scholarly journals Energy Dissipation and Hydraulics of Flow over Trapezoidal–Triangular Labyrinth Weirs

Water ◽  
2020 ◽  
Vol 12 (7) ◽  
pp. 1992 ◽  
Author(s):  
Amir Ghaderi ◽  
Rasoul Daneshfaraz ◽  
Mehdi Dasineh ◽  
Silvia Di Francesco
Keyword(s):  
Energy Dissipation ◽  
Discharge Coefficient ◽  
Residual Energy ◽  
Free Flow ◽  
Flow Conditions ◽  
Labyrinth Weir ◽  
Sidewall Angle ◽  
Weir Height ◽  
Downstream Flow ◽  
Labyrinth Weirs

In this work experimental and numerical investigations were carried out to study the influence of the geometric parameters of trapezoidal–triangular labyrinth weirs (TTLW) on the discharge coefficient, energy dissipation, and downstream flow regime, considering two different orientations in labyrinth weir position respective to the reservoir discharge channel. To simulate the free flow surface, the volume of fluid (VOF) method, and the Renormalization Group (RNG) k-ε model turbulence were adopted in the FLOW-3D software. The flow over the labyrinth weir (in both orientations) is simulated as a steady-state flow, and the discharge coefficient is validated with experimental data. The results highlighted that the numerical model shows proper coordination with experimental results and also the discharge coefficient decreases by decreasing the sidewall angle due to the collision of the falling jets for the high value of H/P (H: the hydraulic head, P: the weir height). Hydraulics of flow over TTLW has free flow conditions in low discharge and submerged flow conditions in high discharge. TTLW approximately dissipates the maximum amount of energy due to the collision of nappes in the upstream apexes and to the circulating flow in the pool generated behind the nappes; moreover, an increase in sidewall angle and weir height leads to reduced energy. The energy dissipation of TTLW is largest compared to vertical drop and has the least possible value of residual energy as flow increases.

scholarly journals Prediction of Discharge Capacity of Labyrinth Weir with Gene Expression Programming

2020 ◽  
Author(s):  
Hossein Bonakdari ◽  
Isa Ebtehaj ◽  
Bahram Gharabaghi ◽  
Ali Sharifi ◽  
Amir Mosavi
Keyword(s):  
Gene Expression ◽  
Relative Error ◽  
Discharge Coefficient ◽  
Gene Expression Programming ◽  
Vertex Angle ◽  
Dimensionless Parameters ◽  
Labyrinth Weir ◽  
Predicted Values ◽  
Crest Length ◽  
Labyrinth Weirs

This paper proposes a model based on gene expression programming for predicting discharge coefficient of triangular labyrinth weirs. The parameters influencing discharge coefficient prediction were first examined and presented as crest height ratio to the head over the crest of the weir (p/y), crest length of water to channel width (L/W), crest length of water to the head over the crest of the weir (L/y), Froude number (F=V/√(gy)) and vertex angle () dimensionless parameters. Different models were then presented using sensitivity analysis in order to examine each of the dimensionless parameters presented in this study. In addition, an equation was presented through the use of nonlinear regression (NLR) for the purpose of comparison with GEP. The results of the studies conducted by using different statistical indexes indicated that GEP is more capable than NLR. This is to the extent that GEP predicts the discharge coefficient with an average relative error of approximately 2.5% in such a manner that the predicted values have less than 5% relative error in the worst model.

scholarly journals Energy Dissipation of Type a Piano Key Weirs

Water ◽  
2020 ◽  
Vol 12 (5) ◽  
pp. 1253
Author(s):  
Kam R. Eslinger ◽  
Brian M. Crookston
Keyword(s):  
Energy Dissipation ◽  
Hydraulic Structure ◽  
Type A ◽  
Residual Energy ◽  
Published Data ◽  
Hydraulic Efficiency ◽  
Support Design ◽  
Small Footprint ◽  
Piano Key Weir ◽  
Labyrinth Weirs

A Piano Key weir (PK weir) is a nonlinear, labyrinth-type weir well suited for rehabilitation projects due to a relatively small footprint and the ability to pass large discharges for lesser upstream-head values when compared with other weir types. A critical component of a hydraulic structure is the energy-dissipative properties. Currently, information and guidance is limited, with previous energy dissipation studies of PK weirs primarily of specific projects. Therefore, to document and quantify energy dissipation, four laboratory-scale Type A PK weir models with different width ratios (Wi/Wo) were studied, with 255 tests comprising this new dataset, along with detailed observations of the flow field. Results were compared to existing published data regarding energy dissipation downstream of trapezoidal and rectangular labyrinth weirs. To support design efforts, two equations, both functions of head-water ratio (H/P) and Wi/Wo, are proposed to predict the relative residual energy downstream of PK weirs. The energy dissipation of PK weirs is largest at low flows and decreases in a logarithmic-like manner as flow increases. PK weirs with increased hydraulic efficiency, caused by an increase in Wi/Wo, resulted in slightly smaller energy dissipation values within the range 0.2 ≤ H/P ≤ 0.8. The energy dissipation of PK weirs was found to be relatively constant, independent of Wi/Wo, and in the ranges 0.07 ≤ H/P ≤ 0.2 and 0.8 ≤ H/P ≤ 0.95.

scholarly journals Application of SVM, ANN, GRNN, RF, GP and RT models for predicting discharge coefficients of oblique sluice gates using experimental data

2020 ◽  
Author(s):  
Farzin Salmasi ◽  
Meysam Nouri ◽  
Parveen Sihag ◽  
John Abraham
Keyword(s):  
Discharge Coefficient ◽  
Performance Metrics ◽  
Experimental Results ◽  
Free Flow ◽  
Support Vector ◽  
Flow Conditions ◽  
Discharge Coefficients ◽  
Gate Opening ◽  
Experimental Apparatus ◽  
Inclined Angle

Abstract Gates are commonly used to adjust water flow in open channels. By using an oblique/inclined gate, the water transferring capacity of open irrigation canals can be increased. Investigation of free and submerged discharge coefficients for inclined sluice gates is the focus of the present study. First an experimental apparatus incorporating an inclined gate was created. The inclined angle (β) and gate opening (a) were experiment variables, and the five inclination angles include: 0° (vertical gate), 15°, 30°, 45° and 60°. Experimental results showed a greater convergence of flow lines under the gate and increasing the gate angle causes the discharge coefficient to increase. Also experiments showed that increasing the submergence rate (yt/a), decreases the inclined gate discharge coefficient. Performance metrics were created for the experimental results. The metrics utilized Gaussian process (GP) regression, Support Vector Machine (SVM), artificial neural networks (ANN), generalized regression neural network (GRNN), Random Forest (RF) regression and Random Tree (RT) based models which were used to predict discharge coefficients (Cd) in both submerged and free flow conditions. The model input parameters were the ratio of the upstream water depth to gate opening (y/a) and the inclined angle (β) for free flow and also the submergence rate (yt/a) for submerged flow. The prediction models show that the ANN model in free flow conditions has the following performance metrics: Coefficient of determination, R2= 0.9957, Root Mean Square Error (RMSE) = 0.0044, and Mean Absolute Error (MAE) = 0.0017. The performance metrics for submerged flow conditions were R2 = 0.9922, RMSE = 0.0079 and MAE = 0.0054. The ANN approach is the most accurate model compared to the others.

Study of Energy Dissipation and Downstream Flow Regime of Labyrinth Weirs

2017 ◽  
Vol 42 (2) ◽  
pp. 111-119 ◽  
Author(s):  
Jahanshir Mohammadzadeh-Habili ◽  
Manouchehr Heidarpour ◽  
Sajjad Samiee
Keyword(s):  
Energy Dissipation ◽  
Flow Regime ◽  
Downstream Flow ◽  
Labyrinth Weirs
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