares et al. (2008) examined the viscoelastic behaviour of PVC pipes on transient flow. The creep function of these pipes was calculated by inverse solution of the transient flow. The results showed that the damping, scattering, and shape of the transient pressure waves are fully described by taking into account the viscoelastic behaviour in the developed numerical model. Carriço et al. (2016) studied the uncertainties of the transient flow numerical model in polyethylene pipes, indicating that unsteady friction loss and viscoelasticity of polyethylene pipe walls have parallel effects on transient signals and the effects cannot be simultaneously distinguished.
Most studies have been so far conducted on the transient flow in a simple pipeline made up of steel and concrete. Since few research has been done on transient flow in more complex systems and plastic pipes, the present paper investigates the numerical and experimental model of transient flow and its properties in polyethylene pipe networks in time domain. In this study, by collecting transient signals of the pipe network, unknown parameters are calibrated and extracted by inverse analysis of the transient flow for different discharges. The pressure signal properties in polymer pipes are also compared with discharge variations.

The complex interactions between streameise flow and curvature- induced secondary flow in bends, bed morphology cause erosion near the outer bank, and deposition near the inner bank, that it can endanger the outer bank’s stability and also reduce the navigable width of the rivers. There are several techniques to protect the outer bank, reduce adverse impacts and control bed erosion in bends. Methods used in most parts of the world include submerged groynes, spur dikes, and bandal-like structures. But, meny these Methods have the disadvantage of being fixed constructions on the bed river that caused a threat for navigation. This paper describes a new way that consists in changes the bed morphology with provoking changes in the flow pattern. Dugue, et al. (2011, 2012) studied morph dynamic bends rivers with the Air-bubble screen method. Their results reveal that the air bubble screen is able to modify the flow pattern by shifting the maximum scouring from the outer bank towards the center of the flume and does not endanger its stability anymore. Dugue et al, 2013 studied scour reduction at a 193° bend by an air-bubble screen method. Velocity pattern at 70° bend showed that the bubble-induced flow pattern overcame the secondary flow induced by the outer bank while decreasing the morphology slope. It also showed 50 percent reduction in the maximum scour depth. Shukry (1949) is one of the first researchers in the study of erosion of the outer bank of rivers in a canal with a 180- degree bend with various proportions of the rivers radius to its width. There have been very few investigations about air bubble screen in 90 bend, therefor  in this study the effect of the air bubble screen on flow pattern and Secondary flow strength  and bed shear stress in 90 degree bend under Froude numbers 0.45 is examine.

Measuring flow discharge in rivers and open channels has always been one of the most important concerns of water sciences experts. The most common flow measurement method in open channels is velocity- area approach. An approach recently considered as a non-contact option for measuring flow is the use of surface flow image velocimetry methods. Recently, the standard PIV method has been used to measure the velocity at larger scales and on the flow surface, which is referred to as the LSPIV (Bieri et al., 2009).The most common way of converting the surface velocity to the depth-averaged velocity is to use a coefficient called the Velocity Index (VI) which is in fact the ratio of the depth-averaged velocity to the surface velocity. In the literature, the value of the Velocity Index for river flows and laboratory flumes, which were mainly studied for subcritical conditions, is believed to be equal to 0.85, which seems to be an accepted value for this index among the hydraulics communities.In this research, an image velocimetry technique was used to study the flow characteristics, determine the Velocity Index and investigate the surface flow pattern. The instantaneous surface velocity field was measured using the LSPIV method and then a two-dimensional time-averaged velocity map was obtained for different experiments providing the possibility of comparing the flow pattern in different scenarios. Furthermore, by means of spatial averaging of the time-averaged velocity map, the double averaged surface velocity  was obtained using which and the cross-sectional mean velocity the Velocity Index was calculated. Therefore, the effect of channel slope and relative submergence on the Velocity Index was investigated and relationships were proposed to estimate the VI in steep slopes.

Hydraulic jumping is a complex three-dimensional phenomenon which is frequently observed in open channel flow such as rivers. The hydraulic resistance of vegetation plays a major role in the hydrodynamics of rivers with extensive natural floodplains. Vegetation penetrates the flow field and creates resistant force and, consequently, energy dissipation. In this study, the effect of vegetation density and height on flow in a hydraulic jump and parameters related to two phase Air-water flow are examined using cylindrical elements made of galvanized iron with a homogeneous diameter of 7 mm as vegetation. Thus, neither the effects of plant diversity nor flexibility have been considered. For this purpose, four forms of rough bed were used in two modes of staggered and collocated grid roughness with two heights of 1.5 and 3 cm, and the results were compared with data on smooth bed as a reference. Experiments were conducted in a horizontal rectangular flume with a width of 30 cm, in the range of upstream Froude numbers between 1.5 Fr1 5.5. Air-water flow measurements were conducted with a dual-tip conductivity probe, which was designed, developed and calibrated in this research. The results of this study showed that the presence of vegetation increases aeration by increasing the void fraction in a jump roller. And on the other hand, increasing the resistant force and shear stress in the bed reduces conjugate depths and roller length. This increase and decrease depends on the upstream Froude numbers, height and density of vegetation.

Introduction  When a sudden pressure surge is induced in a pipe system, discontinuities like leaks, changes of pipe diameter or material, tee-junctions, local head losses or air pockets, introduce changes in the hydraulic transient event propagation. A leak creates a pressure drop; friction increases pressure damping; a dead-end or a closed-valve reflects totally an incident wave; an air bubble creates a pressure drop followed by a pressure increase.     The detection of these signals allows their identification and location. The information carried in the transient pressure signal can be used to detect, locate and size leaks, and, eventually, to distinguish these from other features existing in the pipeline.   Methodology Physical model     The purpose of this study was to find the location and size of leakage in polyethylene transfer pipes using transient flow. Therefore, a laboratory model was developed for this purpose at the Hydraulic Lab of the Faculty of Engineering Sciences of Shahid Chamran University of Ahvaz.

Forests as Green Belt reduce the height and energy of waves passing through them, reducing their ability to erode sediments and to cause damage to structures such as dikes and sea walls, (Mclvor and et all.,2012). It is well-accepted that wave attenuation by emergent and submerged vegetation is a function of plant characteristics as well as hydrodynamic conditions, (Augustin et al., 2009). (Hirashi and Harada, 2003) showed that the pressure difference on the sides of the green belt is mainly due to drag resistance. this study a new and unique method based on the principle of momentum and direct force measurement has been used to measure wave energy decay simulated by the Green Belt.Most previous studies have been conducted to analyze the wave forces on emergent structures and obstacles. Relative submergence is considered to be the relative roughness of trees and is a factor influencing the resistance of the forest to the passage of waves, (Davoudi et al., 2016). So the resistance of the canopies in the submerged state is one of the important factors in wave damping. Also, in previous studies, variable still water depth has been considered to create different ratios of submergence, which will change the characteristics of the wave. Therefore, in the present study, decided that the resistance of the canopy against broken waves in the submerged state would be determined by changing the height of the obstacles, which will be examined in this study (Figure 1).Figure 1-- Schematic view of the Rigid vegetation with different relative depth of submergence

Experiments were conducted in the Hydraulic Modeling Laboratory of the Faculty of Water Engineering, Shahid Chamran University of Ahvaz, in a 8.3×0.8×0.55 rectangular flume called Knife Edge Flume. Flume has Plexiglas sidewalls and bed and designed to measure the force exerted by the wave force on the barriers at its shore by means of a dynamic load cell installed between the movable and fixed parts of the flume. At the beginning of the experiments, wooden circular cylinders with 1 cm in diameter, fixed parallel arrangement were placed in the moving part of the flume with constant slope of zero. By changing the height of obstacles and generating breaking waves with constant height the absorption force by the canopies was monitored via an electrical display connected to the dynamic load cell.

The submerged ratio of tree canopies is equal to height of inundation depth to height of trees. Therefore, in the submerged state, the ratio is greater than one, and in the emergent state it is less than one. What is important in this study is that different ratios of immersion with different heights of barriers have been created.

The term “Specific Surface Area” (SSA) refers to the area per unit weight of soil. SSA is a fundamental soil property that can be used as an indicator of soil behavior (Utkaeva, 2007) to explain many of the physical and chemical phenomena of the soil: including fertility-determining components (such as the water holding capacity, the adsorption of plant nutrients, and the amount of organic matter) (Voronin, 1975). Measurement of specific surface area is time-consuming and relatively expensive; therefore, its estimation by routinely measured soil variables is preferred. In the present paper two pedotransfer functions for estimating of total SSA (including external and internal specific surface area) was presented, one a multivariate pedotransfer function based on the standard deviation of the diameter of soil particles and clay percent and second an exponential pedotransfer function based on slope of linear regression equation of logarithmic PSD Curve.

Some events such as scour and deposition in rivers may endanger the stability of the outer bank’s bend and reduce the navigable width of them. So far, different techniques have been developed to control this phenomena such as bottom vanes, submerged groynes, bandal-like structures. In the present study, the influences of non-phase hydraulic jet usage on bed scouring and deposition in a 90 bend has been investigated experimentally. Experiments were conducted in a experimental channel to measure the variations of bed topography under a clear water condition. The90 bend is connected to an upstream straight reach 5 m long and a downstream straight reach 3 m long. The channel was rectangular having 70c m width and 280cm radius of bend to centerline. (R/B=4; where R=radius and B=flume width). Four Froude number values including 0.37, 0.41, 0.45 and 0.47 with a constant flow depth of 11cm under clear water condition were used for each test. Bed topography was measured with a laser meter and contour lines were plotted with the Tec plot360software. The scour geometry in a bend depends on channel geometry (channel width, channel , radius and bed slope), flow conditions (depth and discharge or velocity), non-phase hydraulic jet characteristics (length, angle with bank, location in bend), sediment properties (specific gravity, grain size), and fluid parameters (density and viscosity). Therefore, by Using the Buckingham theory and after eliminated the parameters with constant values, the important parameters were q/Q, D/h , Fr and α.Three-dimensional (3D) velocity components were measured using the electromagnetic velocity meter JFE ALEC model ACM3-RS in tests with and without an installed non-phase hydraulic jet. The sampling rate was 20 Hz and time of sampling was 60 seconds. So the minimum 1200 data were collected for each point and their mean was used for determine the 3D flow pattern. The results showed that with installing non-phase hydraulic jet, the maximum scour depth is reduced as much as 77%, 82.7% for Froude numbers equal to 0.37 and 0.41, respectively. It was also found that generally the scour depth occurs away from the outer bank and it was shifted toward the middle parts of the section in the main experiments, which can positively result in the increase in the navigable width and also sediment deposition was observed at the outer bank in some experiment. The results show that non-phase hydraulic jet significantly modified bed topography and reduced the maximum scour depth in outer bank. In this paper to evaluate the effect of space between porous tube and outer bank , three different space (D=0,2.5 and 8 cm) were used. It was found that by decreasing the space between outer bank and porous tube the amount of scour decreases and the maximum scour depth reduced as much as 87.9%, 54.5% and 15.15% for space equal to 0, 2.5 and 8 cm, respectively and it is most efficient when it placed on outer bank. Maximum scour was usually saw near the outer bank, and attributed to the maximum stream wise velocities that occur near the toe of the bank , also the analysis of data have shown that the presence of non-phase hydraulic jet caused uniformity in the velocity distribution at upstream and the high velocity zone moved toward the center of the channel and inner wall. The installing a non-phase hydraulic jet on the outer bank of bend, by its rising velocities, generated a secondary flow that rotates in the sense opposite to the curvature-induced secondary flow. The jet-induced secondary flow cell causes an inwards shift of the cores of maximum streamwise velocity and maximum vertical velocity impinging on the bed, that both of them play an important role in the cour in the outer bank.

Embankment weirs are finite crested weirs with various side slopes that can be used for different purposes such as flow measurement and diversion, water level management, aeration or water purification, etc. The hydraulic performance and the characteristics of flow over solid weirs with finite crest length in free and submerged flow conditions have been of interest to many studies (Azimi and David. 2013). Unlike the impermeable weirs, porous weirs contribute to the water purification in the rivers and channels downstream of the structures. Hence, they are structures with positive impact on water treatment. Sargison and Percy (2009) studied the performance of BC weirs with side slopes varying between vertical positions to 1V:2H. Results indicated that by decreasing the slope of upstream face, the discharge coefficient increases and the height of the upstream water surface reduces. Although the characteristics of flow over porous weirs have been studied until now, there are still remaining facts to discover about performance of these kinds of structures in practice. Hence, this study has benefited from extensive experimental data obtained by laboratory tests to develop formulas to estimate hydraulic parameters for discharge reduction factor in the submerged flow conditions. This study investigates the hydraulic performance of flow over the porous embankment (PE) weirs for both free and submerged flow conditions. To do this, the hydraulic behavior of flow over 16 different PE weir models was examined in a rectangular flume. Results showed that the effect of the upstream slope of weirs is negligible on the modular limit index while the downstream slopes of weirs did not affect the free flow parameters. Also, both up- and downstream side slopes have no significant effect on the characteristics of the submerged flow.

Any structure that is in the flow path and establishes a simple, specific and definite flow relationship and depth around it is called a flow controller. Weirs are structures that raise the water level behind them and create control sections and are simple means of measuring discharge. Bazin & Schwalt (1898) were the first to conduct experiments on rectangular broad crested weirs. Since then, many researchers have done a great deal of research on a variety of weirs. Among them we can mention: Woodburn (1932), Tracy(1957), Smith(1959), Abou-seida & Quraishi (1976), Hager&Schwalt (1994), Sargison & Percy (2009),….Due to the importance of flow measurement in open channels, the purpose of this study was to investigate the hydraulic performance of inclined weir, to determine the discharge conveyancecoefficient in this kind of structures in free and submerged flow condition, and to provide relationships to predict the discharge conveyancecoefficient.

Based on Equation 1, we can determine the weir discharge. In this equation Q is the discharge (m3 / s), Cd is the discharge coefficient (no dimension), B is the weir length (m), g is the acceleration (m / s2), and H is the height of the water over the weir (m).Also rewrite from the equation 1 to form 2 by defining it   as the discharge conveyancecoefficient (Mohamed, 2010):In this study, the equation 2 is based on the calculation of the discharge throughput on weirs. The following two equations for free and submerged flow are presented using dimensional analysis.The experiments were conducted in a plexiglass flume (Fig. 1) made of the British ArmField Company with a length of 15 m, a width of 30 cm and a height of 50 cm. A total of 60 experiments (30 free-flow and 30 submerged-flow experiments) were performed on the inclined weir.

A) Free flow condition
In this series of experiments, with increasing H/Lw ratio, the discharge conveynce coefficient of all three sloping weirs increased, but the coefficient of conveynce discharge of rectangular broad crested weir decreased (Fig. 1). This figure shows that among inclined weirs are most sensitive to H/Lw changes.Also comparison of the inclined weir with the rectangular broad crested weir indicates that the rectangular broad crested weir later is less sensitive to H/Lw. Equation 5 was derived to calculate the discharge conveyancecoefficient (Cf) in inclined weirs under free-flow conditions. B) Submerged flow conditionMultiple regression was used to investigate the interaction of the extracted dimensionless parameters on the discharge conveyancecoefficient and to provide a mathematical relation to predict these values. Equation 6 was derived to calculate the Cs coefficient in inclined weirs under submerged flow conditions. Figure 2 shows the computational and observational Cf, Cs in free and submerged flow conditions. The scattering of these points relative to the 45 ° line shows that the correlation coefficient of the experimental and computational values for free and submerged flow are equal to 0.9 and 0.91 respectively.

The results show that:- Increasing in H/Lw ratio leads increases in discharge conveyance coefficient of all three sloping weirs and decreases in rectangular broad crested weir. - For a constant value of the H/Lw ratio, the highest discharge coefficient is related to the upstream and downstream slope weir model (SCW-UD-1) and the lowest discharge coefficient is to the upstream slope weir model (SCW-U-1).-The upstream and downstream slope weir are most sensitive to H/Lw changes and rectangular broad crested weir is less sensitive to changes in H/Lw ratio. - As the H/p < /em> ratio increases, the discharge conveyance coefficient of all three sloping weir models increases.

Weirs are usually constructed by concrete and are impervious so that the water can only flow above the crest. In this between, Gabion weirs with instinctive characteristics including stability, conductivity and economic justification are strongly advised. In this study, the effects of material size, upstream and downstream slopes were investigated on the discharge reduction factor of gabion crump weirs under submerged flow conditions. For this purpose, 8 models of gabion weirs and 3 models impervious weirs constructed in a horizontal flume with 15m long, 0.3m wide and 0.5m deep. The tests were carried out for different variables, including discharge, upstream and downstream depths, material size and upstream and downstream slopes. The results showed that the flow reduction factor decreased as the ratio of the upstream depth to the downstream (Y2/Y1) increased. For a constant ratio of Y2/Y1, the flow reduction factor decreased when upstream or downstream slope increased. It was found that the material size has no significant effect on the flow reduction factor. Based on regression analysis, an empirical equation was developed for estimation of the flow reduction factor which its correlation coefficient variation was in the range of 0.79 to 0.96.

Due to problems with on-site irrigation channels, such as occupying a high level of the land, a lack of suitable loan materials, and the possibility of dealing with multiple complications, the use of prefabricated channels is one of the most competitive options available for the  existing channels. From the theoretical point of view, the most effective hydraulic cross-section for the coated channels in which smooth water flows is the semicircular section. Nevertheless, in terms of implementation, the use of the semicircular cross-section is generally limited to the reinforced concrete channel. One of the important issues in outdoor hydraulic engineering is having sufficient knowledge about the amount of hydraulic resistance against the flow. The estimation of hydraulic resistance of the flow in open channels has always faced a serious challenge because of the presence of secondary currents and the vortex viscosity. The determination of the contribution of flow pipes in the bed and wall is faced with errors due to the effects of the walls on the maximum velocity position. Accurate prediction of boundary shear stress distributions in the open-channel flow is crucial in many engineering problems, such as channel design, the balance of energy, and sedimentation. Determining the exact bed and wall shear stress is important from a theoretic and applied point of view, for example, its role in scour and sedimentation studies and designing shield conservations.

Polyethylene pipes are widely used in pressurized water systems. In the design and interpretation of the ram-trapped signal for diagnostic purposes, viscoelastic behavior of polyethylene tubes should be taken into account.The aim of this study is to detect leakage, and experimental and theoretical comparison of pressure wave velocity and over pressure of transient flow in polyethylene pipes with different Reynolds number. To achieve the objectives of this paper, a physical model was developed in laboratory of the Faculty of Water Sciences Engineering of Shahid Chamran University of Ahwaz and developed two different models of control and a leakage system was and were conducted a number of water-hammer tests. The leakage accuracy in this model increased with increase of Reynolds number. The highest and the lowest percent of the relative error for computational and experimental leakage were estimated 48.8% and 2.02 through a leak hole of 5 mm for experiments with Reynolds numbers of 1282.76 and 12973.55, respectively. Also, this inaccurate study shows the relationship between the theory of compressive velocity and overpressure in the polyethylene transfer pipes, so that the compressive velocity obtained from theoretical relationships is less than its actual value, as well as the relative error of the overpressure in leakage experiments Increasing the Reynolds number increases between the amount of the laboratory and the theory.

The flow from the dam is a tremendous amount of energy in the absence of energy dissipation, the flow through the irreversible damage to structures downstream of the dam. A one way of dissipating the excess energy is falling jet in the plunge pool. Flow jets in special distance have a dense core which formed of water particles. Much of the pressure on the bed and pool wall is caused by that dense core. After passing some distance, air Intrusion from border and flow turbulence causes to shrinking core and finally it will be vanished. This study examines the failure of the jet length and the parameters affecting it are discussed. Percent from the second to the third experiment the Froude number, approximately 15 % decrease and finally tests the third quarter increased 17 percent compared to 6 percent of the Froude number increases. So we can conclude that the changes failed to increase the jet flow (Froude number) is not constant after reaching a minimum point of the process increases. Further statistical analysis was determined according to the coefficient of expansion Jets in turmoil with the failure probability 0.1 is significant.

Measuring flow discharge in open waterways has always been one of the most important concerns for water experts. Flow surface image velocimetry method as a non-contact option has recently been widely utilized to measure discharge in open channels. One of these methods is a type of PIV method named LSPIV which has been paied more attention due to the elimination of laser application. In this study, LSPIV was used to measure 2D velocity field over the surface of a steep supercritical flow. Totally 24 experiments including three different slopes (2, 6 and 10 percent) and eight different dimension ratios (7 to 20.5) were conducted and in each experiment the flow surface was recorded with a frequency of 125 fps for 60 seconds. The Velocity Index was calculated bt the obtained velocity data. This index is used for convering the surface velocity to average velocity of the cross section and subsequently for determination of flow discharge. The effect of different dimention ratios on VI was investigated. The average value for VI was obtained to be 0.701 which is differ from the established value (0.85) by about 17%. Moreover, the flow surface time-averaged velocity patterns were quantitavely compared for different flow conditions. Since, the velocity index has been so far studied for subcritical conditions, the results of this study may be helpfull for measuring supercritical flows.

Destruction of bridges caused by scour and other natural phenomenon brings about financial and life losses. Hence, researchers have been studied extensively the scour mechanism and methods of scour countermeasure. Usually scour at bridge occurs both around piers and abutments. Melville (1992)'s study showed that 70 percent of the failure of bridges in New Zealand was due to the abutment scour. Studies conducted on the failure of 383 bridges in the United States showed that in 25% of them the pier scour, and in 72% of them the damage was due to abutment scour (Kayatrak, 2005). The main cause of the abutment scour is due to complex flow vortices which developed around the abutment. Therefore, during the past decades many measures have been developed to protect the bed material against erosion. These techniques can be categorized in two types of covering methods and flow altering techniques. Design guidelines for some of these mitigation techniques can be found in Melville and Coleman (2000). For existing bridges the common practice is to use armoring materials around bridge abutment. Riprap, gabions, rectangular concrete blocks and tetrahedron frames concrete elements are the most effective material for covering and stabilizing the bed around the bridge abutments. In rivers with high flood discharge, the covering material are subject to high flow velocities and therefore large size of rocks have to be used. When the site construction is far away from mountain area or large sizes of the rocks are not available or too costly to transport, other material should be applied. In the present study, a new concrete element-six –legs concrete (SLC)- beside using of smaller size of rocks have been studied to find out the best combination for protecting bridge abutments against scour.

An air-bubble screen is an innovative technique for riverbank protection along the bends which improve the navigation conditions in the alluvial rivers. In this research, the effects of this structure on a 90° mild and long bend on the bed morphology and flow pattern have been investigated. To this end, the experiments were carried out with three angles 0, 45, 90 degree and four Froude numbers of 0.37, 0.41, 0.45, 0.47 combined with three air discharge. Experiments performed in a mild bend using clearwater showed that the bubble screen was able to redistribute the velocity patterns and bed morphology in the bend. In addition, the results showed that maximum bend scouring is reduced about 47% andoccurs further away from the outer bank and high velocity zone shifted toward the center of the channel. The results showed that the maximum and minimum scour depths in outer bank with 0 and 90 degrees angles respectively. Also, by increase of air discharge ratio the maximum scour depth was decreased.

The present research deals with the introduction and simulation of viscoelastic effects in transient flows in polymeric pipes widely used in pipe network. The viscoelastic properties result in appearing newterms in transient flow governing equations which are generally absent in available models. In this study, the governing equations are rewritten and manipulated for considering the viscoelastic properties. The equations are then solved using the method ofcharacteristics coupled with the finite difference method. In order to calibrate the unknown parameters including the unsteady friction and creep coefficients as well as to verify the model, a model of viscoelastic pipe network was made at the hydraulics laboratory of Water Sciences Engineering department of Shahid Chamran University. The configuration of the experimental set-up consists of a pipe network with six square loops, having each loop 3m×3m. The pipes are made of PE with 50 mm nominal diameter and 5.5 mm of wall thickness. The data of dynamic pressure oscillation during these transient events were collected by Pressure transducers. Appling the inverse transient analysis method and with the aid of a genetic algorithm, the friction and creep coefficients of the experimental pipe are determined. The results show that the classical water hammer solver cannot accurately analyze the transient flows in polyethylene pipes. In fact, modeling both dynamic effects of unsteady friction losses and viscoelasticity for such pipes is quite necessary. However, it is also found that the viscoelasticity is obviously more effective than the unsteady friction effects in formation and attenuation of transient signals so that, considering onlyviscoelastic effects would result in acceptable responses.

Plastic pipes are widely used in pressurized water systems. The analysis of transient flow and estimation of maximum and minimum pressure wave propagation in pipeline and pipe networks is required for design and practice of piping systems, pumping stations, and dam water conveyance tunnels. The viscoelastic properties of the polyethylene pipes have significant effect on the estimation of pressure wave speed and attenuation in transient flow. The use of polymeric pipes such as polyethylene and polyvinyl chloride has recently increased due to their technical and economic advantages over steel and concrete pipes. Due to viscoelastic behavior, polymeric pipes have a significant impact on transient flows (Pezzinga, 2002). In a fast transient flow event like water hammer, viscoelastic properties of polymeric materials cause a residual stress in the pipe wall. These deformations will not return to their original state immediately after unloading (Covas, 2003). This viscoelastic behavior also affects the intensity, shape, and dampening of pressure oscillation in transient flows.
Covas (2003) developed a numerical model to simulate the viscoelastic behavior of the pipe wall in transient flow events. In this study, the results of a linear viscoelastic model were compared with experimental results in the presence and absence of unsteady friction loss. Soares et al., (2008) also considered transient flow in PVC pipes, and their results were in good agreement with those obtained by Ramos et al. (2004). Evangelista et al., (2015) studied water hammer phenomenon in a Y-shaped system both experimentally and numerically. According to their results, the linear viscoelastic model was able to simulate the water hammer phenomenon in this system.
The present research deals with the introduction and simulation of dynamic effects, including unsteady friction and pipe-wall viscoelastic in transient flows in polymeric pipes that widely used in water works. Accordingly, the governing equations are rewritten and manipulated for considering the unsteady friction and viscoelastic properties. The equations are then solved using the method of characteristics coupled with the finite difference method. Appling the inverse transient analysis method and with the aid of a genetic algorithm, the unknown parameters are determined. Steady state friction coefficients have to be estimated based on steady state data and other unknown parameters were calibrated based on the transient flow.