مقالات رزومه دکتر منوچهر فتحی مقدم

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.

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.

During the recent years, Gabion weirs have been taken into consideration due to their compatibility with the environment, positive effect on river’s water quality and their simple design and implementation. In this research, the Hydraulic parameters of flow around broad crested gabion weirs (BCGW) with various side slopes are investigated. Overall, a number of 21models comprising 7 various geometries each with 3 different porosities including (43%, 44% , 46%) and in 10 to 6 different discharges were simulated and studied. Results indicated that the discharge coefficient (Cd), through flow discharge and energy dissipation increased by increasing the average diameter of particles. In addition, Increasing the area of the porous media by changing side angles from 0ᵒ to 60ᵒ reduces the dischrge coefficient and through flow discharge. At final stage, experimental equations are presented using Nonlinear Multivariable regression analysis in order to calculate the discharge coefficient and through flow discharge of these structures.

Stilling basins are the most common structures for energy dissipation downstream of spillways. A properly designed stilling basin can ensure 60–70% dissipation of energy in the basin. The purpose of this study is to evaluate the performance of perforated end sill and effect of the sill on characteristics of hydraulic jump. The perforated sills with different heights and four ratios of opening 12, 25, 50 and 75% were tested for three tail water depths. Results of experiments confirmed significant effect of the perforated sill on dissipation of energy, reduction of the basin length and reducing dependence of jump location on tail water depth. Based on experimental observation, in a constant Froude number, decreasing of the tail water depth causes the hydraulic jump to move forward toward the end of the basin. In this case, to control the jump and to avoid the hydraulic jump being swept out of the basin, sill distance is decreased. Also, observation showed the sill height needs to be increased as inflow Froude number increases and tail water decreases. In the other words, relative sill height increases up to 30% as tail water depth ratio decreases from 1 to 0.8. Furthermore, the results showed that sills with the 50% opening in comparison with other openings have most effective in energy dissipation and reduction of the hydraulic jump length. The comparison of stilling basin with perforated sill and free jump indicated that the sill with perforation ratio of 50% dissipated 60–90% of water energy in inflow Froude number range of 4.5-12. Moreover, once Froude number increases from 4.5 to 12, stilling basin length increases about 19% for this perforated sill in the tail water depth ratio of 1.

Plunging pools are constructed at the downstream of dam spillways to dissipate the excess energy. The turbulent flow velocity converts to the dynamic pressure due to impact of flow with the pool’s bed. The aim of this research is to determine impact pressure of a vertical jet on plunging pool bed. Hence, the experiments were carried out in four different discharges (ranging from 6 to 27.5 lit/s according to the nozzle diameters), three jet diameters including 4.3, 5.2 and 8.2 cm and four falling heights of 37, 60, 90 and 120 cm. Also the experiments are conducted in similar flow conditions for smooth and rough surfaces, and results are compared. Dynamic pressures were measured with a pressure transducer. The analysis of data showed that increase of jet diameter causes decrement in the dynamic pressure coefficient. Results revealed an increase in dynamic pressures due to roughness of contacting surface. Moreover, variations of jet Froude number and fall length have significant effects on the dynamic pressure coefficient. The impact pressure was the highest in the surface center and was gradually reduced in outer zones.

Transient flow is generated by an instantaneous reduction in flow rate due to rapid valve closure or pump failure in a water network. Transient flow creates high and low pressure waves that it may be to damage pipelines. Comparison of experimental and numerical results in previous studies revealed that quasi-steady models with assumption of uniform and 1D velocity profile could not correctly predict the damping process of the pressure waves. So¡ the aims of this study are investigation of velocity profile at the downstream end section of pipeline to give a correct understanding of transient flow dynamics. Also¡ this paper evaluates the ability of the instantaneous acceleration–based (IAB) unsteady friction models to estimate pressure history in transient flow using the method of characteristics. To achieve this goal¡ a pipeline¡ made of PVC¡ with a nominal diameter of 63 mm in the two different lengths of 40 m and 80 m was used. In addition¡ a ball valve at the downstream end was installed to create transient flow. The data of velocity distribution and dynamic pressure oscillation during these transient events were collected by Ultrasonic Doppler Velocimetry and Pressure transducers. Results of experiments indicate existence of inflection points in the base flow velocity profile and the large velocity gradient near the pipe wall. Furthermore¡ the results show that two-coefficient models produce a better match with the experimental measurements. The terms Vt and Vx in unsteady friction models affect the phase shift and the damping of transient pressure waves¡ respectively. Moreover¡ the coefficients of acceleration terms vary from 0.0037 to 0.006 for kt and from 0.0325 to 0.052 for kx.

Wave attack is the main source of irreparable damages to the sea coast line. The coastal protection techniques are now improved from structural protection to biological ones. This includes plantation of trees and development of vegetation canopy (called green belt) along the shorelines and protection of coastal structures against the waves created by tsunami. For this¡ the application of green belt has been studied and effect of vegetation density and wave height on wave force is evaluated for waves in broken condition. Experiments were conducted in a flume with 8.3m length¡ 0.8m width¡ and 0.55m height. Experimental variables include four bed slopes¡ four vegetation densities¡ and 110 wave heights. The results show that absorption of wave force increase with increase of wave height and density of vegetation. At the highest vegetation density the wave force effect was reduced by about 75% compared to the case without vegetation.

Talog Dam located in Khuzestan province plays an important role in power generation and water supply of the region. Some studies are performed on this dam. These studies produce Artificial Time Series and accurate estimates of inflow to the dam which will have an important role in water resources planning in the future. In this study, using the statistics estimated Talog river at the dam site Talog, stochastic modeling was performed for both of them. Various stochastic models such as Autoregressive Model (AR), Moving Average (MA), and Autoregressive Moving Average (ARMA) were fitted to the data. According to the Akaike and Schwarz information criteria, the results of Modeling showed that ARMA model (2,3) was the best model in comparison with the other models. Therefore, according to the selected Model, five artificial time series and forecasting future time series for the model were performed the results of which are presented in the present study.

Creation of transient flow in closed conduit is a common phenomenon and also causes serious damage in water supply systems. Flow path leads the system to design of pipes in contraction and expansion series and also gradual and sudden changes in the cross-sections. These changes create negative pressures in pipes specially where pipe diameter changes. The main purpose of this study is experimental investigation of pressure-wave changes in pipes in contraction and expansion series specially where the diameter changes. Tests were carried out with different speeds of valve opening and the results showed that in pipes in contraction series، changes of pressure-wave speed due to pressure changes (that resulted from the opening of the valve at the downstream end of the piping system)، at the locations where the diameter changes was more than sections near the valve.

Local scouring immediately downstream of stilling basin is unavoidable when a local velocity exceeds incipient motion. This phenomenon causes a difference in the level of basin concrete bed and natural river bed that is turn affects the rate of scouring. In this study hydraulic model of Namrood dam was used the experiments. Results of this study showed that the stable stone size increases with a reduction of tail water, promotion of critical depth and the level of degradation. Having discharge and tail water depth, the developed relationships in this study could be used to estimate the size of stable stone for any level of degradation