flow

In this research, using the Oceanic Ninoy Index (ONI) during the statistical period of 1334 to 1401 water years, El Nino and La Niña periods have been identified and simultaneously with these periods, the natural monthly flow of the Karun Basin and the floods that occurred in the Karun River in The location of Karun Dam 3 has been obtained and compared. As a result of investigating the amount of flow and flood intensity in El Niño periods and comparing it with other situations, it was found that on average, in different seasons, the natural flow of Karun basin increases by 6 to 27% in El Niño periods. The highest increase is related to the fall season and the lowest increase is related to the summer season. Also, the most severe floods of the Karun river occurred simultaneously with the El Nino situation, and it seems that the intensity of the El Niño has a direct relationship with the intensity of the floods of this river.

In the production of reactive powdered concrete, fine-grained powder materials such as quartz sand, microsilica, and quartz powder are used as materials. This concrete has a high compressive strength compared to conventional concrete, which has attracted much attention in recent years. With this type of concrete, the weight of the structure can be significantly reduced, and its important features include high compressive strength, low permeability, durability and high abrasion resistance and high ductility that can absorb more energy during an earthquake. . In this research, we want to use limestone powder instead of a part of silica sand. For this purpose, after obtaining optimal mixing scheme based on the compressive strength and flow strength and diffusion diameter of the flow table, first replace the limestone powder with 0, 10, 20, 30 instead of silica sand, and then the powder Limestone has been used as a substitute-additive with different percentages and designs. The experiments performed on these samples included the psychological testing of the flow table and water absorption during treatment and compressive strength at the age of 7, 28 and 90 days. The results of the experiments show that by increasing the limestone powder up to 20% replacement with silica sand increases compressive strength, reduces very little in the psychological and also reduces water absorption during processing. In the production of reactive powdered concrete, fine-grained powder materials such as quartz sand, microsilica, and quartz powder are used as materials. This concrete has a high compressive strength compared to conventional concrete, which has attracted much attention in recent years. With this type of concrete, the weight of the structure can be significantly reduced, and its important features include high compressive strength, low permeability, durability and high abrasion resistance and high ductility that can absorb more energy during an earthquake. . In this research, we want to use limestone powder instead of a part of silica sand. For this purpose, after obtaining optimal mixing scheme based on the compressive strength and flow strength and diffusion diameter of the flow table, first replace the limestone powder with 0, 10, 20, 30 instead of silica sand, and then the powder Limestone has been used as a substitute-additive with different percentages and designs. The experiments performed on these samples included the psychological testing of the flow table and water absorption during treatment and compressive strength at the age of 7, 28 and 90 days. The results of the experiments show that by increasing the limestone powder up to 20% replacement with silica sand increases compressive strength, reduces very little in the psychological and also reduces water absorption during processing. In the production of reactive powdered concrete, fine-grained powder materials such as quartz sand, microsilica, and quartz powder are used as materials. This concrete has a high compressive strength compared to conventional concrete, which has attracted much attention in recent years. With this type of concrete, the weight of the structure can be significantly reduced, and its important features include high compressive strength, low permeability, durability and high abrasion resistance and high ductility that can absorb more energy during an earthquake. . In this research, we want to use limestone powder instead of a part of silica sand. For this purpose, after obtaining optimal mixing scheme based on the compressive strength and flow strength and diffusion diameter of the flow table, first replace the limestone powder with 0, 10, 20, 30 instead of silica sand, and then the powder Limestone has been used as a substitute-additive with different percentages and designs. The experiments performed on these samples included the psychological testing of the flow table and water absorption during treatment and compressive strength at the age of 7, 28 and 90 days. The results of the experiments show that by increasing the limestone powder up to 20% replacement with silica sand increases compressive strength, reduces very little in the psychological and also reduces water absorption during processing.

Increasing water elevation in dam reservoirs increases power plant working time and hydroelectric energy. If gated spillway is implemented, water elevation of reservoir can be increased without changing the dam height. Application of gate for spillways however increases discharge per unit width and the potential of cavitation attack. In the present work, using Flow3D software first the accuracy of the model was verified with experimental data of a stepped spillway. In the next step the spillway was gated keeping the flow discharge constant. To do this, the elevation of the ogee was increased and the chute width was narrowed. The main purpose of this study was to evaluate the pressure and cavitation potential in the gated step spillway. Studying flow condition in various gate opening showed that lower gate openings cause high negative pressures at the first step downstream of the gate. In the lowest opening of 10% -9.2 m pressure was observed at the first step tip. In addition, according to the results, tail of the gate pier caused flow separation and negative pressure was observed at the step at its downstream. The present work showed that numerical models are powerful instruments for optimization and design of hydraulic structures

Spillways and bottom outlets are the common hydraulic structures in dam engineering to convey excess water from the reservoir toward the downstream river. Economy and operation are the major factors affecting the type of spillway and its’ crest shape to avoid unfavorable hydraulic phenomena. An appropriate spillway crest results in increasing the discharge coefficient and distributing a uniform pressure inside the conveying conduits. One of the most common types of spillways in dam engineering is shaft spillways with morning glory inlet. Generation of swirling flow at the entrance of the shaft spillways and entraining air into the conduits is an unfavorable phenomenon. Air-entrainment into the system leads to different depressing effects on system operation including reduction of the discharge coefficient and can cause severe damages. To control the swirling flow phenomenon one way is the application of anti-vortex devices. Applying certain shape of inlets e.g. installing a Daisy (Marguerite)-shape inlet over the shaft entrance is another alternation to avoid the swirling flow effects thereby to increase the discharge coefficient. Marguerite-shape inlet has been used in different existing dam projects. Marguerite inlet is a unique inlet compared to other shapes of spillway crests for a constant head. This is in part due to spatially varied flow inside the marguerite inlet which makes it capable of passing greater discharge. Although different types of dam spillways have been the subject of different investigations, there is a lack of study on these types of spillways.
In this study, the effects of Daisy (Marguerite)-shape inlet on free-flow through shaft spillways have been investigated based on model experimentation. Dimensional analysis has been used to determine the effective dimensionless parameters. Experiments were conducted in a cylindrical model of 2 m diameter with two shafts of 10 and 12.5 cm diameters on the tank bottom. The tests have been performed based on a wide range of geometric and hydraulic parameters to study the effects of each dimensionless parameter on flow hydraulics. Finally, applying SPSS software and nonlinear regression analyses empirical correlations were obtained for estimating the discharge coefficient and the threshold depth of orifice flow over Daisy-shape inlets. To validate these correlations, the normalized root-mean-square error (NRMSE), the weighted quadratic deviation (WQD) and the coefficient of determination R2 were applied. Contrary to R2, both NRMSE and WQD must be small to have the best correlations.
Spillways and bottom outlets are the common hydraulic structures in dam engineering to convey excess water from the reservoir toward the downstream river. Economy and operation are the major factors affecting the type of spillway and its’ crest shape to avoid unfavorable hydraulic phenomena. An appropriate spillway crest results in increasing the discharge coefficient and distributing a uniform pressure inside the conveying conduits. One of the most common types of spillways in dam engineering is shaft spillways with morning glory inlet. Generation of swirling flow at the entrance of the shaft spillways and entraining air into the conduits is an unfavorable phenomenon. Air-entrainment into the system leads to different depressing effects on system operation including reduction of the discharge coefficient and can cause severe damages.

Structures such as side orifices, side weirs, and side sluice gates are known as flow diversion structures. Side orifices are flow diversion structures which have wide application in hydraulic and environmental Engineering. This flow diversion structure has been extensively used in irrigation and drainage networks, wastewater treatment plants, sedimentation tanks, etc. Therefore, Study of the characteristics and flow pattern such as flow velocity components and free surface adjacent to the side orifice is important. In this paper, the flow over a sharp-crested rectangular side orifice in an open channel was simulated by FLOW-3D software. RNG turbulence model was used to apply the Navier-Stokes equations and the VOF method was used to model the free surface profile changes. In the present study, at first, the results related to the side orifice discharge and flow patterns obtained from numerical simulation were compared with experimental data. In this study, some experimental data of Hussian et al (2011) were used for model verification. In this study, the discharges through the orifice resulted from the present numerical simulation and the experimental research, along with the relative errors are reported. All relative error quantities were about 8-9%, thus there was relatively good agreement between numerical and experimental results. Therefore, the numerical model can be employed as a powerful tool for studying flow through side orifices in open channels. Then the effects of height of the side orifice crest on the flow velocity components and free surface adjacent to the side orifice was investigated. The results indicated that the discharge ratio, ratio of the discharge through the side orifice to the inlet discharge of the main channel increases with decreasing heights of the side orifice crest. Maximum and minimum longitudinal velocity for all heights of the side orifice crest was occurred at the beginning and end of the side orifice, respectively. By decreasing the height of the side orifice crest, maximum and minimum longitudinal velocity increases and decreases, respectively. By decreasing the height of the side orifice crest, the longitudinal velocity in the vicinity of the side orifice is negative because of the reverse flow formed in this area. Examining the lateral velocity component variation showed that this component increased with decreasing height of the orifice crest. That is why the discharge through the side orifice increased with decreasing height of the orifice crest. At height 2.2 cm of the orifice crest, the flow direction is upward then in all cases vertical velocities in the orifice length are positive. In the other hand, at height 6.7 cm of the orifice crest, the flow direction is downward then in all cases vertical velocities in the orifice length are negative. Also, the absolute value of the vertical velocity increases with by decreasing the height of the side orifice crest because more flow is diverted to the side orifice with decreasing the height of the side orifice crest. Also, increasing height of the orifice crest caused significant changes in the free surface profiles especially in the vicinity of the side orifice.

Energy dissipation downstream of large dams is one of the most important concerns in the design procedure of dams. Flip buckets are employed whenever the velocity of flow at the downstream of the spillway is in excess of typically 20 m/s because of problems with stilling basins in terms of cavitation, abrasion and uplift. One of the most important issues in flip buckets is determining their optimal dimensions in order to increase the energy dissipation and reduce the maximum pressure on the surface of the flip bucket, simultaneously. Nowadays, the increasing computational power of computers to analyze complex problems, development of numerical modeling techniques and artificial intelligence models have caused them popular, in contrast with physical models which are often very time consuming and expensive. Hence, most of the researchers use these methods to analyze the complex engineering problems. In this research, by developing a new simulation-optimization methodology, the optimum dimensions of the flip bucket were determined based on the FLOW-3D model, artificial neural network (ANN) model and Genetic Algorithm (GA) models. The aim of determining the optimum dimensions is to calculate the radius of curvature and also the deflection angle of the flip bucket such that the maximum pressure on the surface of the bucket be minimum and the relative energy dissipation be maximum. Based on this methodology, in the first, the flip bucket of the Jareh dam was simulated for different radii and deflection angles using Flow-3D software. The calibration process was done in the basis of the experimental results which were obtained from the laboratory model. This laboratory model was built in the Water Research Institute of Tehran. Then, an artificial neural network (ANN) as a meta-model was trained using the maximum pressure on the surface of the bucket and the amount of energy dissipation after the impact of trajectory jet with the downstream channel bed. Then it was evaluated by the data that were not used during the training phase. The ability of this meta-model is to predict the values of the maximum pressure on the surface of the flip bucket and the amount of energy dissipation after the impact of trajectory jet with the downstream channel bed for different dimensions of flip bucket. Then by combining this neural network meta-model, with the genetic algorithm (GA) optimization model, the optimum dimensions of the mentioned flip bucket were determined. The optimum dimensions of flip bucket based on the mentioned objectives were found to be equal to the radius of 14 meters (0.28 m at physical model) and angle of 44.5 degrees. The results showed that despite the reduction of dimensions compared to the original size of flip bucket, the rate of energy dissipation has been increased (about 14% for the PMF flow).

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 ).

Rubber dams are hydraulic structures that are constructed on rivers which are cheaper than similar structures. In this research, rubber-dam modeling was performed by 3 different pressures inside the tube (1.5 to 3 KN/m2) and 3 discharges (1.5 to 5.5 lit/s) by Flow-3D software. A rubber dam, located on an open channel, was verified using an experimental model. The correlation coefficient resulted from fitting numerical model results and physical quantities, was 0.9357, which represents high accuracy of the numerical-model results. Maximum discharge coefficient was about 0.46 in discharge of 5.25 lit/s and pressure of 3 KN/m2. It was revealed that 100% increase in internal pressure of the tube leads to 5% increase in discharge coefficient. While, the same amount of discharge increase will lead to an increase of more than 25% in discharge coefficient. The H/Dh parameter was recognized as one of the effective factors on discharge coefficient. The modeling results showed that 31% increase of this parameter will increase discharge coefficient by 70%. Also, effective factors on flow velocity through the rubber dam were evaluated.

Diversion structures in side wall of open channel are to be used in order to divert flow from main channel. Side weirs, side orifices and side sluice gates are diversion structures which have wide application in dams, irrigation, drainage systems and combined sewer systems. Side weirs are one of the most important and applicable hydraulic structures for water controlling and directing systems that requires careful review and accurate designing due to their critical importance .In this paper, the flow over a sharp-crested rectangular side weir in open channel was simulated by FLOW-3D software. RNG turbulence model was used to apply the Navier-Stokes equations and the VOF method was used to model the free surface profile changes. In the present study, at first, results related to the distribution of the different components of velocity and angle of the outlet jet adjacent to the crest of the rectangular sharp crest side weir at various heights of the weir crest are validated with experimental data from Bagheri and Heidarpour (2012) research. Then the effects of upstream Froude number on flow pattern and free surface around the side weir were investigated. The results of this study indicated that with decreasing Froude number, maximum and minimum longitudinal velocity along the side weir increases and decreases, respectively. The maximum lateral velocity along the side weir increased with decreasing Froude number. That is why the discharge through the side weir increased with decreasing Froude number. The maximum vertical velocity along the side weir increased with decreasing the upstream Froude numbers because more flow is diverted to the side weir with decreasing the upstream Froude numbers. Distribution of the different components of velocity in the direction of flow height in the middle of the weir crest indicated that by reducing the upstream Froude number, longitudinal velocity distribution in the depth direction became more non uniform, especially near the weir crest. For different Froude numbers, lateral velocity would increased up to a certain elevation from the weir crest and then decreased toward the free surface. By increasing Froude number, the maximum lateral velocity occurs at greater heights above the side weir crest. The maximum vertical velocity for different Froude numbers occurred near the weir crest. Vertical velocity gradually decreased toward the free surface. By reducing the upstream Froude number, the vertical velocity near the free surface of flow is negative due to flow motion to downward. Free surface of the flow experienced extreme changes at the end of the side weir when upstream Froude number was increasing. By increasing the Froude number, the angle of inclination of the outlet jet along the side weir increases. Also by increasing the Froude number, the separation zone around the side weir in near the main channel bed, especially in the channel cross-section decreases.

One of the most efficient energy dissipatoion structures in open channels are block ramps; which has been considered and used most often recently because of the the simple performance. This kind of energy dissipatores can be assumed as a particular type of baffle block chutes, but with natural base materials and without cement structure. In laboratories, several physical models have been built and examined about their efficiencies. Regardless of the cost and time of tests and examinations, they have had the scale change problems. Today by using efficient computational fluid dynamics codes (CFD) fluid hydraulic behavior is more widely examined. This paper at first, reviews the classification of this structures from the point of fabrication and roughness from various point of views. Then deals with the formation of some types of flow regimes (volume flow rate) on them. In continue to the study, numerical simulation on one kind of this block ramps have performed and energy dissipation mechanism on various flow regimes on them have surveyed. For this reason, in this study Flow-3D software is utilized. In this research, incompressible fluid assumption, VOF method to calculate the free surface and LES turbulence model is used. The results showed the more energy dissipation with more turbulence and more turbulence with forming the recirculating flow and extending the distance of the reattachment point from the boulders. Consequently, energy dissipation is maximom for lower volume flow rate and higher slope of the ramp. Because in these two conditions, the flow involves with roughness of the ramp more and more; hence it gets easier for turbulent flow to happen. In other words, energy dissipation is also maximom for the non-submerged boulders. Flows in which boulders are submerged have different mechanism of energy dissipation. In these type of flows, energy dissipation is maximom for the wake-interface flow condition and isolated roughness flow condition respevtively. Therefore, in order to enhance the energy dissipation in flow over block ramps it is advised to reduce the effective cross section or reduce the submergence of scale roughness with holding the same effective cross section and the volume of fluid flowing over the structure. Because in these two conditions, the flow involves with roughness of the ramp more and more; hence it gets easier for turbulent flow to happen. In other words, energy dissipation is also maximom for the non-submerged boulders. Flows in which boulders are submerged have different mechanism of energy dissipation. In these type of flows, energy dissipation is maximom for the wake-interface flow condition and isolated roughness flow condition respevtively. Therefore, in order to enhance the energy dissipation in flow over block ramps it is advised to reduce the effective cross section or reduce the submergence of scale roughness with holding the same effective cross section and the volume of fluid flowing over the structure.

Multidimensional spillways are important hydraulic structures for regulating water level and flow in canals, rivers and reservoirs. The main hypothesis for the development is to increase the conveyance capacity through the spillway crest length at a given width. Finding an appropriate geometry has always been an important issue for designers in achieving maximum water productivity of hydraulic structures. In this study, several plans were simulated numerically considering effective length of spillway crest. Results showed that the highest reduction in the effective length of spillway crest occurs for plans with greater interference area at normal and lateral flows. Also, spillway model No. 5 was recommended as a sufficient plan in terms of flow capacity because of having just one interference area for normal and lateral flows and insignificant compaction during falling streams due to long lateral arms.

Due to hydraulic complexity in confluences, the study of different features of these locations such as sedimentation, erosion, and environmental considerations are of high interests to many researchers. Although many laboratory researches have been carried out regarding erosion and sedimentation in confluences, little researches have been done numerically. In this research the features and performance of FLOW-3D numerical model to simulate the flow, erosion, and sediment transport patterns in a junction of 2 canals with different flow rates and constant sediment flow, are investigated by comparing the results obtained from the numerical model with those obtained from a laboratory model. The widths of the canals of the physical model were 15 and 50 centimeters. The comparison between numerical and physical models shows an average of 6.3% error between maximum sediment depth in the junction of lateral and main canal between two models. Moreover, according to the measured results of erosion depth at the right bank of the main canal at the junction, the numerical model can estimate the erosion at the bank with the average of 26% error. Furthermore, the numerical model was able to predict the water surface profile of the flow in the junction with an average error of 1% when sediment was not injected.

Flow pattern in river bends is very complicated and fully three dimensional in nature with high turbulence intensity. This type of flow has a great influence on the river morphology by eroding the outer bank which results in deposits of sediment at the inner bank. Owing to the importance of the study of such flow، in this study flow in bend was simulated using FLOW-3D software. FLOW-3D utilizes a volume of fluid (VOF) method for free surface simulation. RNG turbulence model was used for closing the 3-D Reynolds-averaged Navier-Stokes equations. Experimental data from a laboratory study of flow in a rigid bed channel with a 90 degree bend were used to verify the results from the numerical model. The central radius of the bend and ratio of radius of the bend to width were 2. 4 m and 4، respectively. Numerical results showed good agreement with the experimental results. Then four ratios of radius to width of the bend: R/B=2، 3 4 and 5 were simulated to study the effect of ratio of radius to width on flow pattern. Based on the results of the longitudinal velocity component، at the start of the bend the cross-section maximum velocity occurred adjacent to the inner bank for all ratios of radius to width. Toward the end of the bend، in the sharpest bend (R/B=2)، maximum velocity occurred adjacent to the inner bank، but it shifted to the area close to the outer bank for other ratios of radius to width. The transverse slope of the free surface increases as the ratio of radius to width decreases.

Labyrinth spillways as appropriate hydraulic structure to pass PMF discharge have been considered. To replace existing spillways of reservoirs which in terms of capacity they are not hydraulically suitable، these types of spillways are recommended. In a certain width with similar head these spillways with nonlinear crest can pass greater discharges compare to spillways with frontal crest. The Labyrinth spillway is a type of hydraulic structure which can be used for the existing and new reservoirs. This structure is considered for hydraulic engineers as a good alternative to keep the water level of the reservoirs in an acceptable position when there is a limit on the maximum level of the water surface of the reservoir. The plan shape of the labyrinth spillway consists of broken lines in the form of triangular، trapezoidal، semi circular and rectangular with several repeating cycles. The main objective of using this type of spillway is to increase the flow capacity of the reservoir while keeping the crest and the water surface of the reservoirs in a reasonable level. The use of this type of reservoir goes back to the early 1920’s; however، the real studies and research in this field started form 1968. The majority of researches in this field are for those with triangular or trapezoidal in plan. The most advantages of using labyrinth spillway in the reservoirs and channels are as follows: 1- If the width of the spillway or channels cannot be chosen enough wide due to upstream or downstream site condition; 2- If the maximum level of the water in the reservoir during the flooding season is limited; 3- If it is desirable to provide larger water storage of the reservoir by making the crest level of the spillway higher without causing floodplain of upstream lands during high inflow to the reservoir; 4- If the capacity of the existing spillways are not large enough with respect to current standards of dams safety; 5- It is more economical due to the need of smaller discharge channel downstream of the spillway; and6- If the reservoir needs to have spillways with the gates to provide larger amount of water storage، in the case of labyrinth spillway the needs of the gates can be eliminated which is very advantageous both in terms of primary costs and maintenance costs. In this study by considering various angles of walls and lengths of nose different types of trapezoidal labyrinth spillways were designed. Applying Flow-3D software which is analytical software to solve equations of flow domain passed over spillway based on Eulerian viewpoint، numerical models were constructed. In order to model turbulence، the K-ε model in RNG state was used. Also to identify position of free surface profile، the VOF method was applied. To verify the results، experimental data of Tullis and Amanian (1995) was employed which the model results showed good agreement with the experimental data. Passing various discharges over the spillway variation of discharge coefficient was studied. It was showed with increase in length and angle of the spillway wall in flow direction the discharge coefficient would increase which is due to less interaction between the flow layers. This increase in small angles due to the reduction in over lapping layers is a considerable loss. At the end based on the obtained results a procedure to design a trapezoidal labyrinth spillway with choosing the angle of wall along the length of the nose was developed.