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Manouchehr Heidarpour - One of the best experts on this subject based on the ideXlab platform.
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Study of Energy Dissipation and Downstream Flow Regime of Labyrinth Weirs
Iranian Journal of Science and Technology Transactions of Civil Engineering, 2018Co-Authors: Jahanshir Mohammadzadeh-habili, Manouchehr Heidarpour, Sajjad SamieeAbstract:In this study, energy dissipation and downstream flow regime of labyrinth Weirs are investigated. For comparison of results, equation of maximum possible amount of energy dissipation Δ E _max on labyrinth Weirs is obtained by using the specific energy curve. Experimental results supported by dimensional analysis indicated that relative energy dissipation on labyrinth weir Δ E / E _0 is linearly decreased with increasing relative critical depth y _c/ E _0, where E _0 is the total upstream energy. Collision of oblique supercritical flows at the base of nappes created a hydraulic jump on downstream of labyrinth weir. This hydraulic jump stabilized the subcritical flow regime on downstream of weir. Total dissipated energy on labyrinth weir is approximately equal to the maximum possible amount of energy dissipation. Therefore, energy dissipation structures are not required on downstream of the weir. Collision of nappes, circulating flow in created pool behind the nappes, and placing a hydraulic jump on weir downstream face are the main reasons of large energy dissipation on labyrinth Weirs.
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Discharge Coefficient of a Circular-Crested Side Weir in Rectangular Channels
Journal of Irrigation and Drainage Engineering-asce, 2016Co-Authors: Elham Izadinia, Manouchehr HeidarpourAbstract:AbstractSide Weirs are frequently used for water-level control in irrigation systems, sewer networks, and flood protection. Researches on side Weirs have generally focused on determining the hydraulic characteristics of sharp-crested side Weirs. A common type of this weir, which has larger capacity to pass the flow, is the circular-crested weir. To the authors’ knowledge, investigation of hydraulic features of this weir as side weir has been ignored in literature. Based on an experimental model for subcritical flow conditions and under the hypothesis of constant specific energy, the hydraulic characteristics of the circular-crested side weir with various weir heights, widths, and downstream slopes are taken into account to formulate an expression for the discharge coefficient. The results indicate that the upstream Froude number, the weir height to weir length, specific energy to the weir radius, and downstream slope of the weir are the important variables that affect the discharge coefficient of circular...
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Comparison the hydraulic characteristics of finite crest length weir with quarter-circular crested weir
Flow Measurement and Instrumentation, 2016Co-Authors: Jahanshir Mohammadzadeh-habili, Manouchehr Heidarpour, Amir Hamzeh HaghiabiAbstract:Abstract Weirs are used for flow measurement, flow diversion and water level control in open channels. In this study, experiments were conducted on finite crest length weir and quarter-circular crested weir and hydraulic characteristics of two Weirs were compared together. Depending on the ratio of total upstream head H to weir crest length L , flow over the finite crest length weir was undular, parallel to the crest surface or curvilinear. Also, for H / L >1.82, lower nappe separated from the upstream corner of crest and did not reattach to the crest surface. In the range of conducted tests ( H / L H / L >1.52 and H / L >2.2, respectively. This result indicates that quarter-circular crested weir is less sensitive to cavitation danger.
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discharge coefficient of rectangular sharp crested side Weirs part ii dominguez s method
Flow Measurement and Instrumentation, 2014Co-Authors: Sara Bagheri, Abdorreza Kabirisamani, Manouchehr HeidarpourAbstract:Abstract The hydraulic design of a side weir is complicated because the flow conditions vary with distance along the weir, resulting in the 3-D nature of flow over side Weirs. Accordingly, by considering the criticism on De Marchi's discharge coefficient formula (Part I), the present study examines a method proposed by Dominguez for estimating the discharge over the side Weirs under a subcritical flow condition. Further, on the basis of a comprehensive analysis of the available experimental data, the merits of the practical application of the Dominguez's method were evaluated. The results reveal that the fundamental assumptions of Dominguez, e.g ., constant specific energy and linear free surface profile along the side weir in the main channel centerline, are appropriately satisfied. Finally, on the basis of the dimensional analysis, novel correlations were derived for calculating the Dominguez's discharge coefficient with respect to the most significant dimensionless parameters. The estimated results compare well with the results of the model experimentation.
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Hydraulic characteristics of a new weir entitled of quarter-circular crested weir
Flow Measurement and Instrumentation, 2013Co-Authors: Jahanshir Mohammadzadeh-habili, Manouchehr Heidarpour, Hossein AfzalimehrAbstract:Abstract Weirs are used for flow measurement, flood control in reservoirs and water level control in irrigation systems. In this study, a new weir entitled of quarter-circular crested weir is investigated. This weir is geometrically consisted of a quarter-circular crest of radius R, upstream slope α and vertical downstream face. The downstream face of the weir must be ventilated. Discharge coefficient, crest section velocity and pressure profiles, pressure distribution on the crest surface and upper and lower nappe profiles of flow over the quarter-circular crested weir were experimentally investigated. Results indicated that discharge coefficient of the weir is a constant value and equals to 1.261. In the range of H/R
Samira Bagheri - One of the best experts on this subject based on the ideXlab platform.
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discharge coefficient for compound sharp crested side Weirs in subcritical flow conditions
Journal of Hydrology, 2013Co-Authors: A Zahiri, Md H Azamathulla, Samira BagheriAbstract:Side Weirs are one of the most common diversion structures used for flow control, irrigation, drainage networks, and waste-water channels. Side Weirs are generally rectangular sharp crested in form and hence, have some limitations in precise flow measurement. For accurate flow measurement and management in wide range of discharges, use of compound side Weirs are suggested in this study. Experiments have been carried out in a rectangular compound side weir with variable heights and widths. It was determined that discharge coefficient of a compound side weir is a function of upstream Froude number (Fr1), ratio of weighted crest height of weir to upstream water depth w¯/y1 and ratio of weir length to upstream water depth (L/y1). Based on the experimental data and regression modeling, a dimensionless equation has been developed for prediction of the discharge coefficient and an equation has been proposed for estimation of flow discharge in compound rectangular sharp crested side Weirs. Through comparison of results of these equations and experimental data, good agreement was achieved. The mean and maximum relative errors of the discharge equation were −2.3% and 10.7%, respectively.
Ahmet Baylar - One of the best experts on this subject based on the ideXlab platform.
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modeling air entrainment rate and aeration efficiency of Weirs using ann approach
gazi university journal of science, 2009Co-Authors: Ahmet Baylar, Ozgur Kisi, Emin M EmirogluAbstract:The concentration of dissolved oxygen is an important indicator of water quality because aquatic life lives on the dissolved oxygen in the water. A free overfall jet from a weir plunging into downstream water causes entrainment of the air bubbles if the free overfall jet velocity exceeds a certain critical value and hence aeration occurs. This paper investigates the free overfall jets from triangular sharp−crested Weirs and their effect on the air entrainment rate and the aeration efficiency. The artificial neural network models, multi nonlinear and linear regression equations were obtained for the triangular sharp−crested Weirs relating the air entrainment rate and the aeration efficiency to drop height, discharge, and angle in triangular sharp−crested weir. There were good agreements between the measured values and the values obtained using the artificial neural network and multi nonlinear regression models. Key Words : Air entrainment rate, Aeration efficienc,; Dissolved oxygen; Weir, Neural networks.
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The Role of Weir Types in Entrainment of Air Bubbles
2007Co-Authors: Ahmet Baylar, M. Emin EmirogluAbstract:The dominant aeration mechanism in free overfall jet from a weir is that of air bubbles being carried into the biphasic zone when the jet plunges into the receiving pool. The degree of aeration will depend upon the amount of air entrained. This paper investigates effect of the free overfall jets from sharp-crested Weirs, broad- crested Weirs, labyrinth Weirs, and venturi Weirs on the air entrainment. Results pointed that the air entrainment of the Weirs changed depending on weir types. At low drop heights, triangular broad-crested weir had the higher values of the air entrainment rate than the other weir types tested and this advantage becomes more pronounced as the angle in triangular broad-crested weir was decreased. However, at high drop heights, the venturi weir was observed to have the greater values of air entrainment rate than the other weir types tested. The air entrainment rate increased as the throat width of the venturi weir was decreased.
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experimental studies on air entrainment and oxygen content downstream of sharp crested Weirs
Water and Environment Journal, 2006Co-Authors: Ahmet Baylar, Tamer BagaturAbstract:The concentration of dissolved oxygen (DO) is an important indicator of water quality because aquatic life survives on the DO in water. A free overfall jet from a weir plunging into downstream water causes entrainment of air bubbles if the free overfall jet velocity exceeds a certain critical value and hence aeration occurs. This paper investigates the free overfall jets from sharp-crested Weirs and their effect on air entrainment and aeration efficiency. The results indicate that the air entrainment and aeration efficiency of triangular sharp-crested Weirs are significantly better than those for the other sharp-crested weir types. Therefore, the triangular sharp-crested Weirs can be used as highly effective aerators in streams, rivers, constructed channels, fish hatcheries, water treatment plants, etc. Regression equations were obtained for the triangular sharp-crested Weirs relating air entrainment rate and aeration efficiency to drop height, discharge and angle in the triangular sharp-crested weir. There was good agreement between the measured values and the values computed from the predictive equations.
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influence of included angle and sill slope on air entrainment of triangular planform labyrinth Weirs
Journal of Hydraulic Engineering, 2005Co-Authors: Emin M Emiroglu, Ahmet BaylarAbstract:Aeration of water downstream of Weirs is caused by air being carried by the overfalling jet into the downstream receiving pool. The air entrainment characteristics of straight Weirs have been measured and analyzed by a number of investigators. However, labyrinth Weirs, where the weir sill is not straight in planform, thus increasing their length, have received little attention in this respect. This paper investigates the effect of varying the weir-included angle and the weir sill slope on the air entrainment rate of a triangular labyrinth weir. It is demonstrated that the air entrainment rate of a triangular labyrinth weir is better than that of an equivalent straight weir and that this advantage becomes more pronounced as the weir sill slope increases. Regression equations were obtained for triangular labyrinth Weirs relating the air entrainment rate to drop height, weir discharge, weir-included angle, and weir sill slope.
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The effect of broad-crested weir shape on air entrainment
Journal of Hydraulic Research, 2003Co-Authors: M. Emin Emiroglu, Ahmet BaylarAbstract:Aeration is a mass transfer process between the atmosphere and water. Aeration is used for water quality enhancement in sewage treatment plants and in polluted rivers and lakes. This can be enhanced by creating turbulence in the water. Plunging overfall jets from Weirs are a particular instance of producing such turbulence. This paper investigates flows over broad-crested Weirs of different cross-sectional geometry and their effect on the air entrainment rate. It is demonstrated that the air entrainment rate of the 30° triangular broad-crested weir is better than for the other broad-crested Weirs. Moreover, an empirical correlation predicting air entrainment rate was developed for triangular broad-crested Weirs. Good agreement between measured and predicted air entrainment rate values was obtained.
Nihat Kaya - One of the best experts on this subject based on the ideXlab platform.
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discharge coefficient of a semi elliptical side weir in subcritical flow
Flow Measurement and Instrumentation, 2011Co-Authors: Nihat Kaya, Emin M Emiroglu, Hayrullah AgacciogluAbstract:Abstract A labyrinth weir is an overflow weir, folded in plan view to provide a longer total effective length for a given overall weir width. The total length of the labyrinth weir is typically three to five times the weir width. In this study, a semi-elliptical labyrinth weir was used as a side weir structure. Rectangular side Weirs have attracted considerable research interest. The same, however, is not true for labyrinth side Weirs. The present study investigated the hydraulic effects of semi-elliptical side Weirs in order to increase their discharge capacity. To estimate the outflow over a semi-elliptical side weir, the discharge coefficient in the side weir equation needs to be determined. A comprehensive laboratory study including 677 tests was conducted to determine the discharge coefficient of the semi-elliptical side weir. The results were analyzed to find the influence of the dimensionless weir length L / B , the dimensionless effective length L / l , the dimensionless weir height p / h 1 , the dimensionless ellipse radius b / a , and upstream Froude number F 1 on the discharge coefficient. It was found that the discharge coefficient of semi-elliptical side Weirs is higher than that of classical side Weirs. Additionally, a reliable equation for calculating the discharge coefficient of semi-elliptical side Weirs is presented.
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discharge coefficient for trapezoidal labyrinth side weir in subcritical flow
Water Resources Management, 2011Co-Authors: Muhammet Emin Emiroglu, Nihat KayaAbstract:The discharge coefficient of a trapezoidal labyrinth side weir is a function of the Froude number F 1 , the dimensionless effective crest length L/l, the dimensionless weir length L/B, the dimensionless weir height p/h 1 , and the sidewall angle α. A labyrinth weir is an overflow weir, folded in plan view to provide a longer total effective length for a given overall weir width. These Weirs have advantages compared to the straight overflow weir and the standard ogee crest. Previous studies on the subject have generally focused on rectangular side Weirs located on a straight channel. The present study investigates the hydraulic behavior of a trapezoidal labyrinth side weir. The results show that the discharge coefficient of labyrinth side Weirs gives a significantly higher coefficient value compare to that of conventional straight side Weirs. Discharge coefficient of the trapezoidal labyrinth side weir is 1.5 to 5.0 times higher than the conventional straight side weir. Consequently, an equation for the coefficient of discharge is introduced. The results predicted by the equation were shown to be very satisfactory using root mean square error (RMSE), mean absolute error (MAE) and correlation coefficient (R) statistics. Copyright Springer Science+Business Media B.V. 2011
Sara Bagheri - One of the best experts on this subject based on the ideXlab platform.
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numerical modeling of flow field around the labyrinth side Weirs in the presence of guide vanes
ISH Journal of Hydraulic Engineering, 2017Co-Authors: Azam Abdollahi, Abdorreza Kabirisamani, Keyvan Asghari, Hosein Atoof, Sara BagheriAbstract:AbstractSide Weirs are hydraulic structures that are used in irrigation and drainage channels, flood control systems, and wastewater collection networks to divert the flow, isolate the sedimentation, and reduce the bed loads. Labyrinth side Weirs are a type of side Weirs with a higher discharge coefficient compared to the traditional side Weirs. During the last decade, these Weirs have been the interest of different researchers. In this study, triangular labyrinth side Weirs with the groups of guide vanes were modeled numerically using OpenFOAM software. The free surface of subcritical approach flow over the labyrinth side Weirs was modeled using Volume of Fluids method. The standard k-e turbulence model was applied to calculate the flow characteristics. The results of the numerical model are compared well with those of the available experimental data. According to the results, the maximum discharge coefficient of a side weir is obtained when the vane plates are located perpendicular to the flow direction...
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discharge coefficient of rectangular sharp crested side Weirs part ii dominguez s method
Flow Measurement and Instrumentation, 2014Co-Authors: Sara Bagheri, Abdorreza Kabirisamani, Manouchehr HeidarpourAbstract:Abstract The hydraulic design of a side weir is complicated because the flow conditions vary with distance along the weir, resulting in the 3-D nature of flow over side Weirs. Accordingly, by considering the criticism on De Marchi's discharge coefficient formula (Part I), the present study examines a method proposed by Dominguez for estimating the discharge over the side Weirs under a subcritical flow condition. Further, on the basis of a comprehensive analysis of the available experimental data, the merits of the practical application of the Dominguez's method were evaluated. The results reveal that the fundamental assumptions of Dominguez, e.g ., constant specific energy and linear free surface profile along the side weir in the main channel centerline, are appropriately satisfied. Finally, on the basis of the dimensional analysis, novel correlations were derived for calculating the Dominguez's discharge coefficient with respect to the most significant dimensionless parameters. The estimated results compare well with the results of the model experimentation.
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overflow characteristics of circular crested Weirs
Journal of Hydraulic Research, 2010Co-Authors: Sara Bagheri, Manouchehr HeidarpourAbstract:Circular-crested Weirs are one of simplest types of hydraulic structures used for discharge measurement and regulation of open channel flow. In the present study, the flow over a circular-crested weir was simulated with an irrotational vortex to determine the weir discharge coefficient and velocity values over the crest. Two dimensionless parameters including circulation and curvature coefficient were defined and determined experimentally. The results show that these parameters could be presented by power equations. To develop and evaluate the proposed method, physical models of circular-crested Weirs, containing various radii, heights and slopes, were investigated. It was found that this method produces the main features of weir flow reasonably well.
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application of free vortex theory to estimating discharge coefficient for sharp crested Weirs
Biosystems Engineering, 2010Co-Authors: Sara Bagheri, Manouchehr HeidarpourAbstract:Sharp-crested Weirs are commonly used where highly accurate discharge measurements are needed to determine the flow rates in hydraulic laboratories, industrial applications and irrigation systems. Vortex theory and the definitive results obtained by Bazin and Scimeni were used to assess flow over rectangular sharp-crested weir and determine discharge coefficient. Laboratory facilities consisting of sharp-crested Weirs with various widths and heights were used. The proposed theoretical analysis agreed well with the experimental observations. Also, the experimental data indicate that the suggested equation presents reasonable results for a large range of relative weir depths.