Iranian Hydraulic AssociationJournal of Hydraulics2345-42379120140522Evaluation of Hydraulic Jump on Dentate Blocks Stilling BasinEvaluation of Hydraulic Jump on Dentate Blocks Stilling Basin110791010.30482/jhyd.2014.7910FAM. JamGraduate Student, Water Engineering Department, Shiraz University, Shiraz, IranA. MardashtAssistant Professor, Water Department, Shiraz University, Shiraz, IranN. TalebbeydokhtiProfessor, Civil & Environmental Engineering Department, Shiraz University, Shiraz, IranJournal Article20150207The generated kinetic energy at the toe of spillways should be dissipated in the shortest basin to provide normal condition downstream of the river. This research aims to introduce the roughened stilling basin by means of roughness elements (dentate blocks) with new geometry form and arrangement. The study also investigates the effect of different parameters of hydraulic jump on this new stilling basin for the Froude numbers in the range of 11 to 14. The experimental results show a reduction of hydraulic jump parameters on dentate blocks stilling basin while compared to the smooth bed. Length of hydraulic jump and sequent depth was reduced by about 50-60% and 10-12%, respectively. Finally the required roughness length and length of hydraulic jump on dentate blocks stilling basin were compared with the smooth bed basin. For dentate block length of basin was 50-60 percent less and the length of hydraulic jump was only 35-40 percent less than the smooth basin.The generated kinetic energy at the toe of spillways should be dissipated in the shortest basin to provide normal condition downstream of the river. This research aims to introduce the roughened stilling basin by means of roughness elements (dentate blocks) with new geometry form and arrangement. The study also investigates the effect of different parameters of hydraulic jump on this new stilling basin for the Froude numbers in the range of 11 to 14. The experimental results show a reduction of hydraulic jump parameters on dentate blocks stilling basin while compared to the smooth bed. Length of hydraulic jump and sequent depth was reduced by about 50-60% and 10-12%, respectively. Finally the required roughness length and length of hydraulic jump on dentate blocks stilling basin were compared with the smooth bed basin. For dentate block length of basin was 50-60 percent less and the length of hydraulic jump was only 35-40 percent less than the smooth basin.https://jhyd.iha.ir/article_7910_2f8050bb2f3782c0e397d69a48000310.pdfIranian Hydraulic AssociationJournal of Hydraulics2345-42379120140522Investigation on the Effect of Sediment Level on Pressurized Flushing Performance from Reservoirs using Physical ModelInvestigation on the Effect of Sediment Level on Pressurized Flushing Performance from Reservoirs using Physical Model1125791110.30482/jhyd.2014.7911FAM. ShahirniaM.Sc. Student of Water Structures, Department of Water Structures, Faculty of Agricultural Engineering, TarbiatS.A. AyyoubzadehAssociate Professor, Department of Water Structures, Tarbiat Modares University, Tehran, Iran.0816-9445-0002-0000J. Mohamad Vali SamaniProfessor, Department of Water Structures, Tarbiat Modares University, Tehran, Iran.Journal Article20150207In the Pressurized Flushing method, the previously settled sediments at the bottom of the reservoir will be cleaned up and flushed by the downstream water after opening dam’s bottom outlets. The volume of the flushed sediments can be affected by various factors such as the reservoir water surface elevation, flow rate, and sediment elevation at the dam. This study investigates the laboratory scale “Pressurized Flushing” method as well as the impacts of sediment elevation on the efficiency and the dimensions of scour funnel. A physical model was built in Tarbiat Modarres University in order to assess the effects of the aforementioned factors. All the tests were performed at 3 sediment levels and in each sediment level with 3 water depths and 3 flow rates. According to the measured data, there is a direct correlation between the flushing cone dimensions and the sediment elevations. Based on the measured cone dimensions; the greater the sediment discharge at the higher sediment elevations, the greater the dimensions of the flushing cone will be. Furthermore, increasing of the accumulated sediments elevations at the reservoir leads to a higher efficiency of the pressurized flushing. An average increase of 29 percent in sediment elevation leads to 2 percent increase in the efficiency .Moreover, it has been observed that the flushing cone shape in plan view closely resembles a semicircle. Finally, based on the experimental data, dimensionless equations were developed in order to determine the dimensions of the scour funnel. There was a good correlation between the equations and the experimental data.In the Pressurized Flushing method, the previously settled sediments at the bottom of the reservoir will be cleaned up and flushed by the downstream water after opening dam’s bottom outlets. The volume of the flushed sediments can be affected by various factors such as the reservoir water surface elevation, flow rate, and sediment elevation at the dam. This study investigates the laboratory scale “Pressurized Flushing” method as well as the impacts of sediment elevation on the efficiency and the dimensions of scour funnel. A physical model was built in Tarbiat Modarres University in order to assess the effects of the aforementioned factors. All the tests were performed at 3 sediment levels and in each sediment level with 3 water depths and 3 flow rates. According to the measured data, there is a direct correlation between the flushing cone dimensions and the sediment elevations. Based on the measured cone dimensions; the greater the sediment discharge at the higher sediment elevations, the greater the dimensions of the flushing cone will be. Furthermore, increasing of the accumulated sediments elevations at the reservoir leads to a higher efficiency of the pressurized flushing. An average increase of 29 percent in sediment elevation leads to 2 percent increase in the efficiency .Moreover, it has been observed that the flushing cone shape in plan view closely resembles a semicircle. Finally, based on the experimental data, dimensionless equations were developed in order to determine the dimensions of the scour funnel. There was a good correlation between the equations and the experimental data.https://jhyd.iha.ir/article_7911_da21fe7ebb37a5ce201b5d678d7d8517.pdfIranian Hydraulic AssociationJournal of Hydraulics2345-42379120140522An Analytical Solution for Finding the Deflection Point of the Wetted Perimeter – Discharge Curve by Hydraulic Methods for the Determination of Environmental Flow requirementsAn Analytical Solution for Finding the Deflection Point of the Wetted Perimeter – Discharge Curve by Hydraulic Methods for the Determination of Environmental Flow requirements2743791310.30482/jhyd.2014.7913FAM. AminGraduate M.Sc. Student of Water Engineering Department, Imam Khomeini International University, Qazvin, IranA.R. ShokoohiAssociate Professor of Water Resources Engineering, Faculty of Technical and Engineering, Imam Khomeini
International University, Qazvin, IranJournal Article20150207.
In this paper, an analytical solution for determining the minimum water requirement by hydraulic methods (the wetted perimeter approach) is presented. The numerical methods (semi analytical – semi graphical methods) used for solving the non-linear and complex equations of the Hydraulic Method are strongly affected by elements such as the solution method, the increments of independent variable, the geometric properties of the section used to derive the required parameters, and the huge amount of calculations to achieve a reliable result. Indirect approach and reverse solution of the achieved equation to determine the environmental discharge, is another problem when using the Hydraulic Method. The common method of employing an index section or making an index section via averaging different sections, which could impose uncertainty with unknown sources to the solution, is not used in the presented approach. The case study on the Kazemroud River, as a perennial river in the west of Mazanderan Province, showed the complete agreement between the two analytical approach and numerical method. The Hydraulic Method gives the minimum environmental water requirement approximately as much as the annual average discharge of the river, while the Tenant (Montana) Method introduces just 10% of that discharge as the minimum discharge that could lead the river towards a critical situation. If the simplicity of application and insufficient amount of time is the reasons for accepting the Hydrologic Methods like the Tenant Method, the results of this research gives those advantages to the Hydraulic Method that makes it an incomparable approach for the minimum environmental water allocation in rivers..
In this paper, an analytical solution for determining the minimum water requirement by hydraulic methods (the wetted perimeter approach) is presented. The numerical methods (semi analytical – semi graphical methods) used for solving the non-linear and complex equations of the Hydraulic Method are strongly affected by elements such as the solution method, the increments of independent variable, the geometric properties of the section used to derive the required parameters, and the huge amount of calculations to achieve a reliable result. Indirect approach and reverse solution of the achieved equation to determine the environmental discharge, is another problem when using the Hydraulic Method. The common method of employing an index section or making an index section via averaging different sections, which could impose uncertainty with unknown sources to the solution, is not used in the presented approach. The case study on the Kazemroud River, as a perennial river in the west of Mazanderan Province, showed the complete agreement between the two analytical approach and numerical method. The Hydraulic Method gives the minimum environmental water requirement approximately as much as the annual average discharge of the river, while the Tenant (Montana) Method introduces just 10% of that discharge as the minimum discharge that could lead the river towards a critical situation. If the simplicity of application and insufficient amount of time is the reasons for accepting the Hydrologic Methods like the Tenant Method, the results of this research gives those advantages to the Hydraulic Method that makes it an incomparable approach for the minimum environmental water allocation in rivers.https://jhyd.iha.ir/article_7913_cf0fc64f05bcda0763b7d51c49a901a7.pdfIranian Hydraulic AssociationJournal of Hydraulics2345-42379120140522Effect of Non-submerged Rigid Vegetation in Floodplain on Bed Shear Stress around Bridge AbutmentEffect of Non-submerged Rigid Vegetation in Floodplain on Bed Shear Stress around Bridge Abutment4557791410.30482/jhyd.2014.7914FAY. RamezaniAssistant Professor, Department of Water Engineering, Faculty of Agriculture, University of Birjand, Iran.M. GhomeshiProfessor, Department of Hydraulic Structures, Faculty of Water Sciences Engineering, Shahid Chamran
University of Ahvaz, Iran.0000-0002-8361-1645Journal Article20150207Most of bridge abutments are located in floodplains and locating them in the main channels are less common. One of common cases in floodplains is the existence of vegetation cover. Scope of this study is investigation on the effect of non-submerged rigid vegetation in floodplain on bed shear stress around bridge abutment in compound channels. Experiments were carried out for different vegetation densities. Increasing vegetation density was 2 times at each step. Reynolds stresses of , and were used to calculate bed shear stress. Flow velocity was measured by electromagnetic 3D velocimeter at different depths. In this study, because of low flow depth in floodplain, electromagnetic velocimeter cannot measure fluctuations of velocity near the bed. Therefore, Reynolds stresses was calculated at different depths and extrapolation of them to the bed were used to estimate bed Reynolds stresses of , and . Results show that maximum bed shear stress occurred at the upstream corner of the abutment. Bed shear stress development at the upstream corner of the abutment was seen at about a 45 degree angle. In cases that vegetation cover was used, shear stress at the abutment nose decreased and shear stress at the main section of the compound channel increased. Also, with increase in vegetation density, shear stress at the abutment nose decreased. Shear stress at the abutment nose, 3.84 N/m<sup>2 </sup>for the case with no vegetation, 3.41 N/m<sup>2</sup> for the case with s=16, 3.04 N/m<sup>2</sup> for the case with s=12 and 2.61 N/m<sup>2</sup> for the case with s=8, were calculated. The parameter S is the distance between cylinders in centimeter.Most of bridge abutments are located in floodplains and locating them in the main channels are less common. One of common cases in floodplains is the existence of vegetation cover. Scope of this study is investigation on the effect of non-submerged rigid vegetation in floodplain on bed shear stress around bridge abutment in compound channels. Experiments were carried out for different vegetation densities. Increasing vegetation density was 2 times at each step. Reynolds stresses of , and were used to calculate bed shear stress. Flow velocity was measured by electromagnetic 3D velocimeter at different depths. In this study, because of low flow depth in floodplain, electromagnetic velocimeter cannot measure fluctuations of velocity near the bed. Therefore, Reynolds stresses was calculated at different depths and extrapolation of them to the bed were used to estimate bed Reynolds stresses of , and . Results show that maximum bed shear stress occurred at the upstream corner of the abutment. Bed shear stress development at the upstream corner of the abutment was seen at about a 45 degree angle. In cases that vegetation cover was used, shear stress at the abutment nose decreased and shear stress at the main section of the compound channel increased. Also, with increase in vegetation density, shear stress at the abutment nose decreased. Shear stress at the abutment nose, 3.84 N/m<sup>2 </sup>for the case with no vegetation, 3.41 N/m<sup>2</sup> for the case with s=16, 3.04 N/m<sup>2</sup> for the case with s=12 and 2.61 N/m<sup>2</sup> for the case with s=8, were calculated. The parameter S is the distance between cylinders in centimeter.https://jhyd.iha.ir/article_7914_f199204bf5bb170ba680f5e767ea348d.pdfIranian Hydraulic AssociationJournal of Hydraulics2345-42379120140522» Research Note «
Numerical Study of the Effect of Ratio of Radius to Width on Flow Pattern in a 90 Degree Bend» Research Note «
Numerical Study of the Effect of Ratio of Radius to Width on Flow Pattern in a 90 Degree Bend5968791510.30482/jhyd.2014.7915FAS. ElyasiM. S. Graduate Student - Razi University, Kermanshah, Iran.A. EghbalzadehAssistant Professor, Razi University, Kermanshah, Iran – Water and Wastewater Research Center, Razi
University, Kermanshah, Iran.M. Vaghefi. Assistant Professor of Hydraulic Structures, Department of Civil Engineering, Persian Gulf University, Bushehr, Iran.0000-0001-5862-915XM. JavanAssistant Professor, Razi University, Kermanshah, Iran – Water and Wastewater Research Center, Razi
University, Kermanshah, Iran.0000-0002-2509-458XJournal Article20150207Flow 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.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.https://jhyd.iha.ir/article_7915_cb85e8ea4645c3a94033e2c30f2a1910.pdfIranian Hydraulic AssociationJournal of Hydraulics2345-42379120140522» Research Note «
Head Loss of Transient Accelerating Flows for Pipes in Series» Research Note «
Head Loss of Transient Accelerating Flows for Pipes in Series6976791610.30482/jhyd.2014.7916FAS. ZargarMSc. Student, School of Water Science Engineering, Shahid Chamran University, AhwazM. Fathi-MoghadamProfessor, School of Water Science Engineering, Shahid Chamran University, AhwazJournal Article20150207Creation of transient flow in closed conduit is a common phenomenon and also causes serious damage in water supply systems. Flow path leads the system to design of pipes in contraction and expansion series and also gradual and sudden changes in the cross-sections. These changes create negative pressures in pipes specially where pipe diameter changes. The main purpose of this study is experimental investigation of pressure-wave changes in pipes in contraction and expansion series specially where the diameter changes. Tests were carried out with different speeds of valve opening and the results showed that in pipes in contraction series, changes of pressure-wave speed due to pressure changes (that resulted from the opening of the valve at the downstream end of the piping system), at the locations where the diameter changes was more than sections near the valve.Creation of transient flow in closed conduit is a common phenomenon and also causes serious damage in water supply systems. Flow path leads the system to design of pipes in contraction and expansion series and also gradual and sudden changes in the cross-sections. These changes create negative pressures in pipes specially where pipe diameter changes. The main purpose of this study is experimental investigation of pressure-wave changes in pipes in contraction and expansion series specially where the diameter changes. Tests were carried out with different speeds of valve opening and the results showed that in pipes in contraction series, changes of pressure-wave speed due to pressure changes (that resulted from the opening of the valve at the downstream end of the piping system), at the locations where the diameter changes was more than sections near the valve.https://jhyd.iha.ir/article_7916_3f905913da2389f8800473866b0725a5.pdf