Iranian Hydraulic AssociationJournal of Hydraulics2345-423719120240320Laboratory investigation of the discharge coefficient of the rectangular piano key weir with a discontinuous sloping crestLaboratory investigation of the discharge coefficient of the rectangular piano key weir with a discontinuous sloping crest11217043410.30482/jhyd.2022.354595.1613FAHossein SohrabzadehKyoto universityMassoud GhodsianProfessor, Tarbiat Modarres UniversityJournal Article20220805Introduction ود <br />Spillways are simple and widely used hydraulic structures in water transfer and irrigation, and drainage systems. They are used in dams to pass excess water caused by floods and control the reservoir water level, as well as in irrigation and drainage canals to regulate the water level and measure the flow rate. Piano key weirs are the newest type of nonlinear weirs are piano key weir (PK weir), which this type of weir can increase the capacity of discharge coefficient 3-4 times to a linear spillway. However, the discharge coefficient of PK weirs decreases with increasing the head over the weir. <br />Methodology<br />This study aims to check the discontinuous wall over the crest of the piano key weir to improve the discharge coefficient of the piano key weir in the high heads. To achieve this goal, Two weirs with a ratio of W/B = 2/3 have been used (Figures 1 to 3). The desired weirs were installed and carried out in a rotating flume in the Tarbiat Modares University of Tehran (Figure 4). The range of testing was from Q = 55 lit/sec to Q = 180 lit/sec ; and with steps of 5 lit/sec. To conduct the tests, first, the tests were performed on the Rec-Base model, and then the tests were performed on the Rec-B1 model. The geometric features of these two models are presented in Table 1. <br />In order to extend the results of the prototype to the real sample, the dimensional analysis of the weir has been done. For this purpose, the effective parameters are shown in Eq. 2, and then, after performing the dimensional analysis techniques, it can be seen in the form of Eq. 3. By removing the constant values, the discharge coefficient will depend on the parameters of Eq. 4. <br />Results and Discussion<br />Figure 5 shows the Q-Ht curve of two Rec-Base and Rec-B1 models. According to this figure, the upstream head of the weir of the Rec-B1 model has increased by an average of 8.35% compared to the Rec-Base model. Also, regarding the behavior of the flowing blade, in the model (Re-Base) in the range of Ht<8 cm, air penetrates under the flow blades, and the flow becomes aerated. In the interval (Ht < 12 Cm < 8 Cm), with the increase of water head, the flow under the blade goes to the free air, and the blade takes an oscillating state. At higher values (Ht < 12 cm), The flow passes over the weir crest in the form of a thick blade. In this condition, fluctuations are observed on the flowing blade. Equation 5 has been used to calculate the discharge coefficient of the Rec-Base model. This issue is while Eq.12 has been used to calculate the water discharge coefficient of the Rec-B1 model. In this regard, QT is obtained from Eq. 10, and QE is the laboratory discharge. Figure 8 shows the discharge coefficient of the two models. According to this figure and the numbers in Table 2, the discharge coefficient has increased by 6.7% in the Rec-B1 model compared to the Rec-Base model. Figure 11 also shows a 7.22% increase in efficiency of the Rec-B1 model compared to the Rec-Base model. Also, coefficient C was calculated using equation 13 and its curve was drawn in figure 9. Figure 10 is also calculated according to Figure 14. Finally, Eq. 16 to estimate the water discharge coefficient has been presented. Also, the coefficients of this equation are presented in Table 3. Figure 12 shows the comparison between the estimated water discharge coefficient of equation 10 with the actual value of the discharge coefficient, which indicates the high accuracy of the presented equations. Table 4 indicates the equation proposed by other researchers to calculate the discharge coefficient of the PKW as well.<br />Conclusion<br />In conclusion, it can be mentioned that although the slope over part of the weir crest increases the upstream head of the piano key weir, however the efficiency of the weir increase by 7.33%. Also, the discharge coefficient in the Rec-B1 model increases by 6.7% compared to the Rec-Base model. Considering that in the Rec-Base model, with the increase of the head, interference of the flow increase, it is possible to reduce the decreasing rate of efficiency in higher discharge by modifying the weir crest.<br />Keywords<br />Spillway, rectangular piano key weir, weir crest, weir efficiencyIntroduction ود <br />Spillways are simple and widely used hydraulic structures in water transfer and irrigation, and drainage systems. They are used in dams to pass excess water caused by floods and control the reservoir water level, as well as in irrigation and drainage canals to regulate the water level and measure the flow rate. Piano key weirs are the newest type of nonlinear weirs are piano key weir (PK weir), which this type of weir can increase the capacity of discharge coefficient 3-4 times to a linear spillway. However, the discharge coefficient of PK weirs decreases with increasing the head over the weir. <br />Methodology<br />This study aims to check the discontinuous wall over the crest of the piano key weir to improve the discharge coefficient of the piano key weir in the high heads. To achieve this goal, Two weirs with a ratio of W/B = 2/3 have been used (Figures 1 to 3). The desired weirs were installed and carried out in a rotating flume in the Tarbiat Modares University of Tehran (Figure 4). The range of testing was from Q = 55 lit/sec to Q = 180 lit/sec ; and with steps of 5 lit/sec. To conduct the tests, first, the tests were performed on the Rec-Base model, and then the tests were performed on the Rec-B1 model. The geometric features of these two models are presented in Table 1. <br />In order to extend the results of the prototype to the real sample, the dimensional analysis of the weir has been done. For this purpose, the effective parameters are shown in Eq. 2, and then, after performing the dimensional analysis techniques, it can be seen in the form of Eq. 3. By removing the constant values, the discharge coefficient will depend on the parameters of Eq. 4. <br />Results and Discussion<br />Figure 5 shows the Q-Ht curve of two Rec-Base and Rec-B1 models. According to this figure, the upstream head of the weir of the Rec-B1 model has increased by an average of 8.35% compared to the Rec-Base model. Also, regarding the behavior of the flowing blade, in the model (Re-Base) in the range of Ht<8 cm, air penetrates under the flow blades, and the flow becomes aerated. In the interval (Ht < 12 Cm < 8 Cm), with the increase of water head, the flow under the blade goes to the free air, and the blade takes an oscillating state. At higher values (Ht < 12 cm), The flow passes over the weir crest in the form of a thick blade. In this condition, fluctuations are observed on the flowing blade. Equation 5 has been used to calculate the discharge coefficient of the Rec-Base model. This issue is while Eq.12 has been used to calculate the water discharge coefficient of the Rec-B1 model. In this regard, QT is obtained from Eq. 10, and QE is the laboratory discharge. Figure 8 shows the discharge coefficient of the two models. According to this figure and the numbers in Table 2, the discharge coefficient has increased by 6.7% in the Rec-B1 model compared to the Rec-Base model. Figure 11 also shows a 7.22% increase in efficiency of the Rec-B1 model compared to the Rec-Base model. Also, coefficient C was calculated using equation 13 and its curve was drawn in figure 9. Figure 10 is also calculated according to Figure 14. Finally, Eq. 16 to estimate the water discharge coefficient has been presented. Also, the coefficients of this equation are presented in Table 3. Figure 12 shows the comparison between the estimated water discharge coefficient of equation 10 with the actual value of the discharge coefficient, which indicates the high accuracy of the presented equations. Table 4 indicates the equation proposed by other researchers to calculate the discharge coefficient of the PKW as well.<br />Conclusion<br />In conclusion, it can be mentioned that although the slope over part of the weir crest increases the upstream head of the piano key weir, however the efficiency of the weir increase by 7.33%. Also, the discharge coefficient in the Rec-B1 model increases by 6.7% compared to the Rec-Base model. Considering that in the Rec-Base model, with the increase of the head, interference of the flow increase, it is possible to reduce the decreasing rate of efficiency in higher discharge by modifying the weir crest.<br />Keywords<br />Spillway, rectangular piano key weir, weir crest, weir efficiencyhttps://jhyd.iha.ir/article_170434_f4da5e27283dd04e99720417fcbd256e.pdfIranian Hydraulic AssociationJournal of Hydraulics2345-423719120240320Investigation of flow characteristics at the confluence of two compound channels (Numerical study)Investigation of flow characteristics at the confluence of two compound channels (Numerical study)132717724210.30482/jhyd.2023.376664.1627FASeyyed Mohammad Mahdi AlemiM.Sc. Student, Water Eng. and Hydraulic Structures, Department of Civil Engineering, Semnan University, Semnan, Iran.Hojat Karamiدانشگاه سمنان- دانشکده مهندسی عمران- گروه مهندسی آب و سازه های هیدرولیکیJournal Article20221220Introduction <br />The junction of open channels is one of the most important points that must be carefully studied. Because the phenomenon of the intersection of channels or rivers is very common, from nature to cities. On the other hand, the flow behavior at these points is very fast, complex and different due to the connection of two or more flows with different characteristics. Many and different studies have been done on this field, with different conditions and forms of the channel section. But the main goal of this article is to investigate the flow behavior at the junction of two compound channels. But according to the literature review and past researches, it can be concluded that the most of the researches included channels with a rectangular section, while most of the natural sections are closer to the compound section. Therefore, here the intersection of channels with a compound section is investigated.<br />Methodology <br />Until the last three decades, the study of fluid movement and the investigation of existing phenomena in this field, were only using experimental or analytical methods, with many assumptions to simplify it. But with the advance of computers, researchers were able to investigate more complex phenomena. One of these scientific fields that has made significant progress with the increase in computing power, is computational fluid dynamics or CFD, and one of its branches is hydraulic. Microscopic investigation of water behavior in natural streams is complex. Solving the existing theoretical models, in their complete form and with all the improvements, does not have the ability to correctly simulate its changes. But with the advance of computers, the science of CFD was able to successfully simulate and predict the behavior of water by using turbulence models. which There are different turbulence models with different applications that are used according to the type of problems. For calibration the model, the simulation’s results is compared with the experimental data. If the amount of error was small, it is concluded that the modeling has sufficient accuracy. So it is possible to continue the research and simulating other samples that have not been done in the laboratory, using Flow-3D software, and the effect of different parameters is investigating.<br />Results and Discussion <br />The profile of the water level in all cases of the intersection of two channels is such that the height of the water reaches a maximum in the middle of the intersection and then decreases to a minimum at a distance of about one meter from the intersection. After this point, the height of the water increases again to reach the equilibrium state. . However, among the effective parameters on the depth of water inside the channel, the effect of ratio of width of the channels, ratio of the flows and trapezoidal channel were investigated, with the assumption of constant angle of intersection of two channels (90 degrees).<br />Reducing the slope of the channels wall up to 10.5%, reducing the ratio of the main flow to the side channel up to 4.2% and reducing the ratio of the width of the main channel to the width of the side channel up to 33%, leads to a decrease in the minimum water depth compared to the base model (with a rectangular cross-section and a flow ratio of 0.25). Also with increasing the ratio of flow to maximum, the minimum depth increased by 7.5%.<br />The velocity and the turbulence energy were investigated for four specific simulations in order to get a better understanding of the intersection of two compound channels.<br />Conclusion <br />The main changes and characteristics of the intersection of two channels, are related to the characteristics of the sub-channel and are the result of the effect that the momentum of the sub-flow has on the main flow. U-velocity in the trapezoidal channel, decreased by 13.76% compared to the rectangular channel, and also the u-velocity in the minimum flow ratio was 1.33 times higher than the model with the maximum flow ratio. This indicates the importante effect of the sub-channel.Introduction <br />The junction of open channels is one of the most important points that must be carefully studied. Because the phenomenon of the intersection of channels or rivers is very common, from nature to cities. On the other hand, the flow behavior at these points is very fast, complex and different due to the connection of two or more flows with different characteristics. Many and different studies have been done on this field, with different conditions and forms of the channel section. But the main goal of this article is to investigate the flow behavior at the junction of two compound channels. But according to the literature review and past researches, it can be concluded that the most of the researches included channels with a rectangular section, while most of the natural sections are closer to the compound section. Therefore, here the intersection of channels with a compound section is investigated.<br />Methodology <br />Until the last three decades, the study of fluid movement and the investigation of existing phenomena in this field, were only using experimental or analytical methods, with many assumptions to simplify it. But with the advance of computers, researchers were able to investigate more complex phenomena. One of these scientific fields that has made significant progress with the increase in computing power, is computational fluid dynamics or CFD, and one of its branches is hydraulic. Microscopic investigation of water behavior in natural streams is complex. Solving the existing theoretical models, in their complete form and with all the improvements, does not have the ability to correctly simulate its changes. But with the advance of computers, the science of CFD was able to successfully simulate and predict the behavior of water by using turbulence models. which There are different turbulence models with different applications that are used according to the type of problems. For calibration the model, the simulation’s results is compared with the experimental data. If the amount of error was small, it is concluded that the modeling has sufficient accuracy. So it is possible to continue the research and simulating other samples that have not been done in the laboratory, using Flow-3D software, and the effect of different parameters is investigating.<br />Results and Discussion <br />The profile of the water level in all cases of the intersection of two channels is such that the height of the water reaches a maximum in the middle of the intersection and then decreases to a minimum at a distance of about one meter from the intersection. After this point, the height of the water increases again to reach the equilibrium state. . However, among the effective parameters on the depth of water inside the channel, the effect of ratio of width of the channels, ratio of the flows and trapezoidal channel were investigated, with the assumption of constant angle of intersection of two channels (90 degrees).<br />Reducing the slope of the channels wall up to 10.5%, reducing the ratio of the main flow to the side channel up to 4.2% and reducing the ratio of the width of the main channel to the width of the side channel up to 33%, leads to a decrease in the minimum water depth compared to the base model (with a rectangular cross-section and a flow ratio of 0.25). Also with increasing the ratio of flow to maximum, the minimum depth increased by 7.5%.<br />The velocity and the turbulence energy were investigated for four specific simulations in order to get a better understanding of the intersection of two compound channels.<br />Conclusion <br />The main changes and characteristics of the intersection of two channels, are related to the characteristics of the sub-channel and are the result of the effect that the momentum of the sub-flow has on the main flow. U-velocity in the trapezoidal channel, decreased by 13.76% compared to the rectangular channel, and also the u-velocity in the minimum flow ratio was 1.33 times higher than the model with the maximum flow ratio. This indicates the importante effect of the sub-channel.https://jhyd.iha.ir/article_177242_597d29aa6721cc879d55bd59502b41f7.pdfIranian Hydraulic AssociationJournal of Hydraulics2345-423719120240320Experimental and numerical evaluation of the effects of dam reservoir sediments on sediment transfer mechanism due to dam failureExperimental and numerical evaluation of the effects of dam reservoir sediments on sediment transfer mechanism due to dam failure294917541810.30482/jhyd.2023.384617.1631FAAmin MAldarDepartment of Civil engineering,, Science and Research Branch, Islamic Azad University Tehran, IranSeyed Abbas HosseiniDepartment of civil engineering, science and research branch, Islamic azad university, Tehran, Iran0000-0001-8858-3543Babak FazliZazd University, Babol BranchMeysam FazeliScience and Research Branch, Islamic azad University0000-0000-0000-0000Journal Article20230218Introduction <br />Dams are considered one of the most important infrastructure facilities of a country, which play a very important role in economic prosperity through storage, regulation of water, and also energy production. Due to the volume of water stored in the reservoir of these dams and sometimes their proximity to residential areas, the failure of dams can lead to a lot of human and financial losses, which can be prevented by having sufficient information and proper forecasts of dam failure. The flow resulting from the dam failure is turbulent, mainly a mixture of fluid and sediment particles. Therefore, after the dam's failure, sediment transport leads to significant morphological changes downstream. Based on this, the analysis and evaluation of the instantaneous failure of the dam have been one of the main challenges of the profession of engineers and activists in this field. By examining the research background, it is clear that the studies focused on fluid flow in non-erodible bed conditions, and a small part of numerical and laboratory research has been focused on the evaluation of changes in the morphology of the bed sediment layer. In addition, one of the effective parameters in the mechanism of sediment transfer and the pattern of morphological changes of the bed is the sediments of the dam reservoir, which has received less attention from researchers. Therefore, in this research, we have evaluated and experimental-numerically modeled the phenomenon of sediment transport due to the sudden failure of the dam, taking into account the sediment layer in the dam reservoir.<br /><br />Methodology <br />In this study, two variables (1- the type of sediment particles (fine sand and coarse sand) and 2- the thickness of the sediment layer in the reservoir and downstream of the dam) have been investigated as the main parameters in the evaluation of the sediment transport mechanism (changes in bed morphology). Based on this, scenarios have been defined for laboratory and numerical modeling. In this research, to evaluate the phenomenon of bed sediment transfer based on the phenomenon of instantaneous dam failure, four tests have been defined and implemented in the hydraulic laboratory flume of Babol University in different conditions. This flume is 10 meters long, 50 cm wide, and 50 cm high and is equipped with an ultrasonic level gauge and a digital pressure gauge. In these experiments, two parameters of the type of bed sediment materials (A, B) and also the thickness of the sediment layer downstream of the dam and the reservoir of the dam have been considered as modeling variables. Type A materials are gravel particles with an average diameter of 20 mm, and type B materials are sand particles with an average diameter of 3 mm.<br /><br />Results and Discussion <br />According to the research variables, four scenarios for laboratory modeling and six scenarios for numerical modeling of the phenomenon of sediment transfer based on instantaneous dam failure have been defined. The results of the numerical modeling showed that the numerical model of the research had acceptable accuracy in simulating the phenomenon of sediment transfer due to dam failure, so the modeling error for two-dimensional numerical models (the first four models based on Table 2) is respectively equal to 2.75%, 4.31%, 2.59%, 5.52% compared to laboratory tests.<br />The results showed that in the models of type B sediment materials, the amount of reduction in the thickness of the sediment layer is greater than in the models with type A sediment materials; in other words, the amount of reduction in the thickness of the sediment layer in type B materials is more than type B. The material was A. Therefore, the decrease in the diameter of the sediment particles has caused an increase in the thickness of the sediment layer (bed morphology) due to the failure of the instantaneous dam. In addition, by examining the results obtained from laboratory and numerical models, it was determined that the reservoir sediment layer of the dam is an effective parameter in the rate of sediment transfer and the occurrence of changes in the morphology of the bed based on the dam failure currents, in such a way that with the increase in the thickness of the sediment layer of the reservoir Compared to the downstream sediment layer of the dam, the changes in the thickness of the bed layer have increased by about 10%, as well as the rate of sediment transfer in these conditions.<br />By evaluating the results of dam failure modeling in three-dimensional space, it is clear that the thickness of the sediment layer in the 3D_DB1_NB1 model with type B materials has decreased more compared to the 3D_DB1_NA1 model with type A materials. In addition, according to the contour of the changes in the thickness of the bed layer, it is clear that the type of material of the sediment particles (diameter of the sediment particles) was an effective factor in evaluating the phenomenon of sediment transport in the 3D modeling space. In both 3D models, the thickness of the sediment layer in the area of the dam valve (failure area) has decreased and increased in the range of 1.8 to 2 meters and decreased from 2.2 to 3 meters.<br /><br />Conclusion <br />In this research, the main goal is to evaluate the mechanism of sediment transfer due to the sudden failure of the dam, focusing on the effect of the sediment layer in the dam reservoir, which has been implemented in the form of laboratory and numerical modeling. Also, the effect of three parameters, the type of sediment particles and the thickness of the sediment layer in the reservoir and downstream of the dam axis, has been studied.<br />Based on the results of this research and the evaluation and comparisons made between the numerical models and the laboratory model, it is clear that the numerical model created in both two-dimensional and three-dimensional spaces has an acceptable accuracy in simulating the phenomenon of sediment transfer due to dam failure.Introduction <br />Dams are considered one of the most important infrastructure facilities of a country, which play a very important role in economic prosperity through storage, regulation of water, and also energy production. Due to the volume of water stored in the reservoir of these dams and sometimes their proximity to residential areas, the failure of dams can lead to a lot of human and financial losses, which can be prevented by having sufficient information and proper forecasts of dam failure. The flow resulting from the dam failure is turbulent, mainly a mixture of fluid and sediment particles. Therefore, after the dam's failure, sediment transport leads to significant morphological changes downstream. Based on this, the analysis and evaluation of the instantaneous failure of the dam have been one of the main challenges of the profession of engineers and activists in this field. By examining the research background, it is clear that the studies focused on fluid flow in non-erodible bed conditions, and a small part of numerical and laboratory research has been focused on the evaluation of changes in the morphology of the bed sediment layer. In addition, one of the effective parameters in the mechanism of sediment transfer and the pattern of morphological changes of the bed is the sediments of the dam reservoir, which has received less attention from researchers. Therefore, in this research, we have evaluated and experimental-numerically modeled the phenomenon of sediment transport due to the sudden failure of the dam, taking into account the sediment layer in the dam reservoir.<br /><br />Methodology <br />In this study, two variables (1- the type of sediment particles (fine sand and coarse sand) and 2- the thickness of the sediment layer in the reservoir and downstream of the dam) have been investigated as the main parameters in the evaluation of the sediment transport mechanism (changes in bed morphology). Based on this, scenarios have been defined for laboratory and numerical modeling. In this research, to evaluate the phenomenon of bed sediment transfer based on the phenomenon of instantaneous dam failure, four tests have been defined and implemented in the hydraulic laboratory flume of Babol University in different conditions. This flume is 10 meters long, 50 cm wide, and 50 cm high and is equipped with an ultrasonic level gauge and a digital pressure gauge. In these experiments, two parameters of the type of bed sediment materials (A, B) and also the thickness of the sediment layer downstream of the dam and the reservoir of the dam have been considered as modeling variables. Type A materials are gravel particles with an average diameter of 20 mm, and type B materials are sand particles with an average diameter of 3 mm.<br /><br />Results and Discussion <br />According to the research variables, four scenarios for laboratory modeling and six scenarios for numerical modeling of the phenomenon of sediment transfer based on instantaneous dam failure have been defined. The results of the numerical modeling showed that the numerical model of the research had acceptable accuracy in simulating the phenomenon of sediment transfer due to dam failure, so the modeling error for two-dimensional numerical models (the first four models based on Table 2) is respectively equal to 2.75%, 4.31%, 2.59%, 5.52% compared to laboratory tests.<br />The results showed that in the models of type B sediment materials, the amount of reduction in the thickness of the sediment layer is greater than in the models with type A sediment materials; in other words, the amount of reduction in the thickness of the sediment layer in type B materials is more than type B. The material was A. Therefore, the decrease in the diameter of the sediment particles has caused an increase in the thickness of the sediment layer (bed morphology) due to the failure of the instantaneous dam. In addition, by examining the results obtained from laboratory and numerical models, it was determined that the reservoir sediment layer of the dam is an effective parameter in the rate of sediment transfer and the occurrence of changes in the morphology of the bed based on the dam failure currents, in such a way that with the increase in the thickness of the sediment layer of the reservoir Compared to the downstream sediment layer of the dam, the changes in the thickness of the bed layer have increased by about 10%, as well as the rate of sediment transfer in these conditions.<br />By evaluating the results of dam failure modeling in three-dimensional space, it is clear that the thickness of the sediment layer in the 3D_DB1_NB1 model with type B materials has decreased more compared to the 3D_DB1_NA1 model with type A materials. In addition, according to the contour of the changes in the thickness of the bed layer, it is clear that the type of material of the sediment particles (diameter of the sediment particles) was an effective factor in evaluating the phenomenon of sediment transport in the 3D modeling space. In both 3D models, the thickness of the sediment layer in the area of the dam valve (failure area) has decreased and increased in the range of 1.8 to 2 meters and decreased from 2.2 to 3 meters.<br /><br />Conclusion <br />In this research, the main goal is to evaluate the mechanism of sediment transfer due to the sudden failure of the dam, focusing on the effect of the sediment layer in the dam reservoir, which has been implemented in the form of laboratory and numerical modeling. Also, the effect of three parameters, the type of sediment particles and the thickness of the sediment layer in the reservoir and downstream of the dam axis, has been studied.<br />Based on the results of this research and the evaluation and comparisons made between the numerical models and the laboratory model, it is clear that the numerical model created in both two-dimensional and three-dimensional spaces has an acceptable accuracy in simulating the phenomenon of sediment transfer due to dam failure.https://jhyd.iha.ir/article_175418_f9c8da37f33334cd10c7e1125fa8df53.pdfIranian Hydraulic AssociationJournal of Hydraulics2345-423719120240320Determining the discharge coefficient in model of the triangular-rectangular combined weir and sliding gateDetermining the discharge coefficient in model of the triangular-rectangular combined weir and sliding gate516617609010.30482/jhyd.2023.395129.1642FAMohammad AsadiniyaM.Sc. Graduated of Water Structures, Department of Water Science and Engineering, University of BirjandHossein KhozeymehnezhadUniversity of birjand, Faculty member, Associate professorMohammad AkbariAssociate Professor of Department of Statistics, Faculty of Basic Sciences, University of BirjandJournal Article20230429Introduction: Measuring flow rate in water transmission channels has always been important. weirs and gates are more useful than other measuring tools and methods due to their low cost, ease of installation, ability to regulate and control the water level, as well as relatively simple and accurate relationships. Of course, each of these structures alone has weak points; For example, the settling of sediments behind the weir and the accumulation of floating materials behind the gate reduce their efficiency. In order to eliminate or reduce the weak points of weir and gate, the combination of these two structures in different ways and the research on hydraulics and the accuracy of the flow coefficient of the combined structure have been considered by researchers for some time. Therefore, in the current research, a triangular-rectangular combined weir structure and a sliding gate were built and its flow coefficient was investigated in different hydraulic conditions by a laboratory model in the hydraulic laboratory of Birjand University.<br /><br />Methodology: The experiments of this research in a laboratory flume with a length of 10 meters and a width of 0.3 meters in order to determine the discharge coefficient of the combined triangular-rectangular weir structure and the sliding gate, in two states of fixed opening of the gate and different flow rates and different opening of the gate and constant flow rates. And it was done in two slopes of 0.002 and 0.004. Finally, according to the existing relationship, the discharge coefficient of the structure was determined in different conditions. Dimensional analysis technique was used to generate dimensionless parameters and investigate the effect of these parameters on the discharge coefficient of the combined structure.<br /><br />Results and discussion: The results of the experiments were analyzed after checking the correctness and refinement of the data, and the discharge coefficient of the combined structure was analyzed according to the collected data and the geometrical and hydraulic parameters of the structure. The discharge coefficient of the combined structure was calculated in constant gate openings and different discharges and different gate openings and constant discharges. Also, in order to control some of the tests performed, the discharge coefficient of the combined structure was examined in two different slopes. In all these researches, the discharge coefficient of the combined structure was between 0.6 and 0.9, and the results became more uniforme with the increase of the upstream depth (y/D). The extraction of the gate of the combined structure downstream of the structure had an effect on the numerical value of the discharge coefficient of the combined structure.<br /><br />Conclusion: The test results showed that with the increase of y/D, the discharge coefficient first reaches its lowest value and then increases after the flow enters the rectangular weir and tends to 0.7. Also, by reducing the opening of the gate (H_g/D), the discharge coefficient tends to 0.7. Also, the intake of the gate of the combined structure increases the discharge coefficient of the structure. Slope changes have no effect in determining the discharge coefficient of the combined structure. The results of the current research with the results of other researchers who have worked in this field; It matches well.Introduction: Measuring flow rate in water transmission channels has always been important. weirs and gates are more useful than other measuring tools and methods due to their low cost, ease of installation, ability to regulate and control the water level, as well as relatively simple and accurate relationships. Of course, each of these structures alone has weak points; For example, the settling of sediments behind the weir and the accumulation of floating materials behind the gate reduce their efficiency. In order to eliminate or reduce the weak points of weir and gate, the combination of these two structures in different ways and the research on hydraulics and the accuracy of the flow coefficient of the combined structure have been considered by researchers for some time. Therefore, in the current research, a triangular-rectangular combined weir structure and a sliding gate were built and its flow coefficient was investigated in different hydraulic conditions by a laboratory model in the hydraulic laboratory of Birjand University.<br /><br />Methodology: The experiments of this research in a laboratory flume with a length of 10 meters and a width of 0.3 meters in order to determine the discharge coefficient of the combined triangular-rectangular weir structure and the sliding gate, in two states of fixed opening of the gate and different flow rates and different opening of the gate and constant flow rates. And it was done in two slopes of 0.002 and 0.004. Finally, according to the existing relationship, the discharge coefficient of the structure was determined in different conditions. Dimensional analysis technique was used to generate dimensionless parameters and investigate the effect of these parameters on the discharge coefficient of the combined structure.<br /><br />Results and discussion: The results of the experiments were analyzed after checking the correctness and refinement of the data, and the discharge coefficient of the combined structure was analyzed according to the collected data and the geometrical and hydraulic parameters of the structure. The discharge coefficient of the combined structure was calculated in constant gate openings and different discharges and different gate openings and constant discharges. Also, in order to control some of the tests performed, the discharge coefficient of the combined structure was examined in two different slopes. In all these researches, the discharge coefficient of the combined structure was between 0.6 and 0.9, and the results became more uniforme with the increase of the upstream depth (y/D). The extraction of the gate of the combined structure downstream of the structure had an effect on the numerical value of the discharge coefficient of the combined structure.<br /><br />Conclusion: The test results showed that with the increase of y/D, the discharge coefficient first reaches its lowest value and then increases after the flow enters the rectangular weir and tends to 0.7. Also, by reducing the opening of the gate (H_g/D), the discharge coefficient tends to 0.7. Also, the intake of the gate of the combined structure increases the discharge coefficient of the structure. Slope changes have no effect in determining the discharge coefficient of the combined structure. The results of the current research with the results of other researchers who have worked in this field; It matches well.https://jhyd.iha.ir/article_176090_50778e3c11895f5ce4824769898489b8.pdfIranian Hydraulic AssociationJournal of Hydraulics2345-423719120240320Experimental Evaluation of Performance of the New Design of Bed Protection Models (F-jacks) in Altering the Flow Pattern around Bridge PiersExperimental Evaluation of Performance of the New Design of Bed Protection Models (F-jacks) in Altering the Flow Pattern around Bridge Piers678617670010.30482/jhyd.2023.395247.1643FAZahra HeraviDepartment of Civil Engineering, Faculty of Engineering, University of Sistan and Baluchestan . Zahedan. Iran0000-0002-4032-8866Mehdi Azhdary MoghaddamUniversity of Sistan and Baluchestan0000-0002-7915-5229Kazem Esmailiwater and science engineering Dept.
Ferdowsi university of mashhadMohammad GivehchiAssistant ProfessorAbdolhamid Bahr PeymaDepartment of Civil Engineering, University of Sistan and BaluchestanJournal Article20230430Introduction <br />The various methods have been extensively studied by different researchers to reduce scouring around bridge piers, such as riprap, concrete blocks (CAU), collars, sacrificial piers, creating slot and roughness on the pier, and flow guide vanes, and their results generally relate to determining the size, location, and scope of installation and other geometric characteristics of the devices. Many countermeasures to prevent or reduce local scour around bridge piers, did not have the desired effective, and the concrete armor units (CAUs), which are made to protect shores from erosion caused by waves, have received very little attention in terms of bed armoring around the bridge piers.<br />Therefore, the aim of the present research is to experimentally investigate the hydrodynamics of flow around a new element designed to protect the bed around bridge piers from local scour. The F-jacks, a concrete armor unit (CAU), is introduced and its role on flow characteristics is evaluated for the first time in this study. This concrete element is a new design of the A-jacks concrete model, with one leg and five branches on top, and the angle between the branches surrounding the leg and the central branch is 30 degrees to ensure minimum contact between the legs of the element and the sediment surface. The selection of a 30-degree angle for the branches of the F-jacks element is due to its similarity to the diameter of the bridge pier, to provide complete coverage around the pier.<br />Methodology<br />The experiments of this research were performed in a 7-meter long, 50-centimeter wide, and 0.0001 slope flume with a rigid bed. A wooden cylinder with a diameter of D = 45mm and the same height as the flume was used as a model for a bridge pier and installed at a distance of 4.5 meters from the beginning of the flume (to develop the flow). The water depth (h) in the experiments was constant and equal to 15 centimeters, the flow rate (Q) was 0.021 m3/s, and the flow regime was fully turbulent and subcritical.<br />In order to understand the physics of flow in relation to three-dimensional velocity variations, a Nortek Acoustic Doppler velocimetry (ADV) with a frequency of 25 Hz and a sampling duration of 120 seconds was used. In order to evaluate the hydrodynamics of the flow around the protected pier with F-jacks units, three different placement patterns around the pier were considered: 1) a non-dense arrangement (P1), in which 24 F-jacks elements were placed next to each other around the pier, 2) a dense arrangement (P2), in which 22 F-jacks elements are interlocked around the pier, and 3) an SP arrangement, which refers to a situation where the single pier is placed in the central axis of the flume.<br />In addition to the measurement grid on the vertical XZ plane, a set of measurements was taken on the horizontal XY plane at Z/h=0.47 for each of the three selected patterns. To ensure the development of the flow in the test area, normalized mean velocity component profiles were shown to follow a similar trend for two 4 and 4.3 meter-long sections from the beginning of the flume, and the velocity data conforms to the logarithmic law of velocity distribution that confirms the validity of velocity data for developed flow conditions. Also, to verify the accuracy and sufficiency of measurements in the developed flow region under investigation, the power spectral density (PSD) of time series for all three velocity components shows that the slope of the power spectrum agrees well with the Kolmogorov -5/3 law in the inertial sub range.<br />Results and Discussion<br />Contour and vector plots of the time-average streamwise velocity component (u ̅) indicated that when the F-jacks elements were placed according to the P2 pattern around the pier, the flow pattern around the pier changes completely. Where, in the upstream of the pier, the average velocity significantly decreased from the water surface to the bottom, indicating the growth of the minimum and weakening of the downflow and horseshoe vortices. In the downstream of the pier, the high-velocity flow region at rear the pier disappeared, and the flow turbulence was significantly reduced, and the region of flow recirculation in the wake of the pier completely disappeared.<br />With the placement of F-jacks units around the pier, a strong upward vertical velocity (w ̅ ) is obvious around the pier compared to the single pier (SP pattern), which is stronger in the dense arrangement of the elements (P2 pattern). This factor refers to the positive effect of the presence of elements in reducing the growth of downflow (negative vertical velocity), reducing bed disturbances, and turbulence transfer away from the bed region in the wake area around the bridge pier.<br />The streamwise and vertical components of flow turbulence intensity (u_rms 〖,w〗_rms ) significantly decreased with the placement of F-jacks units around the pier according to the P2 pattern. Where, in the near-bed region around the pier, the turbulence intensity decreased by an average of about 93% compared to the SP pattern, indicating the high ability of F-jacks elements in controlling and reducing flow fluctuations and turbulence in this region and diverting flow fluctuations towards the water surface and away from the bed.<br />Comparison of Reynolds shear stress on XY plane at Z/h=0.47 for the three mentioned patterns revealed that -ρ(u^' w^' ) ̅ in the SP pattern is approximately 95% higher than P1 and P2 patterns, at the vicinity of the bridge pier. Furthermore, the magnitude of -ρ(u^' w^' ) ̅ has significantly decreased with the placement of F-jacks units as the P2 pattern around the pier.<br />Conclusion<br />The laboratory results presented in this paper provide a new understanding of flow behavior details around the bridge pier model with a new design of F-jacks armor units surrounding it on rigid bed conditions. The overall conclusion of this study showed that when F-jacks units are placed densely (P2 pattern) around the pier, the flow turbulence in this area is significantly reduced.Introduction <br />The various methods have been extensively studied by different researchers to reduce scouring around bridge piers, such as riprap, concrete blocks (CAU), collars, sacrificial piers, creating slot and roughness on the pier, and flow guide vanes, and their results generally relate to determining the size, location, and scope of installation and other geometric characteristics of the devices. Many countermeasures to prevent or reduce local scour around bridge piers, did not have the desired effective, and the concrete armor units (CAUs), which are made to protect shores from erosion caused by waves, have received very little attention in terms of bed armoring around the bridge piers.<br />Therefore, the aim of the present research is to experimentally investigate the hydrodynamics of flow around a new element designed to protect the bed around bridge piers from local scour. The F-jacks, a concrete armor unit (CAU), is introduced and its role on flow characteristics is evaluated for the first time in this study. This concrete element is a new design of the A-jacks concrete model, with one leg and five branches on top, and the angle between the branches surrounding the leg and the central branch is 30 degrees to ensure minimum contact between the legs of the element and the sediment surface. The selection of a 30-degree angle for the branches of the F-jacks element is due to its similarity to the diameter of the bridge pier, to provide complete coverage around the pier.<br />Methodology<br />The experiments of this research were performed in a 7-meter long, 50-centimeter wide, and 0.0001 slope flume with a rigid bed. A wooden cylinder with a diameter of D = 45mm and the same height as the flume was used as a model for a bridge pier and installed at a distance of 4.5 meters from the beginning of the flume (to develop the flow). The water depth (h) in the experiments was constant and equal to 15 centimeters, the flow rate (Q) was 0.021 m3/s, and the flow regime was fully turbulent and subcritical.<br />In order to understand the physics of flow in relation to three-dimensional velocity variations, a Nortek Acoustic Doppler velocimetry (ADV) with a frequency of 25 Hz and a sampling duration of 120 seconds was used. In order to evaluate the hydrodynamics of the flow around the protected pier with F-jacks units, three different placement patterns around the pier were considered: 1) a non-dense arrangement (P1), in which 24 F-jacks elements were placed next to each other around the pier, 2) a dense arrangement (P2), in which 22 F-jacks elements are interlocked around the pier, and 3) an SP arrangement, which refers to a situation where the single pier is placed in the central axis of the flume.<br />In addition to the measurement grid on the vertical XZ plane, a set of measurements was taken on the horizontal XY plane at Z/h=0.47 for each of the three selected patterns. To ensure the development of the flow in the test area, normalized mean velocity component profiles were shown to follow a similar trend for two 4 and 4.3 meter-long sections from the beginning of the flume, and the velocity data conforms to the logarithmic law of velocity distribution that confirms the validity of velocity data for developed flow conditions. Also, to verify the accuracy and sufficiency of measurements in the developed flow region under investigation, the power spectral density (PSD) of time series for all three velocity components shows that the slope of the power spectrum agrees well with the Kolmogorov -5/3 law in the inertial sub range.<br />Results and Discussion<br />Contour and vector plots of the time-average streamwise velocity component (u ̅) indicated that when the F-jacks elements were placed according to the P2 pattern around the pier, the flow pattern around the pier changes completely. Where, in the upstream of the pier, the average velocity significantly decreased from the water surface to the bottom, indicating the growth of the minimum and weakening of the downflow and horseshoe vortices. In the downstream of the pier, the high-velocity flow region at rear the pier disappeared, and the flow turbulence was significantly reduced, and the region of flow recirculation in the wake of the pier completely disappeared.<br />With the placement of F-jacks units around the pier, a strong upward vertical velocity (w ̅ ) is obvious around the pier compared to the single pier (SP pattern), which is stronger in the dense arrangement of the elements (P2 pattern). This factor refers to the positive effect of the presence of elements in reducing the growth of downflow (negative vertical velocity), reducing bed disturbances, and turbulence transfer away from the bed region in the wake area around the bridge pier.<br />The streamwise and vertical components of flow turbulence intensity (u_rms 〖,w〗_rms ) significantly decreased with the placement of F-jacks units around the pier according to the P2 pattern. Where, in the near-bed region around the pier, the turbulence intensity decreased by an average of about 93% compared to the SP pattern, indicating the high ability of F-jacks elements in controlling and reducing flow fluctuations and turbulence in this region and diverting flow fluctuations towards the water surface and away from the bed.<br />Comparison of Reynolds shear stress on XY plane at Z/h=0.47 for the three mentioned patterns revealed that -ρ(u^' w^' ) ̅ in the SP pattern is approximately 95% higher than P1 and P2 patterns, at the vicinity of the bridge pier. Furthermore, the magnitude of -ρ(u^' w^' ) ̅ has significantly decreased with the placement of F-jacks units as the P2 pattern around the pier.<br />Conclusion<br />The laboratory results presented in this paper provide a new understanding of flow behavior details around the bridge pier model with a new design of F-jacks armor units surrounding it on rigid bed conditions. The overall conclusion of this study showed that when F-jacks units are placed densely (P2 pattern) around the pier, the flow turbulence in this area is significantly reduced.https://jhyd.iha.ir/article_176700_c8d7f79d5154573d70e6d49814770177.pdfIranian Hydraulic AssociationJournal of Hydraulics2345-423719120240320The Numerical Investigation of hydraulic condition on flip bucket spillways and effect of inlet flow and shape on itThe Numerical Investigation of hydraulic condition on flip bucket spillways and effect of inlet flow and shape on it879917670110.30482/jhyd.2023.396298.1645FAHessam VatandoustDepartment of Civil Engineering, Parand &amp; RobatKarim Branch, Islamic Azad UniversityAli Mahdi AbhariCivil Aviation TechnologyJournal Article20230509Introduction<br />Since beginning of the dam construction industry, one of the challenges that engineers have always been involved with, is how to reduce the enormous energy of water when it overflows from dams for which, many plans and ideas have been presented so far. One of these ideas is to utilize the energy dissipater structures among which, the flip buckets are well-known. Since the flip bucket is one of the most important components of a dam, whose destruction disrupts the normal performance of the dam, the engineers have always tried to enhance the efficiency of this component by investigating into the hydraulic conditions such as pressure, depth and velocity. Accordingly, it is of paramount significance to comprehensively study the hydraulic performance and condition of the flip buckets<br />Methodology<br />In this study, behavior of the fluid in the flip bucket of a dam has been modeled using Flow-3D software. The obtained results in Froude number, were compared with the data derived from an existing physical model. After determining the error percentage and selecting the turbulence model etc., using the continuity and motion equations in the fluid dynamics and finite volume method, a model was built and through a trial-and-error process, Froude numbers ranging from, 2 to 7 were chosen. The results pertained to the velocity, static pressure and depth were captured and compared with geometric characteristics of the bucket and incoming flow condition. To efficiently employ the results, the produced graphs were normalized using a similitude analysis. The comparisons have been made with the non-dimensional ratios of Froude number and x/r (x: distance from the bucket and r: bucket radius) in the middle as well as right and left sides<br />Results and Discussion<br />In order to choose the turbulence model (K-ε, K-ω and RNG turbulence models were used to compare the results of various models according to previous studies), after analyzing and optimizing the computational error between the numerical and the physical models, the k-ε model with the minimum rate of error was selected as the best practice. It needs to be noted that the error rate of pressure, velocity and depth are 1.52%, 1.5% and 1.58%, respectively. The results indicated that the velocity changes along the length of the bucket, generally have a slight increasing trend and reach their maximum value at the end of the bucket. In addition, velocity changes have an inverse trend as the Froude number increase. Moreover, it was observed that the depth changes are almost constant along length of the bucket and reach their minimum value at the end and decrease with the depth as the Froude number increases. Pressure changes also have a decreasing trend along the length of the bucket and also, decrease with increase in the Froude number. The situation of the above parameters in the sides is generally similar to the middle axis, but with a greater intensity<br />Conclusion<br />It can be generally stated that the most vulnerable zone of the flip bucket is where 0.1<x/r<0.3 (i.e., the region where flow runs backs to the top) in great Froude numbers. This zone is the critical area of the bucket structure due to the decrease in pressure, both in terms of the possibility of cavitations and increasing velocities. Furthermore, it was found that rate of vulnerability in the sides is greater than the middle. Moreover, range of the pre-final Froude numbers of the flow passing through to the bucket, is the turning point of the flow hydraulic condition that needs to be considered while designing this structure.Introduction<br />Since beginning of the dam construction industry, one of the challenges that engineers have always been involved with, is how to reduce the enormous energy of water when it overflows from dams for which, many plans and ideas have been presented so far. One of these ideas is to utilize the energy dissipater structures among which, the flip buckets are well-known. Since the flip bucket is one of the most important components of a dam, whose destruction disrupts the normal performance of the dam, the engineers have always tried to enhance the efficiency of this component by investigating into the hydraulic conditions such as pressure, depth and velocity. Accordingly, it is of paramount significance to comprehensively study the hydraulic performance and condition of the flip buckets<br />Methodology<br />In this study, behavior of the fluid in the flip bucket of a dam has been modeled using Flow-3D software. The obtained results in Froude number, were compared with the data derived from an existing physical model. After determining the error percentage and selecting the turbulence model etc., using the continuity and motion equations in the fluid dynamics and finite volume method, a model was built and through a trial-and-error process, Froude numbers ranging from, 2 to 7 were chosen. The results pertained to the velocity, static pressure and depth were captured and compared with geometric characteristics of the bucket and incoming flow condition. To efficiently employ the results, the produced graphs were normalized using a similitude analysis. The comparisons have been made with the non-dimensional ratios of Froude number and x/r (x: distance from the bucket and r: bucket radius) in the middle as well as right and left sides<br />Results and Discussion<br />In order to choose the turbulence model (K-ε, K-ω and RNG turbulence models were used to compare the results of various models according to previous studies), after analyzing and optimizing the computational error between the numerical and the physical models, the k-ε model with the minimum rate of error was selected as the best practice. It needs to be noted that the error rate of pressure, velocity and depth are 1.52%, 1.5% and 1.58%, respectively. The results indicated that the velocity changes along the length of the bucket, generally have a slight increasing trend and reach their maximum value at the end of the bucket. In addition, velocity changes have an inverse trend as the Froude number increase. Moreover, it was observed that the depth changes are almost constant along length of the bucket and reach their minimum value at the end and decrease with the depth as the Froude number increases. Pressure changes also have a decreasing trend along the length of the bucket and also, decrease with increase in the Froude number. The situation of the above parameters in the sides is generally similar to the middle axis, but with a greater intensity<br />Conclusion<br />It can be generally stated that the most vulnerable zone of the flip bucket is where 0.1<x/r<0.3 (i.e., the region where flow runs backs to the top) in great Froude numbers. This zone is the critical area of the bucket structure due to the decrease in pressure, both in terms of the possibility of cavitations and increasing velocities. Furthermore, it was found that rate of vulnerability in the sides is greater than the middle. Moreover, range of the pre-final Froude numbers of the flow passing through to the bucket, is the turning point of the flow hydraulic condition that needs to be considered while designing this structure.https://jhyd.iha.ir/article_176701_6c0083b021c2c2eb5420d4243422146c.pdfIranian Hydraulic AssociationJournal of Hydraulics2345-423719120240320The Performance of Differential Evolution Algorithm for Leak Detection in Water Distribution Networks Considering The Uncertainty of Nodal DemandsThe Performance of Differential Evolution Algorithm for Leak Detection in Water Distribution Networks Considering The Uncertainty of Nodal Demands10111817670210.30482/jhyd.2023.396745.1646FAShahrzad Madani EsfahaniFaculty of Civil. Water and Environmental engineering, Shahid Beheshti UniversityJafar YazdiFaculty of Civil. Water and Environmental engineering, Shahid Beheshti University0000-0002-0867-9658Journal Article20230515Water supply networks are one of the most important urban infrastructures for supplying water. Considering that currently water wastage is a global concern and on the other hand the demand for water is increasing, this issue has made it necessary to manage the demand and modify the consumption pattern. One of the important components of non-revenue water is leakage in the water supply network, and leak detection is one of the necessary measures to reduce non-revenue water and manage consumption. In this research, an optimization formulation has been developed for the purpose of leak detection in water networks assuming the lack of information on the number of leaks and pressure measurement data, and the search problem has been solved with the differential evolution algorithm. The performance of the developed model has been investigated by defining different scenarios in terms of location, amount and number of leaks. First, the location scenarios were examined in terms of the number and amount of leaks, including one, ten, and twenty leaks at the same time, and then the developed model was implemented for location scenarios with an unknown number of leaks and the uncertainty of nodal needs. The results showed that the success of the model in the case of the certainty of the input data and the existence of a node is 100%, and by considering the hourly changes in the nodal demand and increasing the number of leaks up to ten and twenty leak nodes, the success rate of the model in finding the exact leak points is 95% and 94.5% has been obtained. In the scenarios where the number of leaks was considered unknown, the success of the model to find the number of leaks is 94%. The success of the model in the case of uncertainty of nodal requirements with the number of known leaks reaches 91% with the increase of leaks and 86% with the number of unknown leaks.Water supply networks are one of the most important urban infrastructures for supplying water. Considering that currently water wastage is a global concern and on the other hand the demand for water is increasing, this issue has made it necessary to manage the demand and modify the consumption pattern. One of the important components of non-revenue water is leakage in the water supply network, and leak detection is one of the necessary measures to reduce non-revenue water and manage consumption. In this research, an optimization formulation has been developed for the purpose of leak detection in water networks assuming the lack of information on the number of leaks and pressure measurement data, and the search problem has been solved with the differential evolution algorithm. The performance of the developed model has been investigated by defining different scenarios in terms of location, amount and number of leaks. First, the location scenarios were examined in terms of the number and amount of leaks, including one, ten, and twenty leaks at the same time, and then the developed model was implemented for location scenarios with an unknown number of leaks and the uncertainty of nodal needs. The results showed that the success of the model in the case of the certainty of the input data and the existence of a node is 100%, and by considering the hourly changes in the nodal demand and increasing the number of leaks up to ten and twenty leak nodes, the success rate of the model in finding the exact leak points is 95% and 94.5% has been obtained. In the scenarios where the number of leaks was considered unknown, the success of the model to find the number of leaks is 94%. The success of the model in the case of uncertainty of nodal requirements with the number of known leaks reaches 91% with the increase of leaks and 86% with the number of unknown leaks.https://jhyd.iha.ir/article_176702_3698a6743f366621f29591794864bd68.pdfIranian Hydraulic AssociationJournal of Hydraulics2345-423719120240320Experimental investigation of the effect of transverse waves 1, 2 and 3 modes caused by cylindrical pier groups of the bridge on local scourExperimental investigation of the effect of transverse waves 1, 2 and 3 modes caused by cylindrical pier groups of the bridge on local scour11913417726810.30482/jhyd.2023.399493.1648FAKimiya KamaeiFaculty of Water and Environmental Engineering, Shahid Chamran University of Ahvaz, Ahvaz, Iran0009-0008-6650-7070Mehdi GhomeshiProfessor, Department of Water Structures, Faculty of Water and Environmental Engineering, Shahid Chamran University of Ahvaz, Ahvaz, Iran.0000-0002-8361-1645Mehdi DaryaeeAssistant Professor, Faculty of Water Sciences Engineering, Shahid Chamran University of Ahvaz, Ahvaz, Iran0000-0003-4304-0240Seyed Mahmood KashefiporDepartment of Water Structures, Faculty of Water and Environmental Engineering, Shahid Chamran University of Ahvaz, Ahvaz, Iran0000-0001-7108-828xJournal Article20230603IIntroduction <br />The passage of water through obstacles such as bridge piers in the river, dock piers in the sea, and piers of any other hydraulic structures located in an open channel causes the formation of a boundary layer upstream of the obstacles and the separation of flow lines in the downstream obstacles, leading to the formation of vortex flows. The overlap of the vortices created by each of the obstacles leads to the formation of surface waves whose propagation direction is perpendicular to the flow direction. Under special circumstances when the frequency caused by the vortex of the obstacles is equal to the natural frequency of the structure's oscillation, a resonance mode is created and transverse waves with maximum amplitude are formed along the flume width. The formation of transverse waves with maximum amplitude can affect the safety and stability of hydraulic structures including bridge piers. To this end, recognizing transverse waves can reveal the reasons for the occurrence of some phenomena. Most studies on transverse waves have been conducted in a flume with limited width and a few waves. Thus, by conducting experiments in a wide flume and creating more waves, this study aimed to investigate the effect of waves in different modes on the local scour around the cylindrical piers of bridge.<br /><br />Methodology <br />The experiments were carried out in the Physical and Hydraulic Modeling Laboratory of the Faculty of Water and Environmental Engineering, Shahid Chamran University, Ahvaz, using a rectangular flume with a length of 16 m, a width of 1.25 m, a height of 0.6 m, and a zero slope with glass walls. The flume bed was covered with sediments with an average size of d50 = 0.7 mm. The experiments were conducted with cylindrical pier groups in three stages. The experiments in the first stage were carried out without sediments and the cylindrical piers were placed on a fixed bed without sediments. The first stage experiments aimed to measure the wave parameters (wave amplitude, wave frequency, and flow depth) in the resonance. In the second stage, the sediment experiments were conducted with the formation of transverse waves. After adjusting the water level and forming the desired wave, 4 hours of equilibrium time was considered. Then, the pump was turned off and the end weir was slowly opened. After the complete discharge of the flow, the topography of the bed was measured using a laser meter with an accuracy of 1 mm as 1×1 cm2. The sediment experiments were in the third stage with the removal of transverse waves (control experiments) which were performed to compare with the results of the second stage experiments. A glass sheet was used for this purpose. The glass sheet prevented matching the natural frequency of the channel and the frequency caused by the tier vortex. <br /><br />Results and Discussion <br />To investigate the effect of transverse waves caused by cylindrical piers on the maximum scour depth, each scour in the experiment with transverse waves was compared with the corresponding experiment conducted without transverse waves. The results showed that in wave modes 1, 2, and 3, the maximum scour depth was greater in the case with waves than in the case without waves. The maximum scour depth in wave mode 1 experiments at Froude numbers 0.059, 0.057, and 0.055 was 71, 55, and 54 percent higher than the scour depth in the experiments without waves, and for wave mode 2, the maximum scour depth in the experiments with waves at Froude numbers of 0.117, 0.110 and 0.106 was 90, 76 and 66 percent higher than the maximum scour depth in the experiments conducted without waves. The maximum scour depth in the wave mode 3 experiments with waves at Froude numbers of 0.156 and 0.151 was 70 and 68 percent was higher than the scour depth in the experiments without waves. This study also examined the effect of wave mode on the maximum scour depth. The results indicated that with an increase in the wave number, the maximum scour depth increased in each discharge. On average, the maximum scour depth in wave mode 3 increased by 130 percent compared to wave mode 1 and by 43 percent compared to wave mode 2, and the maximum scour depth in wave mode 2 increased by 60 percent compared to wave mode 1. Also, the maximum scour depth in each wave mode increased with an increase in the wave amplitude, indicating the existence of a direct relationship between the wave amplitude and the maximum scour depth. In addition to the maximum scour depth, transverse waves also affected the scour volume, which was greater in the experiments conducted with waves than in the experiments without waves. On average, the scour volume was 4.3 times in wave mode 1, 3.5 times in wave mode 2, and 9 times in wave mode 3 compared to the wave-free mode.<br /><br />Conclusion <br />The present study examined the effect of transverse waves mode 1, 2, and 3 on the local scour around the cylindrical piers of the bridge. The formation of transverse waves affected the scouring of cylindrical piers, and the maximum scour depth in the experiments conducted with waves was greater than in the experiments without waves. On average, the maximum scour depth increased by 60 percent, 78 percent, and 69 percent in the wave modes 1, 2, and 3 compared to the wave-free mode respectively. Moreover, with an increase in the wave number, the maximum scour depth increased in each discharge, with the maximum and minimum scour depths being found in wave modes 3 and 1, respectively. Overall, the changes in the scour volume followed the same trend as the changes in the maximum scouring depth. On average, the scour volume was 4.3 times in wave mode 1, 3.5 times in wave mode 2, and 9 times in wave mode 3 compared to the wave-free mode.IIntroduction <br />The passage of water through obstacles such as bridge piers in the river, dock piers in the sea, and piers of any other hydraulic structures located in an open channel causes the formation of a boundary layer upstream of the obstacles and the separation of flow lines in the downstream obstacles, leading to the formation of vortex flows. The overlap of the vortices created by each of the obstacles leads to the formation of surface waves whose propagation direction is perpendicular to the flow direction. Under special circumstances when the frequency caused by the vortex of the obstacles is equal to the natural frequency of the structure's oscillation, a resonance mode is created and transverse waves with maximum amplitude are formed along the flume width. The formation of transverse waves with maximum amplitude can affect the safety and stability of hydraulic structures including bridge piers. To this end, recognizing transverse waves can reveal the reasons for the occurrence of some phenomena. Most studies on transverse waves have been conducted in a flume with limited width and a few waves. Thus, by conducting experiments in a wide flume and creating more waves, this study aimed to investigate the effect of waves in different modes on the local scour around the cylindrical piers of bridge.<br /><br />Methodology <br />The experiments were carried out in the Physical and Hydraulic Modeling Laboratory of the Faculty of Water and Environmental Engineering, Shahid Chamran University, Ahvaz, using a rectangular flume with a length of 16 m, a width of 1.25 m, a height of 0.6 m, and a zero slope with glass walls. The flume bed was covered with sediments with an average size of d50 = 0.7 mm. The experiments were conducted with cylindrical pier groups in three stages. The experiments in the first stage were carried out without sediments and the cylindrical piers were placed on a fixed bed without sediments. The first stage experiments aimed to measure the wave parameters (wave amplitude, wave frequency, and flow depth) in the resonance. In the second stage, the sediment experiments were conducted with the formation of transverse waves. After adjusting the water level and forming the desired wave, 4 hours of equilibrium time was considered. Then, the pump was turned off and the end weir was slowly opened. After the complete discharge of the flow, the topography of the bed was measured using a laser meter with an accuracy of 1 mm as 1×1 cm2. The sediment experiments were in the third stage with the removal of transverse waves (control experiments) which were performed to compare with the results of the second stage experiments. A glass sheet was used for this purpose. The glass sheet prevented matching the natural frequency of the channel and the frequency caused by the tier vortex. <br /><br />Results and Discussion <br />To investigate the effect of transverse waves caused by cylindrical piers on the maximum scour depth, each scour in the experiment with transverse waves was compared with the corresponding experiment conducted without transverse waves. The results showed that in wave modes 1, 2, and 3, the maximum scour depth was greater in the case with waves than in the case without waves. The maximum scour depth in wave mode 1 experiments at Froude numbers 0.059, 0.057, and 0.055 was 71, 55, and 54 percent higher than the scour depth in the experiments without waves, and for wave mode 2, the maximum scour depth in the experiments with waves at Froude numbers of 0.117, 0.110 and 0.106 was 90, 76 and 66 percent higher than the maximum scour depth in the experiments conducted without waves. The maximum scour depth in the wave mode 3 experiments with waves at Froude numbers of 0.156 and 0.151 was 70 and 68 percent was higher than the scour depth in the experiments without waves. This study also examined the effect of wave mode on the maximum scour depth. The results indicated that with an increase in the wave number, the maximum scour depth increased in each discharge. On average, the maximum scour depth in wave mode 3 increased by 130 percent compared to wave mode 1 and by 43 percent compared to wave mode 2, and the maximum scour depth in wave mode 2 increased by 60 percent compared to wave mode 1. Also, the maximum scour depth in each wave mode increased with an increase in the wave amplitude, indicating the existence of a direct relationship between the wave amplitude and the maximum scour depth. In addition to the maximum scour depth, transverse waves also affected the scour volume, which was greater in the experiments conducted with waves than in the experiments without waves. On average, the scour volume was 4.3 times in wave mode 1, 3.5 times in wave mode 2, and 9 times in wave mode 3 compared to the wave-free mode.<br /><br />Conclusion <br />The present study examined the effect of transverse waves mode 1, 2, and 3 on the local scour around the cylindrical piers of the bridge. The formation of transverse waves affected the scouring of cylindrical piers, and the maximum scour depth in the experiments conducted with waves was greater than in the experiments without waves. On average, the maximum scour depth increased by 60 percent, 78 percent, and 69 percent in the wave modes 1, 2, and 3 compared to the wave-free mode respectively. Moreover, with an increase in the wave number, the maximum scour depth increased in each discharge, with the maximum and minimum scour depths being found in wave modes 3 and 1, respectively. Overall, the changes in the scour volume followed the same trend as the changes in the maximum scouring depth. On average, the scour volume was 4.3 times in wave mode 1, 3.5 times in wave mode 2, and 9 times in wave mode 3 compared to the wave-free mode.https://jhyd.iha.ir/article_177268_0a58256eea9dc57a89d79345cb3084e7.pdf