Labyrinth Side Weir Research Articles

Numerical modeling of flow field around the labyrinth side-weirs in the presence of guide vanes

Side 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-ε 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 at the downstream end of the weirs across the main channel.

Discharge Coefficient of Triangular and Asymmetric Labyrinth Side Weirs Using the Nonlinear PLS Method

AbstractSide weirs are hydraulic control structures widely used in irrigation and drainage systems as well as wastewater treatment plants. These structures also serve as adjusting/diverting flow structures with a minimum head loss. In the present study, by applying experimental data of more than 400 laboratory tests and using the multivariable nonlinear partial least-squares (PLS) method, three nonlinear equations are proposed for discharge coefficient, CM, of triangular and asymmetric labyrinth side weirs. These equations relate the discharge coefficient to the relevant geometrical and hydraulic dimensionless characteristics of flow. Results indicate that the new proposed equations are more accurate compared to those of former studies, being the best tools to estimate the diverted flow discharge over the side weirs.

Numerical analysis of subcritical flow over two-cycle trapezoidal labyrinth side weir

The side weirs are basic and effective hydraulic structures utilized commonly in irrigation, flood management, drainage and wastewater systems. The labyrinth side weirs have developed in recent years as more effective and efficient mechanism than conventional side weirs. The multi-cycle trapezoidal labyrinth side weirs could increase the side weir performance. The hydrodynamics of these weirs are considerably sophisticated due to the turbulent flow and vortices in the cycles. This paper presents the hydrodynamic behavior of the side weir with two cycles using Computational Fluid Dynamics (CFD) method. The grid convergence index (GCI) was used to demonstrate the mesh sensitivity in the results, and a fine mesh (9mm) selected relatively among the used meshes was applied to computational volume for more accuracy. As the turbulent model, Reynolds Stress Model (RSM) model, which requires more computation effort, was implemented to consider turbulence effects in more detail. Additionally, certain experimental results were used for verification of the numerical results, and the CFD results were considerably consistent with experimental observations. The detailed hydrodynamic results, which were too hard to determine experimentally, were presented to describe the flow properties of this weir. The results indicated that the discharge coefficient decreased with an increase in Froude number. The best performances were obtained with side weir angle, α=30° and weir height, p=20cm among tested values. The results encouraged the use of computational fluid dynamics methods for the further analyses.

Firefly optimization algorithm effect on support vector regression prediction improvement of a modified labyrinth side weir's discharge coefficient

A principal step in designing dividing hydraulic structures entails determining the side weir discharge coefficient. In this study, Firefly optimization-based Support Vector Regression (SVR-FF) is introduced and examined in terms of predicting the discharge coefficient of a modified labyrinth side weir. Ten non-dimensional parameters of various geometrical and hydraulic conditions are defined as the input parameters for the SVR-FF and the side weir discharge coefficient is defined as the output. Improvements in SVR prediction accuracy are determined by comparing SVR-FF with the traditional SVR model. The results indicate that the SVR-FF model with RMSE of 0.035 is about 10% more accurate than SVR with RMSE of 0.039. Thus, combining the Firefly optimization algorithm with SVR increases the prediction model performance.

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

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.

The effect of increasing the number of cycles on the performance of labyrinth side weir

Side weir is one of the most common hydraulic structures, which is used as a deviatory structure in rivers, irrigation and drainage channels and also in urban sewage collection systems. One of the ways to improve the efficiency of the performance of the side weir is changing the geometry of the weir.The effect of deformation and cycle number increase on the hydraulics of the flow was investigated in the side weir, through conducting 360 experiments on the labyrinth weir in three cycles 2, 1 and 4 and the discharge coefficient was obtained for different modes. The results showed that cycle number increase leads to the reduction of flaws such as Eddy flows, decrease of weir input and sudden flow increase along the weir and it also reduces the projection length of the weir. The results indicated that the weirs with cycles 1 and 2 have higher Cm. Also, upon comparison with rectangular weirs, labyrinth weirs increase Cm 1.5 to 3 times and 30% in comparison with modified oblique side weirs (in all cycles).

Discharge Characteristics of a Trapezoidal Labyrinth Side Weir with One and Two Cycles in Subcritical Flow

AbstractA labyrinth weir provides an effective way to increase weir crest length without an associated increase in structure width. Labyrinth side weirs have important advantages compared to conventional side weirs in term of discharge capacity, length of the channel opening, and nappe height over the weir. A different equation is needed for each number of cycles to determine the discharge coefficient of labyrinth side weir. Unlike labyrinth spillways, one or two cycles are mostly sufficient for the labyrinth side weirs to accommodate the required discharge. This study examines the hydraulic characteristics of trapezoidal labyrinth side weirs with two cycles in a subcritical situation and the effect on discharge capacity of using single or multiple cycles in side weirs with the same length openings and crest lengths. The results show that a side weir with one cycle has slightly greater discharge coefficient. In addition, the variation of the discharge capacity was investigated for both one-cycle and two-c...

Prediction of Discharge Coefficient for Trapezoidal Labyrinth Side Weir Using a Neuro-Fuzzy Approach

Adaptive neuro-fuzzy inference system (ANFIS) is considered for flow over trapezoidal labyrinth side weirs located on a straight channel as a substantial part of distribution channels in irrigation systems and treatment units. To estimate the outflow over a trapezoidal labyrinth side weir, the discharge coefficient in the side weir equation needs to be determined in according with the effective dimensionless parameters which is Froude number, the sidewall angle, the ratios of weir length to channel width, weir length to total crest length and weir height to flow depth. 670 laboratory test results are used for determining discharge coefficient of trapezoidal labyrinth side weirs. The performance of the ANFIS model is compared with artificial neural networks (ANN), non-linear regression (NLR) and multi-linear regression (MLR) models. The comparing criteria used for the evaluation of the models’ performances are root mean square errors (RMSE), mean absolute errors (MAE) and determination coefficient (R2) statistics. Comparison results indicated that the ANFIS technique could be successfully employed in modeling discharge coefficient. It is found that the ANFIS model with RMSE of 0.090 in test period is superior in estimation of discharge coefficient than the nonlinear and linear regression models with RMSE of 0.124 and 0.279, respectively.

Triangular labyrinth side weirs with one and two cycles

Labyrinth side weirs provide a potentially effective way to shorten the length of a channel opening with the desired water height, but the discharge coefficient needs to be found experimentally. Experiments were carried out for triangular labyrinth side weirs with one and two cycles in order to obtain the discharge coefficient. The test variables included channel opening, head angle, number of cycles, weir height, upstream water depth and discharge in a subcritical situation. The results show that the discharge coefficient ratio for a triangular labyrinth to a conventional side weir could rise to more than 2 with the same flow and geometric conditions. Relationships for the De Marchi coefficient for subcritical flow in a rectangular channel for triangular labyrinth side weirs (for the two geometries) are introduced as functions of non-dimensional variables of weir and flow. A sensitivity analysis on the measured data is also included.

Determination of capacity of labyrinth side weir by CFD

Side weirs are widely used in irrigation, land drainage, urban sewage systems, flood protection, and forebay pool of hydropower systems by flow diversion or intake devices. The hydraulic behavior of side weirs received considerable interest by many researchers. A large number of these studies are physical model tests of rectangular side weirs. However, in the study, Computational Fluid Dynamics (CFD) models together with laboratory models of labyrinth side weirs were used for determining the discharge capacity of the labyrinth side weir located on the straight channel. The discharges performances obtained from CFD analyses were compared with the observed results for various Froude number, dimensionless nappe height, dimensionless weir width, and weir included angle. The results obtained from both methods are in a good agreement.

Hydraulic Performance of Asymmetric Labyrinth Side Weirs Located on a Straight Channel

This paper details a new design for labyrinth side weirs, which has been tested and analyzed. The proposed geometry for this labyrinth side weir differs from a triangular labyrinth side weir, in that it is asymmetric in plan. The hydraulic behavior of the present labyrinth side weir, with a constant opening length, different weir heights and asymmetric labyrinth side weir included angles has been experimentally investigated in the subcritical situation. Based on the analysis of more than 180 experimental data, an equation for discharge coefficient of the asymmetric triangular labyrinth side weir has been presented. The results show that the discharge coefficient of the asymmetric labyrinth side weir is up to 1.6 and 2.35 times more efficient than a symmetric labyrinth and rectangular side, respectively.

Estimating discharge coefficient of semi-elliptical side weir using ANFIS

Summary A labyrinth weir is defined as a weir crest that is not straight in planform. The increased sill length provided by the semi-elliptical labyrinth side weirs effectively reduces upstream head to the particular discharge. They can therefore be used to particular advantage where the width of a channel is restricted and a weir is required to pass a range of discharges with a limited variation in upstream water level. In this study, the discharge capacity of semi-elliptical side weirs is estimated by using Adaptive-Neuro Fuzzy Inference System (ANFIS). 675 Laboratory test results are used for determining discharge coefficient of semi-elliptical labyrinth side weirs. The performance of the ANFIS model is compared Multiple Linear Regression (MLR) and Nonlinear Regression (NLR) models based on performance evaluation parameters. Comparison results indicated that the ANFIS technique could be successfully employed in modeling discharge coefficient.

Discussion of “Discharge Capacity of Labyrinth Side Weir Located on a Straight Channel” by M. Emin Emiroglu, Nihat Kaya, and Hayrullah Agaccioglu

The declining trend of discharge coefficient in the labyrinth side weir with an increase of flow depth is well-depicted in Fig. 2. In some cases, the effect of flow-depth increase on the decrease of the discharge coefficient of the labyrinth side weir can be so significant after reaching a certain depth that the discharge coefficient of these types of side weirs would be almost equal to that of the corresponding normal rectangular weirs (Fig. 2). In other words, the flow magnification (QL=QN, where QL ¼ discharge over labyrinth side weir and QN ¼ discharge over corresponding linear weir) of the labyrinth side weir proposed by Hay and Taylor (1970) decreases notably with an increase of the nondimensional parameter h=p (where h = main channel depth and p ¼ height of weir crest). This is illustrated in Fig. 3 for a labyrinth side weir with height, span length, and included angle of 10 cm, 60 cm, and 60°, respectively. Moreover, the decrease rate of the discharge coefficient (with an increase of the depth) increases by the decrease of the included angle in a constant height of the side weir. This is evident for labyrinth side weirs with a length of 60 cm and height of 5 cm in Fig. 4. This feature of the labyrinth side weir clearly reveals that in weirs with low included angles (such as 60°), low flow depth results in an increase in the discharge coefficient; however, they are highly vulnerable to the flow depth increase over the weir, and their discharge coefficient decreases notably with an increase of depth flow. This important point should be considered in the design of such weirs.

CFD simulation of free-surface flow over triangular labyrinth side weir

Side weirs are extensively used in the hydraulic and environmental engineering applications. The modeling of free surface flow over a labyrinth side weir is a sophisticated problem in the hydraulic engineering. The water surface profiles over the triangular labyrinth side weirs were investigated by many of the researchers experimentally and theoretically. In this study, the free surface flow over the triangular labyrinth side weir was modeled by using Volume of Fluids (VOF) method to describe the flow characteristics in subcritical flow conditions. A valid method, Grid Convergence Index (GCI) was used to determine the numerical uncertainty of the simulation results. The simulation results were compared with experimental observations, and good agreements were obtained between the both results.

Prediction of lateral outflow over triangular labyrinth side weirs under subcritical conditions using soft computing approaches

This paper presents the results of laboratory model testing of triangular labyrinth side weirs located on the straight open channel flume. The discharge capacity of triangular labyrinth side weirs is estimated by using two different artificial neural network (ANN) techniques, that is, the radial basis neural network (RBNN) and generalized regression neural network (GRNN), and gene-expression programming (GEP), which is an extension to genetic programming. 2500 laboratory test results are used for determining discharge coefficient of triangular labyrinth side weirs. The performance of the ANN and GEP models is compared with multi-linear and nonlinear regression models. Comparison results indicated that the neural computing and gene-expression programming techniques could be employed successfully in modeling discharge coefficient from the available experimental data.

Hydraulic performance of labyrinth side weirs using vanes or piles

In the present study, methods for improving the hydraulic performance of labyrinth side weirs in a rectangular channel are reported based on model experimentation. For this purpose different arrangements and configurations of groups of guide vane plates and piles in the side weir flow field were tested. Experiments were conducted on labyrinth side weirs of different lengths and sill heights fitted in the test section of a rectangular glass-walled channel. Depths of flow were measured in both longitudinal and crosswise directions at regular intervals and their profiles were studied. It was found that the discharge coefficient of the labyrinth side weirs under these conditions gave considerably higher values compared with that of classical simple labyrinth side weirs. Presented in the form of graphs and simplified equations, these new methods enable the designers to improve the hydraulic performance of a given labyrinth side weir. Useful guidance on the layout and construction of vanes and piles across the labyrinth side weir is illustrated and detailed information is given for proper design of these tools. Finally, reliable equations for the discharge coefficient of labyrinth side weirs with regard to the influential parameters of the guide vane plates and piles are presented. The derived expressions are in good agreement with the experimental results.

Use of artificial neural networks for prediction of discharge coefficient of triangular labyrinth side weir in curved channels

Side weirs have been extensively used in hydraulic and environmental engineering applications. The discharge coefficient of the triangular labyrinth side weirs is 1.5-4.5 times higher than that of rectangular side weirs. This study aims to estimate the discharge coefficient (Cd) of triangular labyrinth side weir in curved channel by using artificial neural networks (ANN). In this study, 7963 laboratory test results are used for determining the Cd. The performance of the ANN model is compared with multiple nonlinear and linear regression models. Root mean square errors (RMSE), mean absolute errors (MAE) and correlation coefficient (R) statistics are used as comparing criteria for the evaluation of the models' performances. Based on the comparisons, it was found that the neural computing technique could be employed successfully in modeling discharge coefficient from the available experimental data. There were good agreements between the measured values and the values obtained using the ANN model. It was found that the ANN model with RMSE of 0.1658 in validation stage is superior in estimation of discharge coefficient than the multiple nonlinear and linear regression models with RMSE of 0.2054 and 0.2926, respectively.

INVESTIGATION OF WATER SURFACE PROFILE ALONG LABYRINTH SIDE WEIR LOCATED STRAIGHT CHANNELS

There are a lot of studies related to the rectangular and triangular side weirs located on straight channels. The most of these studies are generally related to discharge coefficient and water level surface of these side-weirs. In this study, the labyrinth weirs have used instead of sharp crested side weirs. A labyrinth weir is defined as a weir crest that is not straight in planform. The increased sill length provided by labyrinth weirs effectively reduces upstream head for a particular discharge. They can therefore be used to a particular advantage where the width of a channel is restricted and a weir is required to pass a range of discharges with a limited variation in upstream water levels. A series of laboratory experiments were conducted in order to determine water surface profiles of the labyrinth side weirs at the straight channel for different labyrinth weir included angles, weir lengths, and crest heights. As a result, it is shown that water surface profile of the labyrinth side weirs is similar to that of classical side weirs. However, it is observed that vortex occurs over the labyrinth side weir for large Froude numbers.

Discharge Coefficient for Trapezoidal Labyrinth Side Weir in Subcritical Flow

The discharge coefficient of a trapezoidal labyrinth side weir is a function of the Froude number F1, the dimensionless effective crest length L/l, the dimensionless weir length L/B, the dimensionless weir height p/h1, 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.

Discharge coefficient of a semi-elliptical side weir in subcritical flow

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.