جستجوی مقالات مرتبط با کلیدواژه "discharge" در نشریات گروه "عمران"

Determining of discharge and the height of the run-off are considered to be the most basic hydrological elements of a basin in relation to the flooding of the basin, so that whenever the intensity of rainfall is greater than the capacity of water infiltration into the soil, the surface runoff flows over the basin and considering that The physiographic features of the basin are relatively stable, a direct relationship can be established between precipitation and runoff. Therefore, in this research, using physiographic and precipitation data, the amount of runoff in the central the Alborz sub-basins is investigated using the methods of Justin, Ikar, Ketain, England, Vermuel and Khozala. The results show that it is possible to determine the difference between Run-off by Justin's method and other mentioned methods gave a power relationship and a linear relationship between precipitation and runoff in different methods, that the estimation of runoff using Ikar's method has RMSE=0.0506, which is very close to Justin's method.

The ease of installing sluice gates and simplicity of their equations resulted in sluice gates as one of the most widely used hydraulic structures in regulating and controlling the water level. Several factors are discussed on the discharge coefficient of the sluice gate, including the effect of sill under the gate. The most important application of sill under sluice gate is to increase its discharge coefficient. Geometry and widths of sill is one of the important factors on discharge coefficient. also use of non-suppressed sills changes the flow pattern and the general equation of discharge coefficient. discharge coefficient of sluice gate with sill was studied by Jalil et al. (2016). In this study, the effect of sill under sluice gate was experimentally investigated on flow discharge coefficient. Results showed that the coefficient of discharge decreases with an increase of relative sill height to the head upstream. Rezavand (2018) investigated the effects of the hydraulic parameters on the flow discharge coefficient by Fluent software. Results showed that the sill under the gate has a positive effect on the flow discharge coefficient. The goal of this study is to investigate the geometry of sill with changes in its width on flow pattern and discharge coefficient in free-flow conditions. According to previous studies effect of sill width parameter with different geometric shapes on discharge coefficient and flow pattern has not been studied.

The experiments were performed in a hydraulic laboratory with flume dimensions of 5 m in length, 0.30 m in width, and 0.45 m in height. The walls are made from Plexiglass in order to provide good visibility. The inlet flow were measured by two rotameters with± 2% accuracy. Rotameters were installed at the outlet of the pump and measured with a point gage with an accuracy of 1 mm. a sluice gate with a 1 cm thickness is installed with the distance of 1.5 m away from the inlet of flow. The gate opening was fixed at 4 cm in all experiments. Sills including cylindrical, semicylindrical, pyramidal, and rectangular cubic were prepared in order to investigate the shape effect. All four sill shapes were prepared with widths of 5, 7.5, 10, 15, and 20 cm in order to study the effect of sill width under the gate. The height of all sills in this study was considered to be a fixed value of 3 cm. A total of 20 physical models were tested. In this study, flow discharge in the range of 475 to 700 liters per minute was applied to all models. A total of 200 experiments were performed in order to investigate the effect of sill shape and width on flow pattern and discharge coefficient in free conditions.

Results of sluice gate patterns with sill and without sill situations were investigated. The results of these experiments, similar to previous studies, show that a sluice gate with sill increases the discharge coefficient. The results showed that sills with different geometries affect flow under the gate. Also, using non-suppressed sills under the gate breaks the flow lines. As the downstream progress, v-shaped sections are formed. Investigation of flow patterns in cylindrical and semi-cylindrical and pyramidal sills showed pyramidal sill causes a significant uniformity flow lines compared to other geometric shapes due to its sloping side at downstream. while sill with rectangular cube geometry improves rotational flows at downstream of sill. The results of placing sill in different geometric shapes under sluice gate indicate that using semicy-lindrical sill compared to other shapes increases in discharge coefficient and the highest values of discharge coefficient after this sill are allocated to cylindrical, pyramidal and rectangular cubic sills, respectively. semicylindrical average discharge coefficient increased 19.1 percent compared with the gate without sill. According to the laboratory findings, it was observed that increased sill width with decreased gate opening increases the discharge coefficient. Placing a sill with a width of 20 cm in all geometric shapes increases the discharge coefficient by an average of 10% compared to a sill with a width of 5 cm.

The study of discharge coefficient in 20 physical models showed that the highest values of discharge coefficient after semicircular sill are allocated to circular, triangular, and square sills, respectively. This increase is expressed because the semicircular, circular, triangular, and square sills at the smallest width (b = 5 cm) increased discharge coefficient by 6.5, 5.6, 3.5, and 1.6% compared to non- sill state, respectively. Changing sill width from 5 to 20 cm showed that discharge coefficient of semi-cylindrical, cylindrical, pyramidal and rectangular cubic increased by an average of 19.1, 17.2, 14.7, and 12.1% compared to non- sill state.

The leakage is one of the main challenges in the operation of water distribution networks. In the present study, leakage location is detected using Feedforward Artificial Neural Networks (ANNs). For this purpose, two scenarios are considered for training the ANNs. In the first scenario, two simultaneous leakages with equal values, and in the second scenario, two simultaneous leakages but with unequal values are applied to every pair of network node. The training data are analyzed by EPANET2.0 hydraulic simulation software linked with the MATLAB programming language. In both scenarios, first, ANNs are trained using flow rates of total pipes number. Then, sensitivity analysis is performed by Hybrid ANNs for the flow rates of different percent of pipes number. The results of the proposed Hybrid ANNs indicate that in the first scenario, by having the flow rates of 10% of the total pipes, the locations of two simultaneous leakages are successfully determined. However, for the second scenario, while the difference between the two leakages is less than 80% of the maximum leakage (up to ratio value of 10 and 90 % leakages), by having the flow rates of 10% of the total pipes, the locations of the two leakages are still successfully determined. But for larger differences, only the location of the bigger leakage can be detected. Despite the complexities of the second scenario, the proposed ANNs could successfully detect the location of the bigger leakage.

Weirs are hydraulic structure commonly used for controlling flow characteristics and water level (Vischer, 1998). Also, in dams, weirs are responsible for the controlled release of flood flows from the dam reservoir to the downstream channels. One of the types of weir is piano key weir (PKW). Piano key weirs are also very cost-effective and cheap to maintain, increase reservoir storage capacity, and offer better flood control (Ortel, 2018). The main problem at the downstream of hydraulic structures, such as weir, is the scour and movement of bed materials. Scouring in the downstream of weirs is an important issue for weir stability and has been extensively researched. In this study, the geometry of scour holes in the downstream of piano key weirs was investigated by the use of experimental models. According to previous researches, trapezoidal piano key weirs (TPKW) are more efficient than rectangular piano key weir (RPKW) (Mehboudi, 2016). While there are limited studies on scour downstream of RPKWs, the scouring downstream of the trapezoidal piano key have not yet been researched according to the authors' knowledge(Jüstrich, 2016). So it is important to study their scour, and it is necessary to compare the performance of these two types of PKWs in terms of scouring issues. Due to the fact that the geometric shape of the weir affects the downstream scour condition, in this study the downstream scour of the piano key weir with trapezoidal geometric shape has been considered and the characteristics of the scour and its rate of was compared to a rectangular geometric shape. Accordingly, the impact of discharge and the tail water depth on the characteristics of the scour hole at the downstream of the rectangular and trapezoidal piano key weirs and the comparison of these changes in the two models have been considered. Measurements were made to predict the scour specifications of the rectangular and trapezoidal piano key weirs, including the maximum depth of the scour hole, the distance between maximum scour depth and weir foundation, and the length of the scour hole (Figure 2).

In this study, two experimental models of PKWs with rectangular and trapezoidal geometry were made and tested in a flume with a length of 6.0 m, a width of 1.0 m and a height of 0.6 m. 2.0 m length with an average thickness of 25 cm was formed from sandy material with median grain size d_50=7.8 m (Figure 3). Three hydraulic conditions in upstream and three different tail water depth considered in downstream and totally 18 experimental runs were conducted. A summary of the initial conditions, numbers, and codes of the experiments is given in Table 2. The range of changes in discharge in this research is between 19 to 33 liters per second. The reason for choosing this range for discharge is to examine the conditions of the scour profile in a wide range of flow rate changes. In addition, the dimensions of the channel and the pump used do not allow the discharge to exceed 33 liters per second.

Effect of discharge on the scour hole profile downstream of the rectangular and trapezoidal PKW models are shown in Figure (8). It can be seen that in all models, as discharge and upstream head increase, so do the hole depth and hole length and the distance of maximum scour depth from the weir toe. Previous studies have reported similar findings for linear and nonlinear weirs (Jüstrich, 2016). As shown in Figure (4),In this study, the arrangement of inlet and outlet keys of weirs was considered different from previous researches, so it was observed that the maximum depth of downstream scour occurs below the output keys, the reason for this is the external spill jets from the output keys, which cause the scour hole to fall into the downstream through vertex. Also, comparison the scour hole characteristics of downstream rectangular and trapezoidal piano key weirs in Figure (9) shows that the maximum scour hole depth downstream of the rectangular model is higher than the trapezoidal model. The higher score hole depth in the downstream of the rectangular model than the trapezoidal model in similar hydraulic conditions can be attributed to the fact that, for any given flow rate, upstream-downstream total head difference is greater in the rectangular weir comparison to the trapezoidal weir . As shown in Figure (11), For both rectangular and trapezoidal models, at a constant flow rate, the depth and length of the scour hole have decreased with the increase of tail water depth. It is due to a decrease in the height of the drop jet and increase in jet speed during impact to downstream flow. To determine the effect of the geometric shape of PKW and the tailwater depth, the scour characteristics in rectangular and trapezoidal models in the range of conducted experiments were examined and compared based on the configuration of Equation ∅_s/H=a〖F_rd〗^b (H/h)^c. Then, the nonlinear regression method was used to determine the coefficients a, b, and c and formulate a number of equations for predicting the maximum scour depth, its location, and the scour hole length for rectangular and trapezoidal PKWs. These equations are presented in Table (3) .

The measurement results of the cascade characteristics showed that with increasing the flow rate and decreasing the tail water depth, the geometric characteristics of the score hole increase in both models. Also, the depth of scour in the rectangular model is more than the trapezoidal model. in all discharges, on averagely, get decreases %7 the ratio of dimentionless maximum scour depth of trapezoidal piano key to the rectangular model. but this difference decreases with increasing flow and total head on the weir, so that when in F_rd>3.9 this difference becomes insignificant and there is not a significant difference in the shape of the hole for both models. Using the regression method, several equations with appropriate accuracy were formulated for predicting the maximum scour hole depth, its location, and the scour hole length downstream of the models.

Accurate river discharge estimation is one of the most important pillars in the management of surface water resources, especially for appropriate measures in flood situations, droughts, and drinking, agricultural and industrial applications. In this research, to estimate the discharge of the Zarrineh River, daily data and data of the Zarrineh River with a statistical period of 10 years at the site of the Sari Station of Qomish were used using the NeuroSolutions software. In this research, 60% of the data for training, 20% of data for validation and 20% for the rest were also used for testing. Various networks have been compared with multi-layered perceptron neural network (MLP), general predictor and radial base function. And the results indicate that the Multilevel Perceptron Neural Model (MLP) with the lowest mean square error was the best neural model. In this study, several networks with different transmission functions (TanhAxon, SigmoidAxon, LinearTanhAxon, and LinearSigmoidAxon) were compared. And the results indicate that the LinearTanhAxon transmission function with the lowest mean square error was the best transfer function. Also, networks with one and two hidden layers were compared and the results showed that the network with a hidden layer was better than the hidden two-layer network.

Gates in dams and irrigation canals are used for control of discharge or water surface regulation. To determine the discharge under a gate, discharge coefficient (Cd) should be determined. This study investigates the effect of sill shape under the vertical sluice gate on Cd. Both of sill shape and sill height are investigated. Investigated shapes comprise polyhedral and non-polyhedral sills. Results showed that circular sill is the most effective and triangular sill is also proper shape of polyhedral in increasing Cd. Circular sill increases Cd at least 23% up to maximum of 31%. In addition of shape, sill height is also important in determination of Cd. Using dimensionless parameters and regression analysis, an equation for prediction of Cd in free flow condition with and without sill is presented. The developed equation coincides with the published previous researches.Suggestions is for determination of Cd in submerged gate condition, and using FLOW3D or FLUENT software for more information about velocity and pressure distribution. Future experiments for producing more data set, can improve the accuracy of the developed equations.

Labyrinth weir is one of the approaches to increase the discharge capacity. An arced ‎configuration improves the orientation of the labyrinth weir cycles to the approach flow and ‎increases the weir crest length for a given width. In this study, the effects of the entrance flow ‎conditions on the hydraulic‏ ‏performance of the arced ‎labyrinth weirs is studied experimentally.‎‏ ‏The effects of the angle between the entrance channel walls (Θ′) on the discharge coefficient ‎and the efficiency are investigated for different values of the ‎headwater ratio (Ho/P), the ‎downstream sidewall angle (α), and the weir arc ‎angle (Θ).‎ Experiments were conducted in a recirculating flume‏ ‏which is 10 m long, 2 m wide, and 0.9 m ‎deep at Tarbiat Modares University. To simulate the reservoir conditions, a specific setup was ‎added to the flume, known as the reservoir simulator. The flume was launched from its two ends ‎by two pipelines. The inflow passes from underneath of the reservoir simulator and enters into it ‎through a semi-circular opening in its horizontal‏ ‏wall. After moving‏ ‏over the horizontal‏ ‏wall, the ‎flow comes up through the gap between the vertical wall. Finally, it flows on the platform and ‎moves towards the downstream channel. All the plates (including the platform and the simulator ‎walls) have a semicircular plan-view with a porosity equal to zero. The‏ ‏weirs were mounted on ‎the platform at the entrance of the downstream channel. Totally 132 experiments were ‎conducted to investigate the effects of the mentioned parameters on hydraulic performance of ‎arced labyrinth weirs.‎ Due to the nappe interference, the local submergence forms in the downstream of the ‎labyrinth ‎weirs. The size‎ of local submergence regions increase by increasing the ‎headwater ratio ‎and the arc angle. However, vice versa trend occurs with the downstream sidewall angle. In ‎addition, for low values of the arc angle, the lateral flow from the side cycles to their adjacent ‎cycles produces the surface turbulences. The results ‎indicate that the discharge coefficient ‎decreases by increasing the ‎headwater ratio and the downstream sidewall angle. For low values ‎of the ‎headwater ratio, the discharge coefficient increases when the arc angle increases. ‎However, a decreasing trend is observed in high head conditions. By increasing the ‎arc angle ‎and decreasing the downstream sidewall angle, the efficiency of a labyrinth weir can be ‎increased. However, the efficiency gains diminish by increasing the ‎headwater ratio.‎ The efficiency of a labyrinth weir can slightly be increased by projecting of the cycles into a ‎reservoir for low values of Ho/P, α, and Θ. However, in the wide range of the research domain, ‎the efficiency decreases‏ when ‏the angle between the entrance channel walls increases. ‎According to the results of this research, the efficiency of a labyrinth weir can be increased up ‎to 20% by channelizing abutments in high head conditions. However, the effect of Θ′ is ‎insignificant for higher values of Θ. In addition, as α decreases, the benefits and the losses of ‎decreasing Θ′ become more ‎severe at higher and lower values of Ho/P, respectively.‎

In the present study, the effect of sill on the discharge coefficient (Cd) of radial gates in a free flow condition has been investigated. Variable geometric parameters of these sills are length, upstream slope, downstream slope and sill height. In addition, the effect of sill location on Cd was investigated so that in case 1, with an open gate, the sill was located in front of the gate. In case 2, the sill is located under the gate and not in front of it. In total, 43 physical models of different shapes of sills and different sizes of sills were used. The results showed that when the radial gate is open and sills are in front of the gates (case 1), the sill operates as a barrier and reduces Cd. But in case 2, the semicircle shape has a better performance and increases Cd by about 30%. Also, the rectangular and trapezoidal sills always increase Cd. In these sills, increases in Cd depend on the sill length to its height (L/Z). Small values of L/Z increase the discharge coefficient up to 25%. Finally, for circular and semicircular sill shapes, two regression equations were presented which can be used by designers.

Weirs possess an essential role in dam safety and should spill floods with high return period. The designers can enhance the width of the weirs to increase the discharge capacity. But this has sometomes topography and economic limitations. Arced weirs can be considered as an alternative. A arced weir is a arcuate of a circle in plan-view that provides an increase in crest length for a given channel width that increas the flow capacity for the same head. Also when modification and capacity increase in existing spillways are necessary، this structure is recommended. In this paper، the hydraulic performance of arced weirs located in a reservoir has been studied experimentally. Firstly، dimensionless parameters affecting the performance of arced weirs is introduced using Buckingham π theorem. Then effect of arc angle (θ) and head water ratio (H0/P) on hydraulic performance of arced weirs was experimentally investigated and hydraulic performance of the tested arced weir geometries was compared with a linear configuration. For this purpose، Arches with different radius of curvature from linear to semi-circular configurations () and various head water ratio Were studied. To simulate reservoir conditions، a reservoir simulator was designed and built. Laboratory observations show that the converging of flow over a arced weir causes a locally bulge in the downstream of the weir. This phenomenon was named as flow mound. Results show that arc angle (θ) and head water ratio (H0/P) have a direct effect on the flow mound and an increase in each of them leads to mound height rise. The head-discharge relationship for arced weirs was determined by using a general form of the rectangular weir equation. Data from physical models were used to determine discharge and upstream head for the flat crested weirs installed in the reservoir. from discharge curves، it was found that with increasing angle of weir، that provide an increase in crest length for a given channel width، flow capacity increases for a given upstream head. Discharge coefficients as a function of H0/P for arced weirs are also presented and is compared with linear configuration. The results show that with increasing H0/P، discharge coefficient is declined for each tested configuration. Also with increasingθ، that leads to greater convergence of flow passing over the weirs، discharge coefficient decreases. Efficiency parameter is defined as the ratio of discharge of arced weir to that of liner weir with a same width. From efficiency curves it can be understood that the semi-circular weir can improve efficiency up to about 45%. However for all tested weirs، efficiency decreases with increasing H0/P and it gets close to 1. Finally، based on the results and limitations of this study، a methodology for the design of arced weirs located in the reservoir is presented. By using this method، the geometric parameters if an arced weir that is able to pass a certain flow rate for a given hydraulic head، will be determined.