scholarly journals Investigation of trapezoidal sharp-crested side weir discharge coefficients under subcritical flow regimes using CFD

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Amir Ghaderi ◽  
Mehdi Dasineh ◽  
Saeed Abbasi ◽  
John Abraham
Keyword(s):  
Discharge Coefficient ◽  
Effective Parameters ◽  
Side Weir ◽  
Discharge Coefficients ◽  
Weir Height ◽  
Crest Length ◽  
Side Weirs ◽  
Upstream Flow ◽  
Water Elevation ◽  
Correlation Factors

AbstractSide weirs are utilized to regulate water surface and to control discharge and water elevation in rivers and channels. Here, the discharge coefficient for trapezoidal sharp-crested side weirs (TSCSW) and their affecting parameters are numerically investigated. To simulate the hydraulic and geometric characteristics of TSCSWs, three weir crest lengths of 15 cm, 20 cm and 30 cm with lengths of 20 cm, 30 cm and 40 cm and with two different sidewall slopes are utilized. The results show that for constant P/B (P: weir height, B: main channel width), the depth of flow along the channel and weir decreases as the crest length increases. Also, with increasing P/y1 ratio (P: weir height, y1: upstream flow depth), the discharge coefficient decreases for small crest lengths and increases for large crest lengths. The results show that for constant T/L ratio (T: passing flow width, L: side weir crest length), increasing the length, height and sidewall slope of a side weir will increase the discharge coefficient. It is observed that as the upstream Froude number increases for side weirs with longer crest lengths, the intensity of deviating flow and kinetic energy over the TSCSW will increase. Finally, some relations with high correlation factors are proposed for obtaining discharge coefficients using the dimensionless parameters of P/y1, T/L and Fr1. Based on proposed relations and sensitivity analysis, it is shown that T/L and P/y1 are the most effective parameters for reducing the discharge coefficient reduction.

scholarly journals Determination Discharge Capacity of Triangular Labyrinth Side Weir Using Multi-Layer Neural Network (ANN-MLP)

2015 ◽  
Vol 10 (Special-Issue1) ◽  
pp. 111-119 ◽  
Author(s):  
Sohrab Karimi ◽  
Hossein Bonakdari ◽  
Azadeh Gholami
Keyword(s):  
Discharge Capacity ◽  
Discharge Coefficient ◽  
Vertex Angle ◽  
Hydraulic Parameters ◽  
Side Weir ◽  
Dimensionless Parameters ◽  
Weir Height ◽  
Crest Length ◽  
Side Weirs ◽  
Mlp Model

statistic indexes have been used to assess the accuracy of the results. The results of the examinations indicate that using MLP model along with simultaneous use of dimensionless parameters for the purposes of estimating discharge coefficient: the ratio of water behind the weir to the channel width (h/b), ratio of weir crest length to weir height (L/W), relative Froude number (F=V/√(2Side weirs are used in open channels to control flood and the flow passing through it. Discharge capacity is one of the crucial hydraulic parameters of side weirs. The aim of this study is to determine the effect of the intended dimensionless parameters on predicting the discharge coefficient of triangular labyrinth side weir. MAPE, RMSE, and Rgy)) and vertex angle (ϴ), offered the best results (MAPE= 0.67, R2= 0.99, RMSE = 0.009) in comparison with other models.

scholarly journals Discharge Coefficient of a C-Type Piano Key Side Weir at 30° and 120° Sections of a Curved Channel

2018 ◽  
Vol 4 (7) ◽  
pp. 1702 ◽  
Author(s):  
Yaser Mehri ◽  
Jaber Soltani ◽  
Mojtaba Saneie ◽  
Mohhamad Rostami
Keyword(s):  
Flood Control ◽  
Discharge Coefficient ◽  
Empirical Relationship ◽  
Effective Parameters ◽  
Level Control ◽  
Side Weir ◽  
Space Limitation ◽  
The Mean ◽  
Coefficient Of Discharge ◽  
Side Weirs

A piano key side weir (PKSW) is a non-linear weir that discharge exceeds linear weirs by increasing the length in width. PKSW can be used in side weirs with space limitation. As side weirs are extensively used in flood control, water level control in rivers, and water supply channels, it is necessary to use PKSW as side weirs. This research discusses the discharge coefficient of a PKSW by assessing a C-type PKSW at 30° and 120° sections of a channel with a longitudinal curve. Dimensional analysis was used for identifying the parameters effective in the discharge coefficient. The effects of these parameters are examined by analysing the effective parameters. Finally, an empirical relationship has been proposed for determining the discharge coefficient based on the dimensionless parameters for calculating the discharge coefficient with the correlation coefficient of 0.88 and the mean error of 0.091. The influence of the parameter on the PKSW is more than that of the remaining parameters: With an increase in the value of this parameter, considering decreases in the length of the deviation and a lack of submerged inlet keys, the coefficient of discharge increases.

scholarly journals Flow characteristics at trapezoidal broad-crested side weir

2015 ◽  
Vol 63 (2) ◽  
pp. 164-171 ◽  
Author(s):  
Jaromír Říha ◽  
Zbyněk Zachoval
Keyword(s):  
Flow Field ◽  
Experimental Research ◽  
Discharge Coefficient ◽  
Empirical Relation ◽  
Flow Characteristics ◽  
Side Weir ◽  
Discharge Coefficients ◽  
Approach Channel ◽  
The Subject ◽  
Side Weirs

Abstract Broad-crested side weirs have been the subject of numerous hydraulic studies; however, the flow field at the weir crest and in front of the weir in the approach channel still has not been fully described. Also, the discharge coefficient of broad-crested side weirs, whether slightly inclined towards the stream or lateral, still has yet to be clearly determined. Experimental research was carried out to describe the flow characteristics at low Froude numbers in the approach flow channel for various combinations of in- and overflow discharges. Three side weir types with different oblique angles were studied. Their flow characteristics and discharge coefficients were analyzed and assessed based on the results obtained from extensive measurements performed on a hydraulic model. The empirical relation between the angle of side weir obliqueness, Froude numbers in the up- and downstream channels, and the coefficient of obliqueness was derived.

Discharge coefficient of a broad crested side weir in an earthen channel

2013 ◽  
Vol 13 (1) ◽  
pp. 166-177 ◽  
Author(s):  
Mohammad Reza Namaee ◽  
Mohammad Sadegh Jalaledini ◽  
Mahdi Habibi ◽  
Saeed Reza Sabbagh Yazdi ◽  
Mona Ghafouri Azar
Keyword(s):  
Discharge Coefficient ◽  
Experimental Tests ◽  
Main Channel ◽  
Channel Width ◽  
Flow Depth ◽  
Irrigation Systems ◽  
Side Weir ◽  
Hydraulic Behavior ◽  
Side Weirs ◽  
Upstream Flow

Side weirs are widely used to divert flows from rivers and channels. However, the hydraulic behavior of this type of weir is complex and difficult to predict accurately. Previous studies on side weirs have generally focused on side weirs in rectangular channels with a smooth bed. However, one of the applications of side weirs is in irrigation systems which have trapezoidal cross sections and significant bed roughness. The present study investigates the hydraulic behavior of a broad crested side weir in an earthen channel with a rough bed under subcritical flow. These investigations showed that the side weir discharge coefficient is influenced by four main parameters which are upstream Froude number, ratio of the main channel width to the upstream flow depth, ratio of the length of the side weir to the main channel width and ratio of side weir height to the upstream flow depth. The results showed that the discharge coefficient of the side weir gives a lower coefficient value compared to other researchers’ equations. Nearly 90 experimental tests were carried out and finally new equations are proposed for prediction of discharge coefficient of a broad crested side weir in an earthen channel under subcritical conditions which can be mainly used in common irrigation systems.

Supercritical flow over a rectangular side weir

2003 ◽  
Vol 30 (3) ◽  
pp. 596-600 ◽  
Author(s):  
Masoud Ghodsian
Keyword(s):  
Discharge Coefficient ◽  
Hydraulic Characteristics ◽  
Height Ratio ◽  
Side Weir ◽  
Supercritical Flow ◽  
Urban Sewage ◽  
Land Drainage ◽  
Weir Height ◽  
Side Weirs ◽  
Sewage Systems

Side weirs are flow-diversion devices widely used in irrigation, land drainage, and urban sewage systems. Hydraulic characteristics of a sharp-crested rectangular side weir under supercritical flow have been studied in this paper. The concept of elementary discharge coefficient for supercritical flow is introduced. The elementary discharge coefficient has been related to head weir height ratio and local Froude number. Suitable equations for the elementary discharge coefficient are introduced.Key words: supercritical flow, sharp crested, rectangular side weir, elementary discharge coefficient.

scholarly journals The Effect of Geometric Parameters of the Antivortex on a Triangular Labyrinth Side Weir

Water ◽  
2020 ◽  
Vol 13 (1) ◽  
pp. 14
Author(s):  
Saeed Abbasi ◽  
Sajjad Fatemi ◽  
Amir Ghaderi ◽  
Silvia Di Francesco
Keyword(s):  
Discharge Coefficient ◽  
Flow Characteristics ◽  
Vertical Axis ◽  
Secondary Flows ◽  
Water Levels ◽  
Effective Length ◽  
Side Weir ◽  
Hydraulic Conditions ◽  
Weir Height ◽  
Side Weirs

Side weirs are important structural measures extensively used, for instance, for regulating water levels in rivers and canals. If the length of the opening is limited, the amount of water diverted out of the channel and the effective length can be increased by applying a labyrinth side weir. The present study deals with numerical simulations regarding the hydraulic performance of a labyrinth side weir with a triangular plan in single-cycle mode. Specifically, six different types of antivortexes embedded inside it and in various hydraulic conditions at different Froude numbers are analyzed. The antivortexes are studied using two groups, permeable and impermeable, with three different heights: 0.5 P, 0.75 P, and 1 P (P: Weir height). The comparison of the simulated water surface profiles with laboratory results shows that the numerical model is able to capture the flow characteristics on the labyrinth side weir. The use of an antivortex in a triangular labyrinth side weir reduces the secondary flows due to the interaction with the transverse vortexes of the vertical axis and increases the discharge capacity by 11%. Antivortexes in a permeable state outperform those in an impermeable state; the discharge coefficient in the permeable state increases up to 3% with respect to the impermeable state. Finally, based on an examination of the best type of antivortex, taking into account shape, permeability, and height, the discharge coefficient increases to 13.4% compared to a conventional labyrinth side weir.

scholarly journals Are We Correctly Using Discharge Coefficients for Side Weirs? Insights from a Numerical Investigation

Water ◽  
2019 ◽  
Vol 11 (12) ◽  
pp. 2585
Author(s):  
Mario Di Bacco ◽  
Anna Rita Scorzini
Keyword(s):  
Neural Networks ◽  
Sensitivity Analysis ◽  
Discharge Coefficient ◽  
Experimental Methodology ◽  
Laboratory Measurements ◽  
Experimental Assessment ◽  
Discharge Coefficients ◽  
Side Weirs ◽  
Water Depths

A key issue in the design of side weirs is the experimental assessment of the discharge coefficient. This can be determined by laboratory measurements of discharge and water depths at the up- and downstream ends of the weir by using De Marchi’s approach, consisting in the solution of the 1D dynamic equation of spatially varied steady flow with non-uniform discharge, under the assumption of energy conservation. This study originates from a recent alarming proliferation of works that evaluate the discharge coefficient for side weirs without clearly explaining the experimental methodology and/or even incorrectly applying modelling approaches, thus generating possible misinterpretations of the results. In this context, the present paper aims to highlight the effects of using oversimplified and/or heterogenous models (relying on different assumptions) for the experimental determination of the discharge coefficient for side weirs. Furthermore, a sensitivity analysis is performed to detect the most influencing hydraulic and geometric parameters on each considered model. The overall results clearly indicate the wrongness of using or building not homogeneous discharge coefficient datasets to obtain and/or compare predictive experimental discharge coefficient formulas. We finally show how neural networks could provide a possible solution to these heterogeneity issues.

Prediction of side weir discharge coefficient by support vector machine technique

2016 ◽  
Vol 16 (4) ◽  
pp. 1002-1016 ◽  
Author(s):  
Hazi Mohammad Azamathulla ◽  
Amir Hamzeh Haghiabi ◽  
Abbas Parsaie
Keyword(s):  
Support Vector Machine ◽  
Discharge Coefficient ◽  
Sensitivity Analyses ◽  
Coefficient Of Determination ◽  
Support Vector ◽  
Good Prediction ◽  
Effective Parameters ◽  
Side Weir ◽  
Svm Model ◽  
Soft Computing Techniques

Side weirs have many possible applications in the field of hydraulic engineering. They are also considered an important structure in hydro systems. In this study, the support vector machine (SVM) technique was employed to predict the side weir discharge coefficient. The performance of SVM was compared with other types of soft computing techniques such as artificial neural networks (ANN) and adaptive neuro fuzzy inference systems (ANFIS). While ANN and ANFIS models provided a good prediction performance, the SVM model with a radial basis function kernel function outperforms them. The best SVM model was developed with a gamma coefficient and epsilon of 15 and 0.3, respectively. The SVM yielded a coefficient of determination (R2) equal to 0.96 and 0.93 for the training and testing data. Sensitivity analyses of the ANN, ANFIS and SVM models showed that the Froude number and ratio of weir length to the flow depth upstream of the weir are the most effective parameters for the prediction of the discharge coefficient.

scholarly journals Experimental study and modelling discharge coefficient of trapezoidal and rectangular piano key weirs

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Munish Kumar ◽  
Parveen Sihag ◽  
N. K. Tiwari ◽  
Subodh Ranjan
Keyword(s):  
Experimental Study ◽  
Random Forest ◽  
Discharge Coefficient ◽  
Predictive Accuracy ◽  
Cost Effective ◽  
Current Data ◽  
Tree Model ◽  
Data Set ◽  
Weir Height ◽  
Crest Length

AbstractCrest length is an important parameter in influencing the discharge handling capacity of a weir. Nonlinear weirs with longer crests are cost effective alternatives for those existing dam structures which are more susceptible to failure due to loss of storage capacity by reservoir silting problem, and insufficiency of the structure in evacuating the updated flow due to the limited space. Piano key weir is a type of nonlinear weir designed in the form of piano keys, over-hanged from both the upstream and the downstream with sloping floors founded on a base or footprint. These weirs can be easily placed over gravity dams due to smaller footprint than labyrinth weirs. The present study’s focus is on the comparative analysis of identical configurations of trapezoidal and rectangular piano key (PK) weirs. The importance of (crest length to width) L/W ratio and weir height (P) in affecting the discharge efficiency of both types of PK weirs is investigated in the experimental study. Furthermore, soft computing approaches are applied to the current data set obtained from both types of weirs by considering discharge coefficient ($$C_{\text{d}}$$Cd) as a function of dimensionless geometric variables of PK weirs. The modelling performance of random forest regression and M5 tree approach is tested in order to estimate the values of discharge coefficient. The results conclude higher predictive accuracy of random forest model over M5 tree model.

scholarly journals Experimental study to estimate the discharge coefficient over inclined side spillway

2020 ◽  
Vol 7 (2) ◽  
pp. 44-54
Author(s):  
Ayat Mehdi kadhim ◽  
Faisal A. Majid
Keyword(s):  
Experimental Study ◽  
Froude Number ◽  
Water Surface ◽  
Discharge Coefficient ◽  
Flow Direction ◽  
Surface Profile ◽  
Side Weir ◽  
Discharge Water ◽  
Water Surface Profile ◽  
Crest Length

Abstract: Weir is usually used in different hydraulic purposes, mainly for head discharge-water relationship in channels. In this research, the flow has been carried out over the side of spillway using three cases of crest inclination by means of increasing one side of the weir a half centimeter each time with constant crest length equal to 15 cm. This means that the angle θ equals to (1.91˚, 3.82˚ and 5.71˚) respectively towards of the flow and is opposite to the flow with decreasing a half centimeter. Also in case of the breadth is horizontal (θ=0), seven cases have been tested. It is known that the greater amount of discharge occurs when the breadth is horizontal (θ=0). In case of the inclination of the weir is inclined opposite to the flow direction, the discharge is greater than that of which the weir inclined towards the flow direction for all cases of inclination. The greater discharge was obtained when decreasing the angle, which is opposite to the flow direction. The amount of discharge over the side of weir decreases by increasing the angle of the slope opposite to the direction of the flow and become more decreasing in case the inclination of side weir towards the flow. In case of increasing the angle of inclination in flow direction, the amount of discharge over side weir will be decreased. The effect of Froude number has also studied with the discharge coefficient and found that, they are proportionally related to each other. Also the water surface profile along the side spillway weir is studied and taken under consideration theoretically and experimentally in this research.

Sign in / Sign up

Export Citation Format

Share Document