جستجوی مقالات مرتبط با کلیدواژه « سرریز » در نشریات گروه « آب و خاک »

Side weirs are important structures in irrigation and drainage networks that are used as a protective structure upstream of reverse siphons and road underpasses. In this research, using laboratory data, for two positions of lateral overflow placement diagonally in the width change wall and directly and in the wall without change width, a new relationship based on the critical depth of flow on the weir to determine the discharge discharge weir (QW) are provided in rectangular channels with narrowing downstream of the weir. The results showed that the discharge capacity of oblique weir decreasing width downstream is more than normal overflows and also diagonal weirs located in the width reduction wall are more than the case where the weir is in the direct wall without width reduction. Finally, by comparing the relationships obtained from dimensional analysis in two types of overflows, it can be concluded that the flow rate of side weirs located in the diagonal wall of the transition section is about 7.50 percent higher than the case where the side is located in the direct wall of the weir. The reason is less interference of flow lines. Also, the narrowed part of the downstream acts as a barrier, increasing the depth of flow and less curvature of the flow lines, and the flow passes through this weir with less drop.

After Hamidieh Diversion Dam near the city of Hamidieh, Karkheh River is divided into two streams known as Hufel and Nissan. At the lower flow rates, Nissan makes up a greater share than Hufel due to the steeper slope of the former. This study attempted to construct a hydraulic structure to appropriately divide water flow in Hufel. In a laboratory experiment, a flume with a 90-degree bend was used at Islamic Azad University of Ahvaz. Various experiments were conducted at different widths and heights. Furthermore, this model was simulated through CCHE2D, the results of which were compared against those of physical and mathematical models. The results indicated that the weir height increased the deviation flow percentage to the Hufel stream due to rising water level. Moreover, the deviation flow percentage to Hufel was declined as the weir width was increased due to falling water level. At Hufel, the installation of rectangular weir in different dimensions yielded the minimum of 34.3% and the maximum of 61.5% increase in the flow rate. In the normal mode without any weirs installed, however, there would be an increase in the flow rate, as compared to the mode where a weir has been installed. This can be associated with the flow controlled by the weir. On average, the deviation flow rate was increased by 2.8% in the weir mode and 7.7% in the weir-less one. An increase in the Froude number from 0.21 to 0.38 led to a lower average deviation flow rate by 19.3%. Moreover, the results of the simulation through CCHE2D were demonstrated to be largely similar to those of physical model experiments. However, an increase in the Froude number did not lead to a decline in the deviation flow rate (i.e. it remained constant). This trend was inconsistent with the results of the physical model.

weirs are widely used to measure flow, water deviation and flow control in open channels. So far, most of the weirs used in the diversion dams were linear. In this study, the effect of sediment properties transmitted in the main channel and intake channel has been studied by changing the magnification of the weir.

The research was carried out at the Hydraulic Laboratory of the Water Engineering Department of Bu-Ali Sina University. The experiments were carried out in flume lengths of 10 meters, width of 83 cm and height of 50 cm. weirs, gate and intake channels with accessories and reservoir of sediment collection were also designed and added to the collection. For testing, non-adherent sediment particles with a grain size of approximately the same size and with a diameter of 0.35 mm were used. Experiments were carried out with a layer of sediments of thickness of 4 cm and slope of 0.002 and in two discharges of 40 and 60 liters per second. At first, intake gate and sluice way was closed and a flow with a small discharge entranced until the flow passed on the weir. Then the discharge increased to 60 or 40 liters per second. Then the intake gate was opened to a certain amount and the experiments were carried out for a certain period of time. Then, the entered sediments into the intake channel and also the accumulated sediment in the mesh of the end of main channel were collected, dried and weighted, and the concentration of sediments entering the intake channel and also downstream of sluice way were calculated.

The results showed that, in equivalent intake discharge ratio, with increasing discharge from 40 liters to 60 liters, the concentration of sediments in the intake channel increases. Also in equivalent intake discharge ratio, increasing the weir magnification increases the concentration in the intake channel. Also the increase in intake discharge ratio and the increase of the sluice gate discharge ratio, increase the concentration of sediments in the intake channel. The same applies to the sluice gate. This means that increasing the magnification, increasing discharge, intake discharge ratio and sluice gate discharge ratio will increase the concentration of sediment input to the intake channel.

Increasing the magnification reduces the flow head and also reduces the flow depth in the upstream, and as a result, the shear stress rate of the flow increases, which results in the transfer of more sediment to the downstream and, consequently, to the intake channel. Increasing the opening of the intake gate and, consequently, increasing the intake discharge rate, also increases the concentration of sediments deposited to the intake channel, However, increasing the weir magnitude and also increasing the sluice gate discharge ratio has no Significant influence on the sediment concentration ratio of the canal intake to the main channel.

More than 75% of the rice cultivated land is located in the northern provinces of Mazandaran, Gilan and Golestan. In recent years, the second cultivation of rice has been developed. This research was carried out in Mazandaran province, Khazarabad region of Sari, for the Premature varieties of local Tarom during two seasons for second cultivation in (2016 and 2017). In this study, triplicate overflow was used to measure inlet and outflow discharges. Three lysimeter were used to determine the water requirement of the fields. The water requirement was calculated from the input difference, which included the amount of water input that was calculated by overflow, as well as rainfall and output, including (evapotranspiration, permeability of the lateral submerged area and drainage water) Also, the irrigation of three stages of crop, reproductive and rearing for the first crop of (2015) was estimated to be 1.10, 1/5, 1/2 The coefficient for the second cultivation of (2016) was ./98, 1.4, 1.03, and the second planting factor of 2017 was ./95, 1.34, 1/01 respectively. The results show that the amount of water requirement in the second cultivation of 2016 and 2017 is 33%, 27% less than the first crop of 2015 respectively. Also, the average of crop factor in three stages of growth in the second cultivation of 2016 and 2017 was 10% and 12%, respectively, compared to the first one of 2015. Therefore, in regions where there is a good level of rainfall during the second crop, it is possible to recommend the second crop of rice.

Considering the drought crisis and high consumption of water in paddy fields, it is useful to present strategies in order to increase irrigation efficiencies. However, one of the methods to increase productivity in the agricultural development of cropping and ratoon culture that has an important role in the economy of rural households. Therefore, it is necessary to determine the amount of water needed for the second cultivation of rice and the cultivation of ratoon for water resources planning. This study was conducted in Mazandaran province, Sari. The local Tarom early varieties during two crop seasons in 1395 and 1396 years of regional ratoon also was conducted in 1396. To measure the input and output flows, triangular overflow was applied to the treatments and three lysimeters were used to determine the water requirement of the fields. Water use efficiency and water productivity were investigated in each treatment season. The results showed that the highest consumption efficiency was measured at 61% in ratoon cultivation. The water use efficiency in ratoon cultivation increased by 39% compared with the second cultivation of 1395 and 42% compared to the second cultivation of 1396. Water productivity in the second cultivation of 1395 and 1396 and ratoon cultivation in 1396 was 51%, 33% and 40%, respectively. Therefore, in areas with enough rainfall during the second cultivation and cultivation of ratoon, second cultivation of rice and rattan culture can be recommended.

Spillways are structures used for releasing the surplus floodwater in necessary conditions from storage dams. Ogee spillway is one of the most common and simplest structures. . In this research, a three dimensional flow field over the spillway was simulated with Flow-3D, using two turbulence models, namely RNG and . First, for precise prediction of hydraulic specifications of over spillway flow, the mentioned turbulence models were validated using data gathered from a laboratory flume (Sivakumaran et al., 1983). Data collected from software validation showed that the RNG turbulence model produced better results than . In the next stage, this model was used for simulating the physical prototype of the Nimrod Reservoir Dam. The measurement factors included pressure and water surface profile. The obtained values were compared to the existing laboratory measurements. Results from the simulation were well consistent with experimental measurements.

In places where the flow velocity is high, due to the unevenness of the spillway bed , the streamlines are separated from the bed, and at the downstream area, the pressure drop occurs and ultimately leads to the destruction of the spillway bed (Raesi, 2011). Jonson (1963) showed that, if the vacuum is formed inside the vortex core, the initial value of the vacuum should be less than or equal to one. Ohern and Katz (1986) have shown in their research that the beginning of the initial vacuum is in the three-dimensional structure inside the nucleus and not in the nuclei of the circuits. Savage and Johnson (2006) have found that a numerical model is useful for determining the flow rate and flow pressure by comparing the numerical and physical model of the flow over the Ojee spillway. Zhang, Wu and Dong (2010), with the help of the model made in the Hydraulic Laboratory of the University of Zhijiang, have studied the effect of air mixture in flow on the surface pressure and vacuum, and showed to have a positive effect on air concentration. ShafaiBajestan and NasrEsfahani (2014) investigated the cavitation phenomenon at the stilling basin with a rough bed and an abrupt drop. In this study, factors affecting the index of cavitation like velocity, pressure and the amount of air into the stream in five states of without aeration, with ramps on the bed, with ramps on the bed and wall duct, with a ramp in the walls, and also with a ramp on the bedand the wall was examined.

draining the flood of enormous dams and transmitting the procedure to the downstream is one of the important issues regarding hydraulic structures. Plunge pools are the main structures to dissipate the high rate of energy. The amount of energy at an outlet jet depends on various parameters such as the dropping height, the thickness of the jet, and other environmental conditions. Local erosion in plunge pools with alluvial beds is a complex phenomenon and determining the geometric features of the scour hole is really difficult. The outlet flow mixes with the turbulence factor and hits the bed of the plunge pools with a semi-perpendicular condition. Therefore, the present study was conducted to determine the scour which was caused by inlet air along the middle water jet on the bottom of the plunge pools. Xu et al. (2004) tested the aeration effects on the scouring caused by the falling jet and obtained a small relationship between the percentage of air jet density and the relative scour depth. The results informed that aeration affects the shape of the scour hole and essentially reduces the scour depth. Manso et al. (2004) investigated the interaction of the geometric shape of the submerged pond with rocky bedding on the rate of diffusion of the falling jet. They tested various diameters of jets,5.5, 11 and 16.5 times the diameter of falling jet, on the smooth and rough beds to investigate the dynamic pressures with frequencies between 1 to 2 KHZ. Their findings showed that the geometric shape of the pond has a direct impact on the jet diffusion rate. Duarte et al. (2015) studied the effects of air inlet to jet on the dynamical pressure on the floor of the submerged pond. They increased the jet's velocity to 22 m/s. The final results showed that the air inlet to the jet led to a decline in the total pressure on the floor of the pond.

The combination of weir and gate creates a new structure, resolve some the defects of using them separately, such as the simultaneous flow pass of deposits under gate and suspended material over the weir, also benefits the ability of vertically movement and making different gate openings according to the changes of the discharge, control the water level more accurate and adjust constant head of water for the side channel. Likewise, the cylindrical weir-gate, as one the weir-gate’s type, has various advantages like higher discharge coefficient and lower energy loss. Researchers have been conducted on the hydraulic aspects of this structure state that the discharge coefficient of combined model of cylindrical weir-gate (discharge coefficient is the most important hydraulic parameter of designing the weir-gates), decreases in each parts of weir and gate, regarding to their separated function. On the other hand, in addition to effective hydraulic parameters on discharge coefficient, extensively have been studied by previous researchers, hydrodynamic phenomena such as flow separation, vortex shedding, the convergence point of shear layer passing through the both sides of the structure and etc., resulting from the assumption of hydrostatic pressure on the structure body, play a crucial role in discharge coefficient, discharge rate and other flow characteristics. Therefore, in order to investigate the changes of separation points under and above the structure, the convergence point of boundary layer of the both sides, velocity distribution above and at the downstream of the structure, as well as the size of the wake with gate opening, a series of runs using the technique of particle imaging velocimeter (PIV) were carried out, and the results were analyzed.
The experiments were conducted at the hydrodynamics laboratory of mechanical engineering department of Çukurova University using the PIV technique on a cylinder with a diameter of 50 mm for five different relative gate opening between 0.1-0.5 (ratios of the gate opening to the cylinder diameter). Besides, for all the tests, the upstream water depth and entrance velocity were constant:150 (mm) and 0.58 (m/s) respectively.
Results and The results show for all ratios of the diameter to gate opening, the separation point of flow from the body of the structure was different in function as gate and weir parts and the separation occurs earlier as gate, so that, at the test range, the maximum and minimum of the separation angle’s deviation of the weir and gate were40 and 3 degrees. As the gate opening increases from 0.1D to 0.4D, The horizontal distance between the convergence point of two separated boundary layer to structure would be less. As well, the gate opening increasing cause fluctuations in vertical direction of the convergence point, the convergence point (S), in the opening range of the current study, had the vertical deviation between 0.1 to 0.15 D to horizontal axis crossing the cylinder center and locates under the axel in all cases. The velocity profile along the X-axis (u/Uo) and (v/U0) Y for all the gate openings to a distance equal to the diameter of the structure behind of it, is strongly affected by hydrodynamic factors. Above the weir-gate while the angel increase from 0 to 90 degrees, the ratio of maximum velocity to the entrance velocity rises, so that, at the crest level and increasing about 27 percent compared to the zero point could be observed, but in the higher levels, exhibits fluctuation and this fluctuations in the gate opening equal to 0.5D causes the dimensionless value of maximum velocity to entrance velocity near the separation point is about 17 percent compared to values obtained the crest level.

The circular weirs are one kind of broad crested weirs that have some advantages such as being economic, simple designing and high discharge coefficient in comparison with the other alternatives. High curvature of the stream lines over this kind of weirs is one of affecting factors on the discharge coefficient. The study of discharge coefficient in the circular weirs, due to changes of hydraulic conditions, is very important in the design and application of these structures. In this research, the flow has been studied over 3 groups of circular weirs with diameters 6.3, 9.0 & 11.4 cm, using the numerical model of FLOW-3D. Further, the method of finite volume was used to solve the extant equations and the model of RNG was also used to investigate the flow turbulence. The results have been presented as velocity profiles and discharge coefficient which was calculated for different discharge rates. The results of this numerical model were compared with experimental results for these groups of circular weirs, and a proper agreement has been observed between them.
The circular weirs are one kind of broad crested weirs that have some advantages such as being economic, simple designing and high discharge coefficient in comparison with the other alternatives. High curvature of the stream lines over this kind of weirs is one of affecting factors on the discharge coefficient. The study of discharge coefficient in the circular weirs, due to changes of hydraulic conditions, is very important in the design and application of these structures. In this research, the flow has been studied over 3 groups of circular weirs with diameters 6.3, 9.0 & 11.4 cm, using the numerical model of FLOW-3D. Further, the method of finite volume was used to solve the extant equations and the model of RNG was also used to investigate the flow turbulence. The results have been presented as velocity profiles and discharge coefficient which was calculated for different discharge rates. The results of this numerical model were compared with experimental results for these groups of circular weirs, and a proper agreement has been observed between them.
The circular weirs are one kind of broad crested weirs that have some advantages such as being economic, simple designing and high discharge coefficient in comparison with the other alternatives. High curvature of the stream lines over this kind of weirs is one of affecting factors on the discharge coefficient. The study of discharge coefficient in the circular weirs, due to changes of hydraulic conditions, is very important in the design and application of these structures. In this research, the flow has been studied over 3 groups of circular weirs with diameters 6.3, 9.0 & 11.4 cm, using the numerical model of FLOW-3D. Further, the method of finite volume was used to solve the extant equations and the model of RNG was also used to investigate the flow turbulence. The results have been presented as velocity profiles and discharge coefficient which was calculated for different discharge rates. The results of this numerical model were compared with experimental results for these groups of circular weirs, and a proper agreement has been observed between them.
The circular weirs are one kind of broad crested weirs that have some advantages such as being economic, simple designing and high discharge coefficient in comparison with the other alternatives. High curvature of the stream lines over this kind of weirs is one of affecting factors on the discharge coefficient. The study of discharge coefficient in the circular weirs, due to changes of hydraulic conditions, is very important in the design and application of these structures. In this research, the flow has been studied over 3 groups of circular weirs with diameters 6.3, 9.0 & 11.4 cm, using the numerical model of FLOW-3D. Further, the method of finite volume was used to solve the extant equations and the model of RNG was also used to investigate the flow turbulence. The results have been presented as velocity profiles and discharge coefficient which was calculated for different discharge rates. The results of this numerical model were compared with experimental results for these groups of circular weirs, and a proper agreement has been observed between them.
The circular weirs are one kind of broad crested weirs that have some advantages such as being economic, simple designing and high discharge coefficient in comparison with the other alternatives. High curvature of the stream lines over this kind of weirs is one of affecting factors on the discharge coefficient. The study of discharge coefficient in the circular weirs, due to changes of hydraulic conditions, is very important in the design and application of these structures. In this research, the flow has been studied over 3 groups of circular weirs with diameters 6.3, 9.0 & 11.4 cm, using the numerical model of FLOW-3D. Further, the method of finite volume was used to solve the extant equations and the model of RNG was also used to investigate the flow turbulence. The results have been presented as velocity profiles and discharge coefficient which was calculated for different discharge rates. The results of this numerical model were compared with experimental results for these groups of circular weirs, and a proper agreement has been observed between them.

Weir is one of the most applicable instruments for flow control and measurement in open channels. Accurate measurement of discharge in irrigation channels is vital for irrigation management. Weirs are designed as control sections for providing a unique relationship between the discharge and water head. In current study, theoretical and experimental characteristics of flow through a weir located in a horizontal circular channel were investigated. Choosing of this structure is due to lack of adequate studies on governing hydraulic equations of this kind of channels and its practical characteristics. In this research, discharge through the weir located at the end of a horizontal circular channel was developed from a theoretical viewpoint, and then calibration of this theoretical discharge equation was done via the discharge coefficient. The experimental data obtained in the study were also used to develop an empirical discharge coefficient relationship.
Theoretical discharge equation:The discharge equation of the circular weir ends up incomplete elliptic integrals of the first and second kinds, which are not very suitable for practical purposes due to their complexity. The theoretical discharge over the weir, Qt, can be expressed as:in which F(a,b) is approximated using the method of undetermined coefficients as:where g is the gravitational acceleration, h is the flow depth above the weir crest, D is the channel diameter, , , , and P is the weir height.
Introducing the discharge coefficient, Cd, yields the following equation for actual discharge, Q, of the weir.
Experimental setup and discharge coefficient equation: Determination of discharge coefficient, Cd, needs measuring the actual discharge (experimental or field data). The experiments were performed at the hydraulic laboratory of the Irrigation and Reclamation Engineering Department, University of Tehran. In order to collect experimental data, the weir was installed at the end of two horizontal circular channels with nominal diameters of 200 mm and 300 mm, and numerous measurements of different parameters that may have effect on discharge coefficient were carried out. An opening was provided on top of the pipes for flow head measurements by the point gauge. Water head over the weir crest was measured at a distance of 0.45 m upstream of the weir section. The weir plate was made of 10-mm-thick PVC sheet with a crest thickness of about 1 mm, and the downstream edge bevelled to a 45° angle (sharp-crested weir). For water heads over the weir crest smaller than 1.5 cm, in some cases clinging flow did occur and thus there was no atmospheric pressure under the lower nappe. Though, for heads greater than 1.5 cm a clear lower nappe profile with atmospheric pressure underneath was formed. Effects of surface tension and viscosity forces on the discharge coefficient, Cd, became pronounced at low water heads. Viscous and surface tension effects on discharge coefficient are neglected in this research. This is owing to operating range of the weir (minimum water head of 2 cm), which forbids surface tension effects and eliminates viscous effects. The experimental coefficient of discharge is computed for each data set collected in this study for known values of D, h, P and Q. A total of 350 tests were conducted to collect the data in the discharge ranges of 0.5 and 45 l/s. Suitable empirical equations for discharge coefficient were proposed using the 70% of the experimental data, and remaining data (30%) were used for validation procedure.
Proposed empirical equation for discharge coefficient: Using the curve-fitting technique, the following equation is obtained for CdThis empirical equation is valid for 0.095≤h/P≤1.8, 0.27≤P/D≤0.73 and 0.05≤h/D≤0.56. The assumptions made in deriving the above empirical equation of discharge coefficient are that the channel slope is horizontal, the flow is free and surface and viscous tension effects on Cd are negligible. A comparison of the experimental discharge coefficient with computed ones using the proposed empirical equation for all of the experimental data, the calibration data set and the validation data set showed that the computed discharge coefficient values are well within ±5% of the observed data for all three data sets. The average relative error of computed discharge coefficient using the proposed empirical equation for discharge coefficient Cd compared with the observed values is less than 5% for 95% of all experimental data. The results of this study reveals that a weir with low flow height is more sensitive to water flow depth, and weirs with more height are less sensitive to upstream flow head variation and thus are more reliable for flow measurement.

Abstract: The present research investigate experimental the head loss of flow energy throw the semi cylindrical wire-gates. The effective parameters on the studied system in forms of dimensionless parameters obtained by using Buckingham’s theory. The experiments were conducted in a rectangular flume with the length of 8m, width of 0.282m and height of 0.3m in Soil Conservation and Watershed Management Research Institute, using physical models with diameters 70, 120 and 160 mm in height of the opening between 0 until radius and differently discharging. The ratio of cylindrical structure diameter to channel width (D/B) was in the range of 0.25 to 0.57 and the Froude number was in range of 0.08 to 0.55. The results shows that in all angles which structure sets, dimension less parameter Hf/H cases curvature upstream and downstream with increasing Froude number and dimensionless parameter H/P increases, so that coefficient in both cases curvature upstream and downstream with increasing water depth upstream and dimension less parameter H/P Linearly decreases. Constant a (H/P) and Froude number, a dimensionless parameter Hf / H when the curvature is upstream semi cylindrical wire-gate due to the gradual contraction of flow lines and thus decrease the input is less than the curvature is downstream structure. Moreover, the result shows that in addition to the angle of semi cylindrical curvature to horizon line, structure diameter was affected on head loss amount.

Weirs are hydraulic structures that are built for regulating, controlling and diverting water in the flow direction. Gabion structures are used extensively in water projects due to the ease of construction, permeability, accessibility and economic efficiency. Porous gabion structures are adaptable to the environment due to their material and performance and also are valuable from ecologic view point. In this study, 8 physical models of gabion weirs and 2 models of solid weirs were built for determining discharge coefficient in gabion rectangular broad crested weirs. Comparisons between gabion weirs with solid weirs were done and they showed that the discharge coefficient in gabion weirs was greater than that in solid weirs. In addition, the regression relations based on the dimensional analysis for the flow through gabion weirs were obtained for both the free and submerged conditions. Results showed that the discharge coefficient of gabion weirs in free condition was 16.7 % greater than that of the submerged condition.

Because of the fairly simple equations for accurate flow measurement and controlling the water level, weir and gate method is more useful than the separate weir, gate and partial flume methods. Since the flowing water in the channel always contains sediment particles and floating debris, they are deposited at the gate inlets and behind the weirs which reduces the size of the channel in the structure range and which reduces some problems such as neighboring land flooding due to overflow of water from the channel banks, threatening the structure stability and reducing the measurement accuracy. Using a combination of weir- gate model, in comparison with other conventional devices, will make it possible to get the actual conditions closer two main hypotheses derived from the relations and accurately measure the discharge coefficient. In this model, the deposited materials are easily passed through the gates and the suspended debris are easily passed over the weirs. One of the combined weir- gate structures is semi cylindrical weir- gate structure. Regarding about the form of the combined weir- gate structures, it has some advantages , including simple design, sediments and floating material flow, high flow discharge coefficient compared with other replaceable structures and its being economic. Semi Cylindrical gate turning around center Axis, for reason of rotation the center becomes Conversion to wire, wire gate with opening with different height.
The experiments were conducted in a rectangular flume with the length of 8 m, width of 0.282 m and height of 0.3 m in Soil Conservation and Watershed Management Research Institute. In this research, PVC pipes were used as semi cylindrical gate structures. The experiments were conducted for three diameters 70, 120 and 160 mm with height of the opening between zeros until radius, angles zero, 30, 45, 60 and 90 degree and differently discharging. Experiments were performed at a discharge limit of 2-27 l/s. In order to decrease turbulence of the flow, the gate was installed at the end 4 m of the flume. The ratio of cylindrical structure diameter to channel width (D/B) was in the range of 0.25 to 0.57 and the Froude number was in the range of 0.08 to 0.55.
Coefficient discharge of semi cylindrical structure and then dimensionless parameters of [H/P], [a/H], [ /H] and [Fr] against the discharge coefficient in the studied gate opening between zero until radius were investigated. According to result with decrease dimensionless parameter of a/H, discharge coefficient increased, So that the maximum Coefficient discharge rate of angle 90 degrees and minimum angle 0 degrees. Also in a constant of a/H for the curvature of the downstream and upstream, with increasing the diameter of semi cylinder, discharge coefficient remains and has no change, shows that changes in diameter of semi cylinder have no significant impact on discharge coefficient. With increasing H/P for both curves upstream and the downstream, discharge coefficient increased. Also in a constant of H/P for the curvature of the downstream and upstream, with increasing the diameter of semi cylinder, discharge coefficient remains. With constant of angles with increasing Freud for all angles, both the curvature of the downstream and upstream, /H decreased. Also in a constant of Freud and angles, with increasing the diameter of semi cylinder, /H remains. According to the result, discharge coefficient of semi cylindrical gates varies, in Experimental limit, from 0.45 to 1.45 which is more than that of sluice gates reported by the USBR. One of the reasons, this is ascribed to this is the difference between the amount of entrance, head loss in this structure, because when the flow approaches cylindrical gate, due to curvedness of the wall upstream, a gradual gathering of flow lines gives the aerodynamic method to entrance section, thus decreasing resistance against the flow and entrance head loss and increasing discharge coefficient. However, in sluice gates the vertical wall in entrance section is conducive to fast gathering of flow line, thereby increasing resistance against flow, increasing entrance head loss, and decreasing discharge coefficient relative to a semi cylindrical method.
The results showed that increasing Froude coefficient and decreasing the a/H (ratio of gate opening to upstream water depth) dimensionless parameter decrease, respectively increase the discharge coefficient and decrease head loss in all aspects of structural alignment. Within addition by increasing the H/P dimensionless parameter (ratio of upstream water depth to structure diameter) discharge coefficient increased. Results showed that the maximum and minimum values of discharge coefficient are related respectively to 90 degree and 0 degree angle.

One of the common methods to dissipate energy of the flow passing over a dam is using flip bucket spillways to create free falling jet to the downstream. However, the collision of the falling jet to the downstream bed will cause topography changes due to scour threatening the stability and safety of the hydraulic structures. In case of precise analysis of the downstream topographic conditions due to the falling jet, such structures perform better than other dissipaters. Experimental results show that the dimensions of scour hole are dependent upon upstream water depth, discharge and tail water depth. Due to water and sediment flow complexities and the effect of different geometric-hydraulic parameters on bed profile variations, more studies are needed.In the present study, the effect of flip bucket tooth and upstream gate opening on downstream bed topographic changes due to falling jet was investigated using a flat flume having dimensions of 2m*0.5m*0.5m. The free falling jet was controlled using a sluice gate located upstream of the flume. Falling jet hit a downstream sedimentation basin having dimensions of 2 m long, 1.5 m wide and 0.7 m deep. Tail water depth was controlled using a gate located at the end of the sedimentation basin. Spillway and flip bucket of the Karoon III dam were modeled considering a 1.165 scale. Experiments were carried out on a normal (simple) and slotted flip buckets. Slot dimensions were selected as 2 cm according to USBR (1987) recommendations. To control the water surface level at upstream of the spillway for different discharges, a sluice gate was used at the spillway inlet. To investigate bed topographic changes, sedimentation basin was filled with non-uniform silica sediments with a mean particle diameter of d50=2.76 mm, the geometric standard deviation of σ=2.11 mm, uniformity coefficient of Cu=4.07 and a specific gravity of γs=1.52 gr/cm3 according to grading curve up to a depth of 40 centimeters. Researches show that several geometric-hydraulic parameters influence bed topography changes at downstream of the flip buckets. Most important parameters include input flow velocity to the flume (V), tail water depth (Yt), flow density (ρ_w), kinematic viscosity (μ), acceleration of gravity (g), specific or mean diameter of bed particles (d50), bed particles density (ρ_s), falling jet height from the bucket edge to sediment level (Hw), gate opening height (L), bucket tooth height (h), Manning coefficient of shoot surface (n), flip bucket radius (R), time (t), sedimentation basin width (B) and geometric standard deviation of non-uniform materials (σ). Using dimensional analysis and combining dimensionless parameters, the dimensionless densimetric Froude parameter (Frd) is achieved.In this study, after depiction of the longitudinal profile changes of the hole and mound scour due to falling jet, variations of the obtained dimensionless parameters were first investigated. Then, using statistical analysis, experimental relations to estimate the scour hole depth and downstream sediment mound height were presented. For this purpose, the effect of a tooth located at the end of a flip bucket on downstream bed topography changes was experimentally investigated considering different discharges, spillway gate opening percentages and tail water depths. After leveling bed sediment surface at the beginning of each experiment, discharge was adjusted using the electromagnetic flow meter and water depth was controlled using a spillway sluice gate. Besides, tail water depth was stabilized using a gate available at the end of the sedimentation basin and the falling jet was finally released to the basin. In order to determine experiment’s equilibrium time, several primary experiments were carried out considering different discharges in different time periods. By drawing equilibrium time curves, 360 min time duration equal to formation time of 88% of the total scour hole depth was considered as experimental time duration. Therefore, a total of 54 experiments were carried out considering the studied variables in this study. Water jet was released from 57 centimeters height of the bucket end level to the non-uniform bed sediments during 360 minutes experiments. Bed topography changes were measured at the end of each experiment using a dot sounder with 0.01 mm precision and depicted using Surfer V. 9.0. By calculating the changes of bed sediment volume, the influence of the slot on reduction of the scoured sediment volume can be evaluated in comparison to the normal condition. It was found that scour hole dimensions enlarge with discharge, but increase in tail water depth shows a descending procedure. In addition, in the case of slotted flip bucket in comparison to the normal one, by increasing gate opening by 33%, the hole volume increased by 125.64 %, and increasing gate opening by 66% and 99%, the hole volume decreased by 45.92 % and 22.85 %, respectively.

Cylindrical weirs- gates are one of the combined structures types which have advantages such as lower cost, simple design, easy construction and the high discharge coefficient. In current study, the cylindrical weir- gate location in perpendicular orientation to flow direction on discharge coefficient have been investigated experimentally. The experiments were conducted in a flume with the length of 7.5 m and width of 40 cm, using the cylindrical models were made up of plastic pipes with diameters of 50, 75, 110 and 125 mm. Experiments were conducted with different gate opening heights from 0 to 60 mm (reaching to the cylindrical gate by considering the available diameter and discharge). The results show that the maximum and minimum discharge coefficient has been observed respectively, in the cylindrical weir and cylindrical gate. Moreover, by converting the structure from cylindrical weir- gate to cylindrical gate, the curves depicted amount of Cds against the ratio of upstream flow depth to cylinder diameter (yup/D) and the ratio of difference between upstream and downstream flow depth to cylinder diameter ((yup-yd)/D) have reduced suddenly, which this progress was due to decreasing the amount of back water and remarkable decreasing in upstream depth. Furthermore, increasing in amount of cylindrical structure diameter leads to discharge coefficient amount decrease. The best correlated relations for quantifying the behavior of discharge coefficient Cd, were proposed.

Curved weirs in plan due to their special hydraulic conditions as well as long crest، have suitable capability in effective water surface regulation in irrigation canals and networks. Also، these weirs have high turbulence intensity in downstream and make better conditions for rivers، in environmental point of view. There are few studies regarding calculation of curved weirs’ discharge coefficient and their head discharge equation. In this study، using new optimization method of genetic programming، a dimensionless equation for discharge coefficient has been proposed based on two non-dimensional parameters of weir angel and ratio of water head to weir height. For training and testing of the proposed equation، experimental data of Kumar et al، have been used. Comparison of results obtained from this equation with the experimental data reveals high accuracy of the new equation of genetic programming. Mean absolute errors of the proposed equation for discharge coefficient have been calculated as 1. 36 and 1. 65 percent، for training and testing phases، respectively. This error for non-linear equation of Kumar et al، is nearly 9. 4 percent.

In Combined weir - gate structures، interaction of flow over weir and through gate brings up intense mixing and change bed shear stresses distribution. Hence، simulation of flow pattern in downstream of these structures is very complex. The object of this research is numerical modeling of combined flow over weirs and through gates by Flow3D software. Flow3D is a high accurate model in computational fluid dynamics for simulation of problem with complex geometry on wide limits of fluid flows in open channel hydraulic. By applying VOF method and RNG K-ε turbulent models، a series of simulation combined flow in weir - gate structure on rigid bed were performed and results were compared by some experimental data that carry out in this research. Results for the equation of Qup/Qin (equation 13) calculation error statistics software based on RMSE and R2 was evaluated and these values obtained 0. 0994 and 0. 992. Results of this research show that Flow3D with RNG K-ε turbulent model is appropriate to simulation of combined flow in weir - gate structure and estimation of free surface profile and discharge ratio passed over weir to under the gate.

The low efficiency and weak performance of Doroodzan irrigation and drainage network¡ and other irrigation and drainage networks in Iran¡ make researchers to evaluate and solve the problems. Water distribution and management of related structures are important research subjects. In Doroodzan irrigation network¡ radial gates and constant head orifices¡ control and deliver water to farms. Complexity of the radial gates hydraulic algorithms¡ and farmers interference in gates regulating¡ cause problems for water distribution. In the present study¡ the influence of weir elevation setting on offtaking discharge change was evaluated. The selected radial gate was closed about 20¡ 50¡ and 80% of the initial gate opening¡ and elevation of the external wasteway was raised about 7¡ 14¡ and 20 centimeter. Results showed that raising elevation of external wasteways to an elevation higher than internal wasteways¡ decreases the wastewater and the discharge changes in offtakes¡ and leads to easier management of the system.

Proportional weirs in which the discharge is linearly related to the head are known as linear proportional weirs. Because of unit power of their head, linear proportional weirs are more preferable than other traditional weirs in some situations. In this research, based on theoretical concepts different linear proportional weirs having inverted triangular, chimney and two inverted triangular sections were designed. Then, the weirs were constructed and their linear relationship was examined experimentally. 180 runs were conducted to compile the data in the discharge range between 1 and 8 l/s. The data proved the presence of linear relationships for all the examined weirs. The results are shown that relative error of 50%, 66% and 73% of experimental data for inverted triangular weir, chimney weir and two inverted triangle weir are between 1%±. Also, it is observed that the two inverted triangular weir performed better than that of other two weirs, that is, the two inverted triangular weir data had the minimum deviation from its proposed relationship.