Side Weir Research Articles

Machine learning methods for wastewater hydraulics

Wastewater hydraulics problems are frequently addressed by investigation on physical models. Dimensional analysis is a powerful tool that allows discovering essential information about the investigated phenomenon, but in some cases it is affected by significant limitations. In such cases, many issues can be addressed by means of machine learning algorithms, resulting from the theories on pattern recognition and computational learning. In order to show the potential of such an approach, in this study Regression Tree M5P model, Bagging algorithm and Random Forest algorithm were applied to the solution of some complex problems of wastewater engineering: the prediction of energy loss, the pool depth, the air entrainment in a drop manhole, and the forecasting of the lateral outflow in a low crested side weir. The algorithms were trained and tested on data obtained from experimental tests that were carried out at the Water Engineering Laboratory of the University of Cassino and Southern Lazio. In most of the considered cases, regression trees and ensemble methods were able to provide very accurate predictions.

Discharge coefficient of semi-circular labyrinth side weir in subcritical flow

Side weirs are flow diversion or intake devices that are widely used in irrigation and drainage networks and urban sewage systems. Labyrinth weirs have a proven hydraulic advantage due to their increased discharge rate at the same head for a given design condition. A labyrinth weir is defined as a weir crest that is not straight in plan-form. The increased sill length provided by labyrinth weirs effectively reduces upstream head to the particular discharge. In this study, a comprehensive laboratory study was conducted in a physical model of a semi-circular labyrinth side weir and the model is evaluated for three heights and three radii. In this particular study, the hydraulic effects of this shape of side weir in increasing discharge capacity was investigated. The discharge coefficient of semi-circular labyrinth side weirs was determined and the results were analysed to find the influence of the dimensionless parameters of weir height ( w/b ), weir length ( r/b ), nape height (( y 1 −w)/r ), and upstream Froude number ( Fr 1 ) on discharge coefficient ( Cd ), based on the experimental conditions and previous studies. It was found that the discharge coefficient of the semi-circular labyrinth side weir gives a relatively high discharge coefficient value compared to other types of classic side weir positioned on a straight channel. Additionally, reliable equations for calculating the discharge coefficient ( Cd ) of semi-circular labyrinth side weirs are proposed. According to the proposed equation, Cd depends on dimensionless parameters, which are the ratios of r/b, r/w , ( y 1 −w ) /r , ( y 2 −w )/ r and Fr 1 . Keywords: side-weir, discharge coefficient, semi-circular labyrinth side weir, subcritical flow

SIDE WEIR FLOW INVESTIGATION IN A CIRCULAR CHANNEL USING COMPUTATIONAL FLUID DYNAMICS (CFD) FOR SUBCRITICAL FLOW CONDITION

The 3D flow over side weirs is investigated using Computational Fluid Dynamic (CFD). The study aims to assess the capability of ANSYS CFX code for modeling flow characteristics in a circular channel with side weir for subcritical flow condition. Twelve models were studied for some ranges of variables such as discharge, length and height of side weir. The numerical simulation was based on the solution of continuity and momentum equations for three dimensional, incompressible, steady and turbulent flow. The volume of fluid (VOF) method was used to predict the free surface changes and the RNG k-e model was employed for simulating the flow field. The experimental data of Uyumaz and Muslu (1985) were used for verification. For all models, the specific energy is obtained and the average energy difference at the upstream and downstream side of the weir was very small and the assumption of constant energy in the circular channel was acceptable. The numerical results predicted the changes in the water surface profile at the main channel central axis and indicated that the water level rises from upstream to downstream end of the weir. The discharge coefficient (Cd) variation with the upstream Froude number (Fr1) for different weir height and length were studied and it was found that the value of (Cd) decreased with the increase of (Fr1) value. For each side weir length, the variation of (Cd) with the ratio of the weir height to channel diameter (P/D) were studied and it was observed that with the increase of (P/D) ratio the value of the (Cd) increased. The relation between the (Cd) and the ratio of the side weir length to channel diameter (L/D) for different weir height were also investigated. It was noticed that the (Cd) value increased gradually as the (L/D) ratio increased. The combined effects of (Fr1), (P/D) and (L/D) on the (Cd) were studied for all models and an empirical expressions for describing this relation was obtained and it was found that (Cd) was a function of all the above parameter.

Field application studies of the effect of an underground storage chamber using an urban inundation model

Recently, urban inundation disasters resulting from torrential rain have led to serious problems in many countries worldwide. To mitigate the damage of urban inundation, various structural strategies have been carried out, one of which is the creation of underground storage chambers attached to sewerage systems. In this strategy, part of the storm water within a sewer pipe is diverted over the side weir into the storage chamber. The function of this storage chamber is to manage the storm water runoff at a developed site to prevent flooding, and it is essential for providing a temporary storage area for excess storm water. In this study, the differences in the effects of the storage chamber using an urban inundation model due to several conditions such as the rainfall type, changes in the weir shape, installation locations that have different areal features, and changes in the storage capacity volume are verified. Lastly, a suitable installation site is verified via assessments of the inundation damage costs. The results show that the criteria for the degree of mitigation that can be expected in these conditions.

Flow discharge computation over compound sharp-crested side weirs

Side weirs are generally rectangular sharp-crested in form, but for accurate flow measurement and management in a wide range of flow discharges, compound side weirs perform better. Such a commonly used one is rectangular compound side weir, which has a small rectangular weir in lower section for measuring low flow discharges, and a wide rectangular section alongside for measuring higher flows. Determination of discharge coefficient for such a compound side weir is difficult and needs to be calibrated using a large set of laboratory tests. In this paper, based on the practical design method of May et al., a new approach was proposed for predicting flow discharge over compound side weirs. This new approach has been evaluated against experimental data in subcritical flow conditions, and has shown very good agreement with the experimental data, with the mean overall and absolute relative errors being 1.6 and 7.8%, respectively. Because the proposed method is independent of discharge coefficient for overflow rate computation, it will provide a reliable and convenient tool for flow measurement of compound side weirs and their water surface profiles.

Numerical Simulation of Free Surface and Flow Field Turbulence in a Circular Channel with the Side Weir in Subcritical Flow

Abstract When flow surface is higher than of a side weir crest, the overflow spilt over the crest and divert into a side channel. These structures are extensively used in urban sewage disposal networks, water supply systems, and drainage and flood diversion networks. This study simulates stream free surface, discharge over a sharp-crest side weir, and discharge coefficient of a side weir in a circular channel using FLOW-3D software. Numerical model results were compared with the experimental ones and the comparison proved an acceptable consistency between the numerical and experimental results. RNG k-ε turbulence model was used for simulating flow turbulence. The volume of fluid (VOF) method was used in this CFD analysis for predicting changes of flow free surface. Then, the numerical simulation results were examined for discharge coefficient of the side weir and flow free surface for different discharge passing through the main channel. The changes of dividing stream surface from main channel bed toward stream free surface were examined. The concluding section assessed the effect of shape of a circular channel on the pattern and intensity of a secondary flow in the main channel and the impacts of the discharge passing through the circular channel on height of stagnation point and shear stress pattern in the main channel bed.

Optimum Support Vector Regression for Discharge Coefficient of Modified Side Weirs Prediction

Designing procedure of economical and safe side weirs that are used in various hydraulic structures such as intakes and deviation systems, essentially needs the ability to predict the side weirs’ discharge capacity accurately. In this paper, the discharge coefficient of a modified labyrinth side weir was modeled by employing the support vector regression (SVR) method. To find the optimum SVR scenario, eight different kernel functions and six different input combinations were investigated. The accuracy of the SVR models were compared with two nonlinear regression equations from other published studies. The results showed that the SVR model with Polynomial Kernel Function and $$w/L,Fr_{1} /\sin \theta^{\prime},w/Y_{1}$$ and $$w\sin \theta^{\prime}/Y_{1}$$ as input parameters performs better than other models in predicting the discharge coefficient. Where w, L, θ′, and Y 1 are the height of crest, weir length, oblique side-weir included angle, and upstream flow depth, respectively. Also, the results showed that the SVR model with mean square error (RMSE) of 0.050 performs much better than the two other nonlinear regression published equations with RMSE of 0.121 and 0.4270, respectively.

Antivortex Effects on Two-Cycle Trapezoidal Labyrinth Side Weirs

AbstractLabyrinth side weirs can be preferred for the weirs with same opening instead of the other conventional side weirs. However, the vortex occurring in the cycles of the labyrinth side weirs u...

Experimental and Numerical Analysis of Side Weir Flows in a Converging Channel

AbstractThis paper investigates the lateral outflow over a short-crested side weir inserted in a converging rectangular channel with linearly decreasing width in the flow direction. This type of ov...

Sensitivity analysis of the factors affecting the discharge capacity of side weirs in trapezoidal channels using extreme learning machines

Side weirs are installed on the side walls of main channels to control and regulate flow. In this study, sensitivity analysis is planned using Extreme Learning Machines (ELM) to recognize the factors affecting the discharge coefficient in trapezoidal channels. A total of 31 models with 1 to 5 parameters are developed. The input parameters are ratio of side weir length to trapezoidal channel bottom width (L/b), Froude number (Fr), ratio of side weir length to flow depth upstream of the side weir (L/y1), ratio of flow depth upstream of the side weir to the main channel bottom width (y1/b) and trapezoid channel side wall slope (m). Among the models with one input parameter, the model including Froude number modeled the discharge coefficient more accurately (MAPE=4.118, R2=0.835). Between models with two input parameters, the model using Fr and L/b produced MAPE and R2 values of 2.607 and 0.913 respectively. Moreover, among the models with four input parameters, the model containing Fr, L/b, L/y1 and y1/b was the most accurate (MAPE=2.916, R2=0.925).

Experimental research on hydraulics of flood discharge tunnel and improving schemes for choking

Due to the wide range of water levels in reservoir operation, the hydraulic functionality of free surface tunnels in supercritical flow conditions, while discharging beyond design conditions, deserve further studies. To investigate the safe discharging of low drop tunnels, a scale model of a spillway system was built and tested under different flow conditions and structural configurations. Water depth, velocity and flow regime in tunnel and flip bucket reach were measured in experiments. In emptying reservoir operations, a surprising phenomenon was observed; specifically, at low discharges, supercritical flow occurred inside the tunnel while subcritical flow characterized the exit section, with a hydraulic jump forming and moving back into tunnel, forcing it to work under pressure. Critical discharge conditions below which hydraulic jump occurs in the tunnel is theoretically derived by 1D hydraulic analytical computation and experimentally confirmed as q c =0.485q d . To eliminate risk of choked tunnel, a modification is envisioned by setting a torsion angle and a side-weir along the flip bucket section. Experiment results indicate that the combination of a skewed flip bucket and side weir can effectively decrease the outlet water depth, and mitigate the hydraulic jump, avoiding tunnel choking thanks to redirecting the flow into the side weir and to centrifugal force effects. Ski jump flow through the skewed flip bucket and the downstream river regime were also improved.

Effects of Antivortex Structures Installed on Trapezoidal Labyrinth Side Weirs on Discharge Capacity and Scouring

AbstractGreater or more constant discharge can be achieved at lower upstream water depths over the weir crest by increasing the effective lengths of labyrinth side weirs. Labyrinth weirs have uneve...

Study of flow and hydraulic jump along side weirs

Side weirs are widely used for flow control and diversion. Although many studies on sub- and supercritical flows along these weirs have been conducted, only a few research studies have considered the generation of a hydraulic jump along the side weir. Spatially varied flow including a hydraulic jump along the rectangular side weir is studied in this paper. Experimental data for different weir geometries and hydraulic conditions are analysed. Based on the experimental results, new equations for estimating the jump length, the ratio of the conjugate depths and the discharge coefficient are presented. Also, the head loss due to the presence of a hydraulic jump is studied. Furthermore, a numerical model is developed for coupling the water surface profile with a hydraulic jump along the side weir. In this model the lateral outflow momentum is considered, which has been mostly ignored in previous works. The model predicts the location of the hydraulic jump. A comparison of the numerical and experimental results indicates good agreement.

Discharge Coefficient of Rectangular Side Weirs on Circular Channels

AbstractIn this study, the flow turbulence and variations of the supercritical free surface flow in a circular channel along a side weir are simulated as three dimensional using the RNGk-εturbulence model and volume of fluid (VOF) scheme. Comparison between the numerical model and experimental measurements shows that the numerical model simulates the free surface flow with good accuracy. According to the numerical model results, the specific energy variations along the side weir for the supercritical flow regime are almost constant and the energy drop is not significant but by increasing the side weir length the energy difference between the side weir upstream and downstream increases. Next, using the nonlinear regression (NLR) and analysis of the simulation results, some relationships for calculating the discharge coefficient of side weir on circular channels in supercritical flow regime are provided.

Estimation of discharge coefficients of the broad-crested side weir with various levee's side slope of main channel

Estimation of discharge coefficients of the broad-crested side weir with various levee's side slope of main channel

Comparison of Subcritical and Supercritical Flow Patterns Within Triangular Channels Along the Side Weir

Abstract Side weirs with triangular channel are used as flow controlling devices in draining and irrigation networks. By installing a side weir on the main conduits side walls, the runoff overflows from the weir and are conducted toward the diversion channel. In this study, changing of the flow free surface and the turbulence of the flow field in triangular channels with side weir are numerically simulated using volume of fluid (VOF) scheme and RNG k–ε turbulence model. In the present paper, the pattern of the spatially varied flow with decreasing discharge in both subcritical and supercritical flow regimes for triangular channels with side weirs was simulated. The present numerical model has precisely predicted the changes of the water surface and the specific energy. In subcritical regime, the flow depth is from the beginning of the weir toward its end is followed by an increase and in supercritical conditions is followed by a reduction in depth. For both subcritical and supercritical regimes, a drop in the surface in the first third of the weir’s opening and a surface jump in the final third of its length has occurred. Along the mentioned surface jump the amount of the kinetic energy increases and the potential energy reduces. According to results of the simulation, the maximum longitudinal velocity for subcritical flow regime occurs in the first third of the length of the side weir and for supercritical flow regime, almost in the middle of the weir opening happens. In both subcritical and supercritical regimes, the maximum transverse velocity has occurred in the final third of the length of the side weir.

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.

A flow field characterization in a circular channel along a side weir

Side weirs have been used for centuries in urban drainage and flood control for their ability to divert high incoming flow rates. The flow along a side weir may be studied by means of different approaches. However, although the question of side weir has been debating for many decades, there are few studies on the local hydraulic characteristics of the flow along these structures in circular channels.An experimental study of the flow field in a circular channel along a side weir using a commercial TSI Particle Image Velocimetry (PIV) system is shown in this paper. Weakly supercritical flows running into different geometric configurations of the weir were investigated, with Froude numbers varying from 1.1 to 1.6. Free surface profiles have been obtained by an image processing technique. An empirical equation has been proposed for their representation. Longitudinal velocity profiles along the side weir can be well predicted by an entropic approach. Local outflow along the side weir may be represented by an asymmetric curve. The peak outflow generally occurs between the 30% and the 50% of the weir length. The elementary discharge coefficient significantly increases from upstream to downstream. An energy head reduction was observed under the investigated configurations. Most of the head variation occurs in the central part of the weir. Finally, the flow power decreases along the weir according to a non-linear function.A thorough knowledge of the flow field features should allow to improve side weir analysis and design, whatever approach is used for the study.

Support vector regression for modified oblique side weirs discharge coefficient prediction

Accurate determination of discharge coefficient is one of the major concerns in the process of the designing of side weirs. Relation between the modified side weirs discharge coefficient to various geometric and hydraulic situations leads to a high flow complexity around the weirs. In this study, two types of support vector regression (SVR) methods were employed to model the discharge coefficient of a modified triangular side weir. Two types of SVR are obtained by using the radial basis and polynomial as the kernel functions. Six different non-dimensional input combinations with different input variables were used to find the most appropriate one. The results show that both SVR-rbf and SVR-poly methods perform better when the number of input variables is higher, and there is no compaction in the non-dimensional input variables. Comparison between the investigated models shows that the SVR-rbf by RMSE of 0.063 performs much better that SVR-poly by RMSE of 0.084.

Determination of discharge capacity of rectangular side weirs using Schmidt approach

Side weir is a hydraulic structure placed parallel to channel axis or angled to the channel wall in order to divert flow from a channel. Classical De Marchi hypothesis has commonly been used in previous studies to estimate discharge capacity of side weirs. In the present study, the discharge capacity of rectangular side weir was investigated using the Schmidt approach. Competence of average nape height as considered by Schmidt was examined via supplementary laboratory tests. 843 experimental runs were used in the study. In addition, to determine the reliability of the Schmidt approach for calculation of discharge capacity, obtained results were compared with De Marchi and Domínguez approaches. This study showed that Schmidt and Domínguez approaches had similar tendencies for coefficient of discharge, but the scatter data in the De Marchi approach was more significant. It is obvious that Schmidt approach was quite reliable for calculation of the discharge capacity.