Discharge In Open Channel Research Articles

Transport and risk of airborne pathogenic microorganisms in the process of decentralized sewage discharge and treatment

Sewage treatment processes are a critical anthropogenic source of bioaerosols and may present significant health risks to plant workers. Compared with the specialization and scale of urban sewage treatment, many decentralized treatment models are flexible and extensive. These treatment facilities are usually close to residential areas owing to the pipe network layout and other restrictions. Bioaerosols generated by these facilities may present a serious and widespread occupational and non-occupational exposure risk to nearby residents, particularly the elderly and children. An understanding of the characteristics and exposure risks of bioaerosols produced during decentralized sewage treatment is lacking. We compared bioaerosol emission characteristics and potential exposure risks under four decentralized sewage discharge methods and treatment models: small container collection (SCC), open-channel discharge (OCD), single household/combined treatment (SHCT), and centralized treatment (CT) in northwest China. The OCD mode had the highest bioaerosol production, whereas the CT mode had the lowest. The OCD model contained the most pathogenic bacterial species, up to 43 species, including Sphingomonas, Pseudomonas, Cladosporium, and Alternaria. Risk assessments indicated bioaerosol exposure was lower in the models with sewage treatment (SHCT and CT) than in those without (SCC and OCD). Different populations exhibited large variations in potential risks owing to differences in time spent indoors and outdoors. The highest risk was observed in males exposed to the SCC model. This study provides a theoretical basis and theories for the future joint prevention and control of the bioaerosol exposure risk from decentralized sewage treatment.

Discharge formula based on brink depth over sharp-crested weirs

Abstract Weirs are among the most essential hydraulic structures for measuring water discharge in open channels. The prediction of water discharge over weirs should be as precise and straightforward measured as feasible. The experimental investigation of flow prediction over varied heights of a conventional rectangular sharp-crested weir was conducted in the present work. The investigation evaluated five ratios of weir height to length, P/b, of 0.33, 0.4, 0.47, 0.53, and 0.6, different water discharges, Q, of up to 17.25 L/s, and different bed slopes, S, between 0.001 and 0.01. The experiment's findings reveal that a change in the bed slope has no significant effect on the brink depth, hb, for a constant water discharge. However, it influences the head over the weir, h, which is usually measured upstream of the weir location and used to predict water discharge. A simple, accurate formula was developed for predicting water discharge over rectangular sharp-crested weirs depending on the brink depth with mean absolute percent error (MAPE) and root-mean-square error (RMSE) of 1.714% and 0.229, respectively. In addition to having a simple form, the developed formula performs well, is unaffected by the bed slope, and applies to a wide range of h/P values, from 0.158 to 0.945.

Discharge estimation using brink depth over a trapezoidal-shaped weir

A weir is an accurate hydraulic structure for estimating water discharge in open channels and rivers. It can be constructed with a standard shape with vertical upstream and downstream faces or it can be modified by inclining one or both weir faces to enhance its hydraulic characteristics. In this study, the feasibility of using the brink depth over a trapezoidal-shaped weir (yb) for discharge estimation was experimentally investigated for free flow conditions. The experimental work involved the use of three lengths of the weir crest, L (10, 20, and 30) cm, and four different slopes (37°, 54°, 75°, and 90°) for both upstream and downstream faces, each with different water discharge. In addition, the effect of channel bed slopes on the water head over the weir (h) and the brink depth (yb) was investigated. The results indicated that the (yb) can be used for discharge estimation with good accuracy for a trapezoidal-shaped weir instead of water head over the weir (h), which is usually used in estimating water over the weir, as (yb) does not affect by the channel bed slope and insignificantly affected by changing the upstream and/or downstream face angle, contrary to the (h). Hence, an empirical equation for estimating water discharge based on (yb) with different upstream and downstream slopes was developed and examined using some available previous studies data. The mean absolute percentage error (MAPE) between (yc/L) with (yb/L) and between the measured and estimated discharge is 4.73% and 7.02%, respectively.

Data-driven modeling of sluice gate flows using a convolutional neural network

Abstract Predicting the flow field around sluice gates is essential for controlling water levels and discharges in open channels and rivers. Smooth particle hydrodynamics (SPH) models can satisfactorily reproduce such free-surface flows, but they typically require long computational time and extensive computational resources. In this work, we propose a convolutional neural network (CNN) to predict the flow field around a sluice gate. A validated SPH model is used to carry out extensive simulations, and the generated data set is used to train and test CNN-based models. The results demonstrated that the developed CNN can accurately reproduce sluice gate flows, with R2 values exceeding 90% and significantly reducing the computational costs. Furthermore, various traditional machine learning algorithms comprising adaptive neuro-fuzzy inference system, genetic programing, multigene genetic programing, and one-dimensional CNN were also evaluated, and a comparison of the results showed that the developed CNN performed better than the traditional data-driven algorithms in predicting sluice gate flows. Therefore, the proposed method is a promising tool for providing rapid prediction of the spatial distribution of flow fields near the sluice, and potentially for predicting other spatially distributed hydrologic variables.

Prediction of Manning's coefficient of roughness for high-gradient streams using M5P

Abstract The coefficient of Manning's roughness (n) has been generally implemented in the determination of depth and discharge in open channels and canals. This study unravels the novel idea and potential of Random Forest (RF), M5P, and Random Tree (RT) approaches to evaluate and predict the coefficient of Manning's roughness for hydraulic designing. To achieve this purpose, 42 observations were collected for high-gradient streams in Colorado, USA. All the observations were from boulder-bed, cobble and high gradient (S > 0.002 m/m) streams within bank flows. In order to ascertain the best model, the above-mentioned approaches were evaluated and compared using performance evaluation indices such as mean absolute error (MAE), coefficient of correlation (CC), and root mean square error (RMSE). Outcomes of performance evaluation indices revealed that the proposed pruned M5P approach outperformed other applied models for predicting the coefficient of Manning's roughness for hydraulic designing with CC = 0.7858, 0.7910, RMSE = 0.0195, 0.0195, and MAE = 0.0157, 0.0165 for model development and validation period, correspondingly. Furthermore, Taylor diagram and Box plot also suggest that the M5P based approach works better than RF and RT based approaches for predicting the coefficient of Manning's roughness for high-gradient streams using the given data set.

Determination of Manning's Roughness Coefficient in Bijayapur Irrigation Canal, Kaski, Nepal

The discharge in irrigation canal is to be determined for the proper allocation of water to the fields as per the crop-water requirement. Manning’s roughness coefficient is one of the major important parameters for estimating discharge in open channel. The purpose of this research is to determine Manning’s roughness coefficient in open channel flow by means of measuring velocity, cross-section, bed slope using Manning’s equation. It also discusses how it varies along with various aspects of channel geometry and draws useful conclusion from the analysis. The investigation was carried out in the Bijayapur Irrigation System which is situated in Kaski district of Nepal. The velocity was measured using current-meter and discharge was calculated from the area velocity methods. Roughness coefficient was calculated using the Manning’s equations for the uniform flow in open channel. The average value of Manning’s roughness coefficient at Sakneri and Bijayapur computed from this study was found 0.028 and 0.037, respectively. The roughness coefficient, however, being a parameter representing the integrated effects of the channel cross-sectional resistance, the result of this study shows the higher value of roughness coefficient for the material (cement rubble masonry) used in the construction of canal. The higher value of roughness coefficient might be due to uneven bed and poor condition of banks as observed during the study. The greater value of roughness coefficient definitely reduces discharge which leads to the tail end deprivation in the command area.

Determination of Manning's Roughness Coefficient in Bijayapur Irrigation Canal, Kaski, Nepal

The discharge in irrigation canal is to be determined for the proper allocation of water to the fields as per the crop-water requirement. Manning’s roughness coefficient is one of the major important parameters for estimating discharge in open channel. The purpose of this research is to determine Manning’s roughness coefficient in open channel flow by means of measuring velocity, cross-section, bed slope using Manning’s equation. It also discusses how it varies along with various aspects of channel geometry and draws useful conclusion from the analysis. The investigation was carried out in the Bijayapur Irrigation System which is situated in Kaski district of Nepal. The velocity was measured using current-meter and discharge was calculated from the area velocity methods. Roughness coefficient was calculated using the Manning’s equations for the uniform flow in open channel. The average value of Manning’s roughness coefficient at Sakneri and Bijayapur computed from this study was found 0.028 and 0.037, respectively. The roughness coefficient, however, being a parameter representing the integrated effects of the channel cross-sectional resistance, the result of this study shows the higher value of roughness coefficient for the material (cement rubble masonry) used in the construction of canal. The higher value of roughness coefficient might be due to uneven bed and poor condition of banks as observed during the study. The greater value of roughness coefficient definitely reduces discharge which leads to the tail end deprivation in the command area.

Experimental Investigation of Discharge Coefficient of Smooth-Crested Pattern Notches Entitled of Various Profiles

Notches are common and useful devices in flow measurements in open channels. Precise estimation of discharge and coefficient of discharge in open channels is critical in hydraulic structures. Overestimation of discharge may cause failure to the structure. If the discharge is underestimated, it may not fulfill the design requirements. Present work focus on systematic experimentation for patterned triangular notches with different geometrical parameters. The main objective is to optimize the profile of patterned triangular notch to ensure the optimum discharge and coefficient of discharge. Governing equation for coefficient of discharge for patterned triangular notch is established based on the principle of notch flow, with consideration of the water depth, height and width of the notch. The impacts of various geometrical parameters of patterned triangular notch on the discharge coefficient are investigated. The new shape of notch is entitled to increase the coefficient of discharge, and to improve their hydraulic characteristics. Results indicated that discharge coefficient of the patterned shape triangular notch is greater than conventional notch.

Application of LSPIV to measure supercritical flow in steep channels with low relative submergence

Measuring flow discharge has always been one of the most important concerns of water experts. To measure discharge in streams using velocity-area method it is necessary to quantify average velocity of the flow. It is not feasible to measure velocity by contact approaches like current meters under certain conditions such as in flood periods or for very shallow flows. Flow surface image velocimetry methods as non-intrusive solutions have recently been widely utilized to measure discharge in open channels. One of these methods is a variety of PIV method named LSPIV which has been very popular due to the elimination of laser application. In this study, LSPIV was used to measure 2D velocity field over the surface of steep supercritical flow. The obtained surface velocity data were used to calculate Velocity Index (VI) which is multiplied by surface velocity to convert it to mean velocity and subsequently flow discharge. Also, a few relations were proposed to calculate the VI according to the slope and relative submergence. Since, Velocity Index has been so far mostly studied for subcritical conditions, results of this study may be applied for measuring supercritical flows. Eventually, the proposed method was verified to be used for discharge measurement and was proven quite precise in this regard.

Manning roughness coefficient in vegetated open channels

ABSTRACT Manning equation is one of the most common equations used in estimating the mean velocity and discharge in open channels. The equation depends on some measured hydraulic parameters as water surface slope and hydraulic radius of open channel cross-section in addition to the Manning roughness coefficient. Estimating the value of Manning`s roughness coefficient is dependent on the nature of the channel, the number of obstacles that resist the channel flow and the field engineers experience. In vegetated channels, the percentage of infestation seems to be the most effective parameter on the roughness coefficient value. Through this study, based on laboratory investigation and physical model several trials were conducted to deduce an equation to predict the value of the Manning`s roughness coefficient in the vegetated channel based on measured parameters as weed infestation percentage, water surface slope. Two simple equations were deduced based on these parameters to practically estimate the value of the Manning roughness coefficient in vegetated open channels. The results of these equations were successfully verified using field measurements.

A robust approach for rating curves estimation in open channels using isovel contours

ABSTRACT The use of reliable stage-discharge curves is one of the most important issues in the management of water resources and river engineering. Discharge measurement in natural rivers is generally difficult and accompanied by errors. The use of new models has an effective role in reducing the time and cost associated with hydrometry. The purpose of the present study is to introduce a new method to estimate discharge in open channels using a novel method that is based on the isovel technique. The significant aspect of the present method is its inherent simplicity, which does not need any calibration. Using the proposed method, it is possible to estimate the stage-discharge curve in the whole section by only using discharge information from just one arbitrary water level. Theoretical discharge can be obtained through a general relationship, which is composed of some parameters with unknown powers. According to the number of parameters as well as the geometric cross-sections, 225 different relations are extracted. The minimization process of error between the observed and estimated data is used to select the most accurate relationship. For validation, data from eight river cross-sections are used. Results indicated that the mean value of error is within 7.2%. Amongst the advantages of the proposed method is that it can be applied to all kinds of hydraulic cross-sections, even those with non-uniform bed roughness distributions.

Estimating the Bed-Load Layer Thickness in Open Channels by Tsallis Entropy.

In the research field of river dynamics, the thickness of bed-load is an important parameter in determining sediment discharge in open channels. Some studies have estimated the bed-load thickness from theoretical and/or experimental perspectives. This study attempts to propose the mathematical formula for the bed-load thickness by using the Tsallis entropy theory. Assuming the bed-load thickness is a random variable and using the method for the maximization of the entropy function, the present study derives an explicit expression for the thickness of the bed-load layer as a function with non-dimensional shear stress, by adopting a hypothesis regarding the cumulative distribution function of the bed-load thickness. This expression is verified against six experimental datasets and are also compared with existing deterministic models and the Shannon entropy-based expression. It has been found that there is good agreement between the derived expression and the experimental data, and the derived expression has a better fitting accuracy than some existing deterministic models. It has been also found that the derived Tsallis entropy-based expression has a comparable prediction ability for experimental data to the Shannon entropy-based expression. Finally, the impacts of the mass density of the particle and particle diameter on the bed-load thickness in open channels are also discussed based on this derived expression.

A Simulation–Optimization Technique to Estimate Discharge in Open Channels Based on Water Level Data Alone: Gradually Varied Flow Condition

Discharge estimation in open-channel hydraulics is required for a variety of purposes including design of hydraulic structures, reservoir routing, water pricing and payment. This estimation procedure lasts for almost two centuries. Nowadays, research interest in discharge estimation methods based on the water level data alone has grown due to the drawbacks of direct velocity measurement. Recent trend in this field is switched from physical measurement to numerical by linking a gradually varied flow equation solver with either structured or random search optimization algorithm to obtain channel roughness and associated discharge. In this paper, in reference to the existing research gaps, the authors intend to evaluate the performance and accuracy of the above proposal for both M1 and M2 water surface profiles in both hypothetical and real-world settings. In this regard, a number of water surface profiles with various discharges, slopes and bed roughness were synthetically generated and/or measured on a very fine stream-wise grid in a laboratory flume for both M1 and M2 profiles. This enabled us to assess and investigate the impact of hydraulic conditions, simulation and optimization parameters on discharge estimation. The results show that, while synthetic water depth data on M1 and M2 can be effectively utilized to compute channel discharge, the discharge estimation based on laboratory data has a high accuracy for M2 profiles compared with M1 profiles. As the roughness coefficient and consequently the error in water level data measurements increases, the accuracy of the proposed method decreases. In addition, the aforementioned method has better results in steep waterways where the subcritical flow regime acquires high Froude number. Moreover, the results show that the values of initial guess and upper bounds of n and Q are not important in M2 water surface profiles. However, for M1, using initial guesses and upper bounds approximately near to the actual known’s n and Q gives better results. In addition, by increasing the distance between nodes and consequently decreasing the number of required water level data, the accuracy of discharge estimation decreases. In conclusion, both private and government sectors in water industry can benefit from water level monitoring to estimate discharge for various applications in real-world settings.

Suspended Sediment Concentration and Discharge in Open Channels Using Rényi Entropy

The vertical distribution of suspended sediment concentration in an open channel is modeled using Rényi entropy. The model, derived by invoking the principle of maximum entropy, is tested against field and laboratory observations by taking into account nonzero sediment concentration at the surface, and is also compared with other entropy-based and deterministic sediment concentration models. The proposed model is found to be in good agreement with observed data, and its prediction accuracy is superior to that of the other models. It is expressed in terms of a dimensionless entropy parameter that is constant along any vertical in a given river cross section. Errors, namely relative bias (RBIAS) and root-mean-square error (RMSE), are calculated for each of the data sets to validate the model and establish its superiority. It is observed that the RMSE of the present model varies from 0.045 to 4.197 g/L, and from 16.438 to 74.470 g/L, for experimental and field data, respectively, which lie within reasonable limits. In addition, the suspended sediment discharge per unit width is calculated using the Rényi entropy-based models of velocity and sediment concentration. The computed and observed values of sediment discharge are calculated from experimental observations, and it is found that the model can estimate observed values well.

Uso de modelo hidrodinâmico para determinação da vazão a partir de medições de nível

RESUMO O uso de modelos hidrodinâmicos para a determinação das vazões em cursos d’água tem crescido nos últimos anos devido aos problemas relativos à utilização do método da curva-chave para monitoramento das vazões. Este trabalho tem por objetivo desenvolver um método para determinação das vazões em canais abertos utilizando algoritmos evolucionários multiobjetivos (NSGA-II) e medições de nível da superfície livre associadas a um modelo hidrodinâmico. Dados obtidos de ensaios em um canal experimental de laboratório foram utilizados para calibração e validação do modelo. O algoritmo de otimização NSGA-II apresentou excelentes resultados, obtendo-se coeficientes de Nash-Sutcliffe superiores a 0,99 tanto para a calibração quanto para a validação do modelo hidrodinâmico. As vazões calculadas pelo modelo hidrodinâmico apresentaram uma variação de até 150% para um mesmo nível quando comparadas às vazões estimadas pela curva-chave, o que demonstrou que o uso da curva-chave para medição de vazão em regime variável apresenta erros elevados.

Fuzzy Linear Regression for the Time Series Data which is Fuzzified with SMRGT Method

Our work on regression and classification provides a new contribution to the analysis of time series used in many areas for years. Owing to the fact that convergence could not obtained with the methods used in autocorrelation fixing process faced with time series regression application, success is not met or fall into obligation of changing the models’ degree. Changing the models’ degree may not be desirable in every situation. In our study, recommended for these situations, time series data was fuzzified by using the simple membership function and fuzzy rule generation technique (SMRGT) and to estimate future an equation has created by applying fuzzy least square regression (FLSR) method which is a simple linear regression method to this data. Although SMRGT has success in determining the flow discharge in open channels and can be used confidently for flow discharge modeling in open canals, as well as in pipe flow with some modifications, there is no clue about that this technique is successful in fuzzy linear regression modeling. Therefore, in order to address the luck of such a modeling, a new hybrid model has been described within this study. In conclusion, to demonstrate our methods’ efficiency, classical linear regression for time series data and linear regression for fuzzy time series data were applied to two different data sets, and these two approaches performances were compared by using different measures.

Predictive modeling of discharge of flow in compound open channel using radial basis neural network

Predicting the flow discharge in open channel is the main parameters in the flood management. The concept of the compound open channel is the accurate approach for modeling the natural streams. Several ways as analytical approaches and artificial intelligence methods have been proposed for predicting the discharge in rivers in term of compound open channel concepts. In this paper the single channel method (SCM), coherence method (COHM), and divided channel method (DCM) as common analytical approaches were used to predict the discharge in the compound open channel and in follow to achieve more accuracy in flow discharge prediction the radian basis neural network (RBF) was developed. The performance of RBF was compared with other types of transfer function governed on neurons of neural network. The results showed that the DCM with horizontal separated boundary among the subsections with correlation of determination (R2 = 0.76) is accurate through the analytical approaches. Assessing the results of the MLP model showed that this model with (R2 = 0.95) is a bit more accurate than the RBF (R2 = 0.85) and analytical approaches.

Dam-break characteristics of landslide dams with different types of open channel discharge sections

The excavation of artificial open channels in landslide dams is one efficient method for reducing the risks of landslide lake formation. This method has often been used in emergencies to eliminate landslide lakes in earthquake-prone areas of Wenchuan, China. In this study, the dam-break characteristics of landslide dams with different open channel cross sections and longitudinal sections were evaluated. The degree of headward erosion was extremely strong in the natural dam-break experiment and moderately strong in the compound-section dam-break experiment. The degree of headward erosion in the open channel with the trapezoidal section was comparatively mild. Furthermore, the natural dam break resulted in large peak discharge and short dam-break duration. By contrast, the artificially opened channel dam breaks resulted in peak discharges that were approximately 7.7-20.1 % lower than those of natural dam breaks, and the dam-break duration (i.e., the time until the dam broke) was longer than that of the natural dam breaking. The channels with gentle-steep slopes or alternating gentle-steep slopes resulted in greater discharge rates, and a significant amount of erosion occurred due to these open channels. The degree of headward erosion in the channel with alternating gentle-steep slopes was greater than that in the other channels. The peak discharges of the open channels with gentle-steep slopes or alternating mild-steep slopes were approximately 29.6-65.0 % greater than those of the open channel with a linear section. A channel with a triangular cross section and a linear longitudinal section should be used to dispose of small landslide lakes. However, channels with compound cross sections and longitudinal sections with alternating slopes should be used for large or medium landslide lakes.

Weir velocity formulation for sharp-crested rectangular weirs

Discharge in open channels can be measured by sharp-crested rectangular weirs. Generally, measured head over the weir crest is substituted into an empirical formula derived from energy considerations to calculate the discharge. Assumptions made on the derivation are taken into account by defining a discharge coefficient that fits into the experimental data. In this study, a physical quantity, the average velocity over the weir section defined as ‘weir velocity’ is directly formulated as function of weir geometry and head over the weir. Weir velocity plotted against the weir head has a universal behavior for constant weir width to channel width ratio independent of the weir size. This unique behavior is described in terms of weir parameters to calculate the discharge without involving a discharge coefficient. Combining weir velocity data for variable weir widths provides a basis for direct formulation of discharge. The weir velocity exhibits simpler functional dependency on weir parameters in contrast to the discharge coefficient.

Co-efficient of discharge variation for different semi-circular weirs

Critical flow in control sections prevents the downstream water level and flow conditions from affecting the flow through the critical sections, and the discharge can be computed as a function of the measured upstream head. Measurements of irrigation water flows in field channels have usually been expensive, too often of questionable accuracy and otherwise difficult to apply to all field situations. The techniques available in open channel hygrometry are the use of hydraulic structures (devices), velocity-area methods, dilution techniques and slope-hydraulic radius and area methods. Considering the constraints in the measurements of low discharges in open channels, hydraulic structure technique is best suited. Crest height had been increased from 10 cm to 25 cm then the Cd values also decreased from 0.82 to 0.50 for discharge decreased from 24 to 6 Ls-1 under free flow conditions. The co-efficient of discharge for the different weirs under 60 per cent submergence conditions, if the increased crest height was from 10 cm to 25 cm then the Cd values also decreased from 0.75 to 0.43 for 24 to 6 Ls-1 discharge. Under 75 per cent submergence conditions, if the increased crest height was from 10 cm to 25 cm then the Cd values also decreased from 0.7 to 0.42 for discharge decreased from 24 to 6 Ls-1. Under 90 per cent submergence conditions, if the increased crest height was from 10 cm to 25 cm then the Cd values also decreased from 0.69 to 0.42 for 24 to 6 Ls-1 discharge. For 24 Ls-1 discharge, the co-efficient of discharge has been decreased from 0.72 to 0.62 for increased submergence levels from 60 per cent to 90 per cent due to increase in contact surface area and friction and less discharge have low velocity of approach.