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

Piano key weirs (PKW) is the newest type of long crest weirs, which achieve more crest length in the same width as congress weirs, and therefore, the capacity of the void is higher than that of the mounted piano key weirs, with the aim of increasing the amount of energy dissipation in them. It was noticed that the piano key weir oscilloscopes are used in the crest of reservoir dams and in irrigation and drainage networks. This has been implemented due to the importance of the issue of energy dissipation in these types of instruments. So far, many studies have been done on the discharge coefficient of the piano key weir, but no research has been done on the relative energy dissipation of the triangular Piano key weir.

This research is a continuation of previous research on PK weirs. Figure 1 shows the rotating flume environment, which experiments were performed in that laboratory at the Tarbiat Modares University of Tehran (Dimensions: 10 meters long, 2 meters wide, and 0.9 meters high). Experiments have been performed on a triangular weir with a zero slope (i.e., Tri-Base model) (Fig. 2 and 3) and 10 degrees in the flow direction (Fig. 2 and 4). In this article, PK weir with horizontal and sloped crest is called Tri-Base and Tri-B1 models. The weir characters used in the laboratory are provided in Table1. Eq (3).The upstream depth (ho = P+h) and downstream (h1) was measured with an accuracy of ± 0.1 mm at a distance of 4P for the upstream depth (Crookston, 2010) and 10P for the downstream of the overflow (Eslinger & Crookston, 2020).

For the ∆E/E0
curves, firstly, the relative energy dissipation curves for triangle PK weir with horizontal crest have been plotted (Fig 5) and compared with the present study and other researchers' results. The differences between results are because of the differences in geometric characteristics. Because the head and weir height changes for every discharge, Fig 6 has been plotted curves of (q - E1/E0).The trend of the relative energy dissipation curve of nonlinear weir may be according to a logarithmic curve (Lopes et al., 2011). Figure 5 shows the changes in energy consumption for the Tri-Base and Tri-B1 models and their comparison with the results of other researchers. According to Figure 5, the highest relative consumption of energy is for the Tri-Base model. In other words, at the same flow rate, the highest relative amount of energy dissipation is related to the weir model with a horizontal crest. It is also clear that the highest relative energy loss in all samples occurred at the lowest flow rates.As the flow rate increases, the relative dissipation of energy decreases in both models. The reason for this is that with the increase in flow rate and flow speed, the amount of flow friction is reduced, and as a result, the dissipation of the flow is reduced.With the increase of Froude Number, the acceleration increases, and the flow travels a longer path towards the separation, which causes the separation area to decrease and the Drag force to decrease. Because of the slope of the weir walls, the flow speed in the Tri-B1 model is higher than the Tri-Base model (the flow moves like a slide from the spillway to the downstream side), so the separation area in the Tri-B1 model is reduced, and the Drag force and consequently the relative depreciation The energy in the Tri-B1 model (about 24%) is lower than the Tri-Base model.Figure 6 shows the residual energy curve of the piano key weir in relation to the flow rate per unit of the overflow width. According to Figure 6, the E1/E2 ratio increases with the increase of flow per unit width. In other words, the relative residual energy in both models occurs at high flow rates. Also, in both models, at low flow rates, the increase in E1/E2 ratio is higher than at high flow rates. The reason for this is the local sinking upstream of the weir in high discharges; so that in high heads, the aeration on the weir is reduced.Finally, Fig 7 shows the comparison of measured and calculated values of triangular PK weir.

In the triangular piano key weir, by increasing the slope of the side walls (θ) from zero to 10 degrees in the flow direction, the relative dissipation of energy has decreased by 24%. Also, the highest dissipation of energy in the weir with a horizontal crest occurred in the lower heads, and this value decreases with the increase of the head.The highest amount of energy dissipation for Tri-Base and Tri-B1 models is 0.74 and 0.85, respectively, in this case. Finally, relationships (9) and (10) are proposed to calculate the relative energy consumption of the overflow of the piano key with horizontal and sloping crest, respectively.

In this study, the quantitative effects of the construction of Seymareh Dam in the Karst site of this structure on the fluctuations of groundwater level and discharge of springs have been investigated. According to 10-year measurements, it was found that there is a direct hydraulic relationship between the water surface of the dam reservoir and the water level of observation wells. The results revealed that a significant difference in the amount of water level of the North Edge wells compared to the South Edge wells, especially in the right abutment and the right abutment wells compared to the left abutment can be clearly seen, respectively, the evidence and confirmation of an Asmari core with Low permeability is along the axis of the anticline and also more efficiency of the sealing curtain on the right side is another reason for this difference. Changes in the total discharge of the total springs measured on both banks (right and left) have a similar trend to the changes in the discharge of the left bank springs, which is due to the more discharge of the left abutment springs. The results showed that with increasing the water level of the reservoir to 660 meters, the amount of discharge of springs in the region reached 1400 liters per second and with decreasing the level of reservoir water in the next year this amount decreased and again with increasing level to 704 meters, the amount of discharge to 1800 Liters per second has increased.

In this paper results of experiments on discharge coefficient of rectangular Piano key weirs are presented. Experiments were conducted using two Piano key weirs: one with sloped side walls crest and the other one with horizontal crest. Piano Key weirs with constant value of ratio of length to width were used. The results showed that water level upstream of weir with sloped side walls crest increased by about 11.02 percent. The discharge coefficient of weir with sloped side walls crest increased by about 4.8 percent. The efficiency of weir with sloped side wall crest is increases by about 7.3 percent. New equation for prediction of discharge coefficient of rectangular Piano key weir with sloped side walls crest and horizontal crest was obtained.

One of the critical consequences of climate change is prolonged droughts with floods. In these conditions, maintaining the maximum possible water level without wasting it and high discharge capacity in critical situations is essential to preserving the reservoir's health. The most suitable solution for sending excess water can be considered as creating a proper spillway. According to ICOLD, one-third of dam failures are due to weir disproportion. Unfortunately, due to the designers' lack of experience in using the nonlinear spillway, irreparable accidents sometimes happen. Therefore, choosing the proper spillway with the appropriate discharge have undeniable importance. This paper focuses on a new solution to improve the piano key weir capacity. By correcting the sidewalls of weirs, three goals were pursued simultaneously. In the first step, better performance than conventional PK weirs on the occasion of a flood. The second goal is to store the maximum water level upstream in non-critical situations and use only part of the weir.The ultimate goal is to make this method economical. This research is a continuation of previous research on PK weirs. Figure 4 shows the rotating flume environment, which experiments were performed in that laboratory at the Tarbiat Modares University of Tehran (Dimensions: 10 meters long, 2 meters wide, and 0.9 meters high)( Figure 4). Experiments have been performed on a triangular weir with a zero slope (i.e., Tri-Base model) (Fig. 1 and 2) and 10 degrees in the flow direction (Fig. 1 and 3). In this article, Pk weir with horizontal and sloped crest is called Tri-Base and Tri-B1 models. The weir characters used in the laboratory are provided in Table1. Eq (4) and (5). The dimensional analysis of the (Tri-B1) model, and the (Tri-Base) model, respectively. In the analysis of laboratory data, an effective length (wet length of walls) was defined for the weir. Then for this geometry, Eq. (6) and (7) were provided to calculate the discharge coefficient, which in addition to the new weir, is used in typical weir (i.e., The Tri-Base model) can also be used with great precision. Fig.10 shows the comparison of measured and calculated values of triangular pk weir.For the Head-Discharge curves, firstly, the discharge-head curves for triangle Pk weir with horizontal crest (Fig. 7) have been plotted and compared with the present study and other researchers' results. The differences between results are because of the differences in geometric characteristics shown in Table 2. Because the head and weir height changes for every discharge, Fig. 6 and have been plotted curves of (Q-P+Ht). Based on these figures, water height in triangle PK weir with a sloped crest (i.e., The Tri-B1 model) is higher than triangle pk weir with a horizontal crest (i.e., The Tri-Base model), but head height over the (Tri-B1) model is less than the (Tri_Base) model. On the other hand, for the (The Tri-Base) model, discharge coefficients have been plotted in Figure 8.This figure also compared the results of other researchers the results with this study. Fig. 9 also shows the discharge coefficient for the (Tri-B1) model. The discharge coefficient in the (Tri-B1) model has increased by an average of 3.8% than the (Tri-Base) model, with the maximum and average discharge coefficients shown in Table 3.Also, about the flowing blade, in the weir of a triangular Piano key weir with a horizontal crest, at 8 Cm 〖>H〗_t > 4 Cm, air penetrates under the blades of the flow, and the flow is vented. At higher values (12 Cm 〖>H〗_t > 8 Cm), the flow under the blade is connected to the open-air with increasing water head. In this case, have been seen fluctuations in the current blade. At higher values ( H_t>12 Cm), the flow completely covers the weir (immersion) and passes over the weir. In these conditions, the fluctuations of the flowing blade can be observed. According to Fig. 5 in Q=40lit/sec have seen an Air cavity on the weir body. Also, in analyze were seen, the weir of a piano key weir with a sloping crest (i.e., The Tri-B1 model) increased. But with the sinking whole of the weir, the discharge coefficient rate decreases. Also, in connection with the weir blade of the Pk weir with a sloped crest (The Tri-B1 model) in some discharges, all three types of flow blades can be seen on the sidewalls of the weir (i.e., sticky, compressed, and free baled. In conclusion, in Pk weir with slope crest, have been seen the level of water behind the weir increases while the head of water on the weir decrease. So this means that in drought seasons and when the level of water decreases in the reservoir, this spillway can increase the water level. Use this weir's high capacity in the critical season (especially during flood time). On the other hand, this spillway has a high capacity in all situation and increase the discharge coefficient.

A spillway is a very important structure usually used to provide the controlled release of water from a dam or sometimes levee downstream, typically into the riverbed of the dammed river itself. Spillways ensure that water does not destroy parts of the structures not designed to convey water. many Energy-dissipating structures (such as ., hydraulic jump stilling basins, roller buckets, ski jump buckets) are usually located at the end of spillways discharge channels in order to dissipate the extra energy which comes from the water . Specifically, flip buckets are mainly placed at the end of f high dams in order to dissipate the energy with high-velocity flows . having said that these structures ( Flip buckets) are used when velocity of the water is larger than about 15-20 m/s. Energy dissipation controlling has always been one of the most significant and vital matter and concern of hydraulic scientists and researchers especially in tall dams. one of the most common method to dissipate energy is to discharge flow away from hydraulic structures and downstream by using Flip bucket spill way .The sky-jump spillway is an economical and effective solution to return water to a river . many years ago in the past various models of flip bucket spillways , like simple, splitter, and deflector, and so on have been built,but information about the ways of increasing energy dissipation and controlling the bad effects of the extra energy of the water are still limited and more studies are needed .in order to increase the efficiency of this dissipater structure some wedge shape deflectors were designed to decrease the effect of this destructive energy on down stream.in this regard the effect of deflector installation position on energy dissipation was experimentally investigated. The main result indicate that the increase of linear distance of deflectors from the bucket remarkably result in an increase in energy dissipation and a decrease in jet length..

To investigate the effect of deflector installation position on energy dissipation and the length of the jet a new experimental study was conducted in the Hydraulic laboratory of Shahid Chamran university of Ahvaz.3 wedged-shape structures with Hight of 10 cm ,,length of 6 cm and angle of 47 degree were made .40 experiments were performed at 4 different linear distance from the edge of the bucket and one deflector-free experiment was carried out as a compression to other experiments. It is worth mentioning that all experiments including deflector-free one ,were performed at 8 dimensionless parameter Yc/H . At each experiment the linear distance from the edge of bucket was increased and the depth of tailwater was read .In the end relative energy dissipation was concluded by measuring the total energy in the upstream and downstream. in addition to the energy dissipation , Jet length ( for each experiment )was determined by using Get data software and the photos taken during the study .

In general Data analysis demonstrated that the waged-shape structures resulted in a remarkable increase in the amount of energy dissipation and a major decrease in jet length ,due to the increase of water and air mixture compare to the deflector - free experiments .Indeed deflectors divide the incoming jet to two small different jets ,therefore the combination of these two small jets leads to the increase in water and air mixture and consequently the increase of relative energy dissipation .Moreover it has been shown that the energy dissipation increased by increasing the linear distance from the bucket. Furthermore the experimental study on jet length indicated a remarkable decrease in the jet length by the increasing of the linear distance.in other words the different installation position of deflector increase the Hight of jet trajectory .it directly increases the contact surface of jet and air and leads to increase of energy dissipation and consequently decrease of jet length.

In general the increase of linear distance from the edge of bucket ( in flip bucket spillway ) resulted in the increase in energy dissipation and the decrease in jet length .Maximum observed relative energy dissipation was 65.87 which occurred in the Yc/H = 0.027 and Lx/L = 7.3 and minimum observed relative energy dissipation was 57.54 ,which occurred in the Yc/H = 0.061 and Lx/L = 4.3. furthermore maximum observed jet length was105 cm, which occurred in Yc/H = 0.061 and its minimum was 35 cm, which occurred in Yc/H = 0.027. therefor according to the results of the all experiments using deflector in different possessions as a new way of controlling and increasing energy dissipation is highly recommended .

In this study, using Modis images and wets pass model, the value of evapotranspiration for the northern Karun basin was estimated monthly from 2000 to 2014. The value of correlation coefficient for the obtained evaporations was R2 = 0.72. This model was calibrated and verified for different regions with different parameters. Data from 2000 to 2009 were used for calibration and data from 2010 to 2014 were used for validation of the model. The value calculated 0.54. In this study, with a review of climatic parameters of temperature, precipitation, evaporation during the period before the dam construction and after that, the effects on the microclimate of the area is investigated. Finally, to study the changes caused arising from the creation of a dam on the amount of evapotranspiration using the monthly images of Modis during the studied statistical period, the classification of images was done and the amount of changes were calculated. The results showed that the amount of evapotranspiration in the basin after the construction increased and its changes with distance from the dam in some months also has been increased.

Overflows are generally installed to drain excess water or floods that the volume of the tank can not store. In diversion dams, overflow is used to bypass or divert current in excess of system capacity. Demolition of many dams occurs due to incorrect design or insufficient overflow capacity. Proper spill design is more important in gravel earthen dams than in concrete dams. because the probability of destruction of earthen and gravel dams due to water passage is much higher than concrete dams. In the present study, a comprehensive review of the types of applied overflows based on effective dynamic and kinematic parameters was performed. Also, definitions and summaries of different types of free overflows were shot, siphon, stepped, congressional, lateral, tunnel, circular crown, peak, lotus or tulip. Then, the mechanism of vortex formation was introduced and an overflow appropriate to this phenomenon was introduced. The results of these cases showed that the application of lotus or tulip overflow in flood areas with high discharge has better performance.

The increasing need for clean water and energy resources for human societies has led them to optimize the old technologies with the best in research and studies to make the most of them. One of these inventions is dams, structures that are created on the rivers. In the past, the creation of dams was generally aimed at providing drinking water and irrigation of farms, but nowadays it is not only a source of water, but also electric energy. In many studies, dynamic analysis is used to assess the vulnerability and damage damages during an earthquake. Despite the precision of this method, there are many uncertainties in the analysis stages that make the study costly and prolonged. Therefore, using nonlinear static analysis method, researchers increased the speed of analysis and reduced costs. The purpose of this study is to investigate the seismic performance of concrete gravity dams using nonlinear static analysis (pushover analysis). For this purpose, load patterns used in the pushover analysis are applied in both directions upstream and downstream of the dam structure. Observations show that, apart from the rectangular load pattern, all load patterns used in this research can adequately correlate Detect the crack in the dam body correctly. The increasing need for clean water and energy resources for human societies has led them to optimize the old technologies with the best in research and studies to make the most of them. One of these inventions is dams, structures that are created on the rivers. In the past, the creation of dams was generally aimed at providing drinking water and irrigation of farms, but nowadays it is not only a source of water, but also electric energy. In many studies, dynamic analysis is used to assess the vulnerability and damage damages during an earthquake. Despite the precision of this method, there are many uncertainties in the analysis stages that make the study costly and prolonged. Therefore, using nonlinear static analysis method, researchers increased the speed of analysis and reduced costs. The purpose of this study is to investigate the seismic performance of concrete gravity dams using nonlinear static analysis (pushover analysis). For this purpose, load patterns used in the pushover analysis are applied in both directions upstream and downstream of the dam structure. Observations show that, apart from the rectangular load pattern, all load patterns used in this research can adequately correlate Detect the crack in the dam body correctly. The increasing need for clean water and energy resources for human societies has led them to optimize the old technologies with the best in research and studies to make the most of them. One of these inventions is dams, structures that are created on the rivers. In the past, the creation of dams was generally aimed at providing drinking water and irrigation of farms, but nowadays it is not only a source of water, but also electric energy. In many studies, dynamic analysis is used to assess the vulnerability and damage damages during an earthquake. Despite the precision of this method, there are many uncertainties in the analysis stages that make the study costly and prolonged. Therefore, using nonlinear static analysis method, researchers increased the speed of analysis and reduced costs. The purpose of this study is to investigate the seismic performance of concrete gravity dams using nonlinear static analysis (pushover analysis). For this purpose, load patterns used in the pushover analysis are applied in both directions upstream and downstream of the dam structure. Observations show that, apart from the rectangular load pattern, all load patterns used in this research can adequately correlate Detect the crack in the dam body correctly.

Selectivity the dams and Power plants is one of the most important issues in water resources management. The purpose of this paper was Selectivity the Khersan 1 dam and powerhouse by using one of the newest of the Multiple Attribute Decision Making (MADM) method in the name of Weighted Aggregated Sum Product Assessment (WASPAS) and its comparison with other MADM methods. In this case study that data required for making decision matrix is obtained in previous research, three alternatives: D axis- concrete arch, D axis- Pebble and F axis- concrete arch for selectivity by using WASPAS method with the help of the Excel 2010 software was analyzed. Calculated scores showed that D axis- concrete arch has achieved first priority (Q=0.9081), F axis- concrete arch has achieved second priority (Q=0.8487), finally D axis- Pebble has achieved third priority (Q=0.8202). Generally it can be said that SAW, AHP and WASPAS methods have led to the same result while TOPSIS had different result.

The aim of this research is establishing healthy, safety and environment management system in construction phase of a dam in Northern Zagros zone. Methods are based on three steps. The first step is risk factor identification. In this step, it has been studied which risks are caused by activities in operation phase in the three group of physical-chemical risk, biological risk and human risk. The second step is risk assessment. The risks are introduced in three criteria, severity, probability and vulnerability, and the environmental risk parameters have been scored by using expert opinion. The risks were prioritized by using Entropy method and TOPSIS Solver 2014 software. The results have shown that in the construction phase, reduction of aquatic life, destruction of vegetation and workers fall are of high risk. Moreover, in the third step the Healthy, Safety and Environment Managment System (HSE-MS) program is proposed in five steps. The first step is policy and objective. The second step is offering environment, health and safety plan. The third step is program implementation. The fourth step is monitoring and control on program, quality air, sewage and residue. The fifth step is reviewing the program implementation problem changing the monitoring plan.

Weirs have important roles in dam safety in which they should spill floods with high return period. Designers generally enhance width of the weirs to increase their discharge capacity. This procedure involves topography as well as economic limitations. Here, arced weirs can be considered as an alternative. In plan view, arced weir is part of a circle that increases the crest length for a given channel width. This increases the flow capacity at a similar heads. Such structures are also recommended for modification and increasing the capacity of the existing spillways. Discharge capacity of labyrinth weirs is a function of flow height, effective crest length, height of weir and shape of the crest. Discharge coefficient is also a function of height of flow, height of weir, weir thickness and crest shape. In this study, hydraulic characteristics of arced labyrinth spillways are numerically investigated. Here, the effect of crest shape on the discharge coefficient of the labyrinth spillway is included. In the first step, dimensionless parameters affecting the performance of arced weirs are introduced using Buckingham π theorem. To analyze this problem, a commercially available CFD code; Flow 3D by Flow Science; was selected. Flow 3D is known for its ability to accurately tracking free surface using Volume of Fluid (VOF) method. A similar method called Fractional Area to Volume Ratio (FAVOR) is used to define labyrinth within the model. Also, Reynolds averaged Navier Stokes (RANS) equations are solved using a finite volume method. Besides, The Renormalized Group Theory (RNG) model was implemented for turbulent simulations. The laboratory data of Crookston and Tullis (2012a) is used to validate the numerical model. These researchers conducted experiments on physical modeling of the labyrinth spillways at the Utah Water Research Laboratory at Utah State University. Comparison of numerical simulations with those of experimental results validates the ability of this software to simulate the complex flow over labyrinth spillways with an acceptable accuracy. In this study, result of 16 geometry models was used to develop a hydraulic design and analysis formulation for arced labyrinth weirs. Discharge coefficient data for Half-Round, Quarter-Round, Sharp-crest and Flat-crest arced labyrinth weirs are presented for 6̊ ≤ sidewall angles ≤ 24̊ and various head water ratio (0.1≤ H0/P ≤ 0.9). The study has shown that half round crest shape could increase the discharge coefficient about 22% compared to other crest shapes. Also, the results show that factors such as local submergence and nappe interference near an upstream apex has a negative impact on performance of arced labyrinth weirs. The local submergence area is directly related to the flow head, crest shape and sidewall angle. For high head conditions, the local submergence may decrease the efficiency of a labyrinth spillway. Efficiency parameter is defined as the ratio of discharge of arced weir to that of liner weir with the same width. From efficiency curves indicates that reduce of sidewall angle can improve efficiency. As a result, the highest efficiency related to arced labyrinth spillway with sidewall angle (α = 6̊ ).

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.

According to high potential of flood occurring in Iran, using flood control measures and introducing methods for reducing related damages, have been very essential to attention. Traditionally, the structural measures have been primary methods for flood control (Dam construction, flood control Dikes, and …). In this research a model for optimum sizing of flood control reservoirs, including dam height and spillway dimensions (length and height), and design return period, has been developed, based on economic benefit – cost analysis. In this model the benefit is reduction of flood damages in potential damage area, and cost is capital cost and OMR cost of system development. The model has been solved by LINGO12 package. The flood control system (dam) of Tange Sorkh River in Shiraz has been considered as case study. Based on model result, the annual net benefit, dam height., and spillway length have been achieved.