Open Channel Flow Measurement Research Articles

Analysis and numerical simulation of different flowmeters based on an open channel in an irrigation area

ABSTRACT This study establishes an ultrasonic open channel flow measurement test and numerical simulation model and systematically compares the performance and reliability of the ultrasonic method and the traditional flowmeter in flow measurement in the irrigation area by observing and analysing the test data and combining it with the numerical simulation. In the indoor ultrasonic flowmeter flow measurement experiments in the trapezoidal nullah section, the flow rate measurement was carried out by using a high-precision variable slope flume and a variety of flow measurement tools. A numerical study was carried out using the VOF method to calculate the flow in the open channel flume under two-phase flow conditions. Combining experimental measurements and numerical simulations, this study aims to quantify the magnitude of flow measurement errors and water surface fluctuations in open channel flumes and to address the discrepancies between different flow measurement methods in open channels in irrigation areas.

Review of hydraulic performance of open‐channel flow‐measuring flumes

The review explored various flumes used for open channel flow measurement and provided insight into operational concepts, discharge measurement, range of flow, head loss requirements, degree of accuracy and submergence, advantages, and limitations for use. The reviewed flumes included; Parshall flumes, Montana flumes, Cutthroat flumes, H-flumes, Trapezoidal flumes, Replogle-Bos-Clemmens (RBC) flumes, Palmer-Bowlus flumes and Central Baffle flumes (CBF). Based on the stage and discharge relationship, the reviewed flumes have a reasonable accuracy of ± 10 % over a wide range of flows. RBC flumes are the most accurate flumes (± 2 %). For flows that deal with a lot of sediments, most flumes have self-cleaning capability except for Palmer-Bowlus flumes and Central Baffle flumes. H-flumes have low resistance to submergence. The submergence transition for H-flumes is only 25-30 %. RBC flumes and Palmer-Bowlus flumes have the highest submergence (90 %). CBF and Palmer-Bowlus flumes need to be improved in order to have self-cleaning capability. Submerged flow corrections need to be developed and published for Palmer-Bowlus flumes and RBC flumes. The reviewed flumes effectively operate with a minimal head loss. The review has provided an insight on selection of an appropriate type of flume for flow measurement in open channels.

A Study on the Measurement Characteristics of the Spring-Plate Flow Measurement Device

In order to improve the effective utilization of agricultural irrigation water and to reasonably allocate water resources in irrigation areas, it is necessary to use open channel flow measurement devices that are accurate and easy to carry. In this study, a spring-plate flow measurement device with different plate widths was designed. Through a combination of theoretical analysis and numerical simulation, the measurement characteristics of the device in specific channels under conditions of 20–105 m3/h flow were studied, the relationship between the flow rate and the force acting on the plate surface was fitted, and the hydraulic characteristics of water flow during its use, such as pressure, velocity distribution, and head loss, were analyzed. The results show that in the process of using the spring-plate flow measurement device, the force on the plate surface increases with the increase in the flow rate, and the force on the plate surface is related to the flow rate in the channel by a power of 5/6. The width of the measurement plate impacts the accuracy of flow measurement, and the smaller the plate width, the larger the error in flow measurement. The distribution of pressure on the measurement plate is similar to that of static pressure, and the pressure increases with the increase in the width of the measurement plate. The upstream flow velocity of the device is small, and the water level increases due to obstruction of the measurement plate. When it connects to the downstream water surface, the water level rapidly decreases, and the flow velocity increases. In using the spring-plate flow measurement device to measure flow, head loss will be produced, and the magnitude of this loss increases with the increase in the width of the measurement plate. The research results provide a theoretical basis for the application of spring plate flow-measuring devices in irrigation areas.

Flow measurement in open channels using imaging techniques in conjunction with a convolutional neural network

Data related to river velocity and discharge are important for water resource management. Non-intrusive image measurement techniques based on direct cross-correlation (DCC) algorithms, such as particle image velocimetry (PIV), are widely used to measure velocity and discharge in the field. However, environmental noise is highly complex and uncontrollable in the field, significantly reducing the accuracy of DCC-based methods. Convolutional neural networks (CNNs) are commonly used in image recognition because of their outstanding accuracy, which far exceeds that of conventional imaging methods. However, these accuracy levels cannot be directly extrapolated for flow movement estimation. Therefore, in this study, we developed an innovative sub-pixel correction technique that allows CNN-based methods to obtain stable measurements in the PIV framework. This is the first study that successfully applied the concept of CNN to measure velocity data using images. The Hamel-Oseen vortex-flow, uniform steady-flow, and plane laminar jet-flow models are established as benchmark vector fields. Non-uniform illumination and Gaussian noise with varying degrees of interference are added to the synthetic data to evaluate the performance of the CNN-based method in PIV. For noiseless images, the DCC-based and CNN-based methods achieve lower measurement errors than benchmark errors. For noisy images, the DCC suffers a fold error increase ranging from 2.77 to 31.13, whereas the CNN suffers only a fold error increase ranging from 1.25 to 1.68. A 30-m-long flume is then used in an uncontrolled environment to mimic real-world flow measurement. The dispersion of the instantaneous velocity measurements for the CNN is more concentrated than that for the DCC. The acoustic Doppler velocimetry yields an error of only 7.87% in discharge estimation using CNN. These results indicate that the CNN-based method is more robust than conventional methods and has the potential to be effectively applied to measurements in the field.

Assessment of a Smartphone App for Open Channel Flow Measurement in Data Scarce Irrigation Schemes

Accurate water flow measurement ensures proper irrigation water management by allocating the desired amount of water to the irrigation fields. The present study evaluated whether the non-intrusive smartphone application “DischargeApp” could be applicable and precise to measure small canal flow rates in the Koga irrigation Scheme. The app was tested in unlined canals with flow rates ranging from 15 to 65 l/s using a 90° V-notch weir. The app is found to overestimate high flow rates. Another source of uncertainty is that the app employed a constant surface velocity conversion factor (C = 0.8) to compute discharge. The accuracy was enhanced by recalculating the measured discharge using a new surface velocity conversion factor that depends on depths. The new conversion factor decreased the errors of MAE and RMSE by 47% and 52%, respectively. Where channel and other optional measuring techniques are not available without interfering with the flow operation conditions in place, the DischargeApp devices can be used to measure flows. The DischargeApp could be used to collect data using local citizens in data-scarce areas. This study suggested reconfiguring the DischargeApp with a new surface velocity conversion coefficient based on flow depths in field conditions for better performance.

Subgrid Variational Optimized Optical Flow Estimation Algorithm for Image Velocimetry

The variational optical flow model is used in this work to investigate a subgrid-scale optimization approach for modeling complex fluid flows in image sequences and estimating their two-dimensional velocity fields. To solve the problem of lack of sub-grid small-scale structure information in variational optical flow estimation, we combine the motion laws of incompressible fluids. Introducing the idea of large eddy simulation, the instantaneous motion can be decomposed into large-scale motion and a small-scale turbulence in the data term. The Smagorinsky model is used to model and solve the small-scale turbulence. The improved subgrid scale Horn-Schunck (SGS-HS) optical flow algorithm provides better results in velocity field estimation of turbulent image sequences than the traditional Farneback dense optical flow algorithm. To make the SGS-HS algorithm equally competent for the open channel flow measurement task, a velocity gradient constraint is chosen for the canonical term of the model, which is used to improve the accuracy of the SGS-HS algorithm in velocimetric experiments in the case of the relatively uniform flow direction of the open channel flow field. The experimental results show that our algorithm has better performance in open channel velocimetry compared with the conventional algorithm.

Stage-Discharge Relationships of Broad Crested Weir for submerged Flow Condition Utilizing Incomplete Self-Similarity(ISS) Technique

Abstract A broad-crested weir is one of the simplest and oldest hydraulic structures.It was used to measure flow regulate flow depth and control flood passage. Open channel flow measurement requirements are based on the experiments performed to evaluate the empirical discharge coefficients and equations. The aim of this study is to develop the stage-discharge relationships using incomplete self-similarity theory and traditional methods for calculating the discharge coefficient (Cds) and to determine which method is the most effective. All experiments were carried out in a channel with a cross-section of (0.5 × 0.5) m and a length of 15 m. 125 experiments were carried out on 25 physical models of a broad crested weir with a rounded edge, under submerged flow conditions. The results showed, after comparing the two methods, and by calculating the mean absolute relative error (MARE) for discharges . It is equal to (4.25%) using the incomplete self-similarity theory, and it is equal to (7.05) by using the traditional method. Thus, the incomplete self-similarity formula is more accurate than the other method.

Determination of the General Formula to Estimate the Discharge Quantity of Composite Structure for Free Flow

River and open channel flow measurement is regarded as an important element in improving water system management. An experimental analysis in a laboratory flume has been executed to obtain formulas which can be used to predict the discharge quantity which crosses over the sharp crested weir and under the gate in the composite structure which is a tool of flow measurement. These formulas are applied for the free flow condition. Different configurations of composite structure have been used. These configurations have regular and irregular shapes. The derivation of the discharge quantity equation is based on the dimensional analysis which is employed to analyze the factors that control the operation of the composite structure. The family of formulas consists of eight formulas that are divided into two groups. The first group consists of four formulas which are derived based on the variable that dominates the hydraulic behavior of the composite structure, while the second group consists of four formulas based on the same variables of the first group but taking into consideration the effect of weir and gate shape by adopting the hydraulic radius of weir and gate. Based on the evaluation process, all formulas can be used perfectly well to predict the discharge quantity, regardless of the shape of weir and gate. On the other hand, based on the validation process, the formula that considered the effects of shape geometry, flow and fluid properties has given the best prediction of the discharge quantity.

Iot Sensor Integration and Calibration for Open Channel Flow Measurement

Iot Sensor Integration and Calibration for Open Channel Flow Measurement

Discussion of “Cylindrical Central Baffle Flume for Flow Measurement in Open Channels” By Aniruddha D. Ghare, Ankur Kapoor, and Avinash M. Badar

Discussion of “Cylindrical Central Baffle Flume for Flow Measurement in Open Channels” By Aniruddha D. Ghare, Ankur Kapoor, and Avinash M. Badar

Discussion of “Cylindrical Central Baffle Flume for Flow Measurement in Open Channels” By Aniruddha D. Ghare, Ankur Kapoor, and Avinash M. Badar

Discussion of “Cylindrical Central Baffle Flume for Flow Measurement in Open Channels” By Aniruddha D. Ghare, Ankur Kapoor, and Avinash M. Badar

Discussion of “Cylindrical Central Baffle Flume for Flow Measurement in Open Channels” By Aniruddha D. Ghare, Ankur Kapoor, and Avinash M. Badar

Discussion of “Cylindrical Central Baffle Flume for Flow Measurement in Open Channels” By Aniruddha D. Ghare, Ankur Kapoor, and Avinash M. Badar

Discussion of “Cylindrical Central Baffle Flume for Flow Measurement in Open Channels” by Aniruddha D. Ghare, Ankur Kapoor, and Avinash M. Badar

Discussion of “Cylindrical Central Baffle Flume for Flow Measurement in Open Channels” by Aniruddha D. Ghare, Ankur Kapoor, and Avinash M. Badar

Closure to “Cylindrical Central Baffle Flume for Flow Measurement in Open Channels” By Aniruddha D. Ghare, Ankur Kapoor, and Avinash M. Badar

Closure to “Cylindrical Central Baffle Flume for Flow Measurement in Open Channels” By Aniruddha D. Ghare, Ankur Kapoor, and Avinash M. Badar

Experimental and theoretical modeling of a quarter-circular gate flow

Gates are important hydraulic structures and used for flow measurement, water delivery, and water level regulation in open channels and irrigation networks. In this study, the quarter-circular gate is introduced and investigated. The cross section of this gate consists of a quarter circular arc and the lip angle of the gate equals to zero. Discharge coefficient, variation of downstream flow depth, and velocity distribution at opening section of gate were experimentally measured. Using potential flow theory supported by dimensional analysis, equations for discharge coefficient and velocity distribution at gate opening section of quarter-circular gate were derived and then validated using experimental data. The mean percentage error (MPE) of obtained equation for discharge coefficient of quarter-circular gate was calculated as 2.24%, indicating the high precision of the proposed theory. Based on obtained results, downstream flow depth of quarter-circular gate is uniform. Also, velocity distribution at gate opening section is nearly uniform. Discharge coefficient of quarter-circular gate was averagely obtained 55% larger than that of sluice gate. It was also obtained larger than that of radial gate. Elimination of contraction section at downstream of gate opening, which is the main source for energy loss and therefore discharge capacity reduction, is the main reason for larger discharge coefficient of quarter-circular gate.

Flow Measurements in Open Channels Using Integrating-Floats

The flow measurements have increased importance in the last decades due to the shortage of water resources resulting from climate changes that request high control of the available water needed for different uses. The classical technique of open channel flow measurement by the integrating-float method was needed for measuring flow in different locations when there were no available modern devices for different reasons, such as the cost of devices. So, the use of classical techniques was taken place to solve the problem. The present study examines the integrating float method and defines the parameters affecting the acceleration of floating spheres in flowing water that was analyzed using experimental measurements. The method was investigated theoretically, as well as many experimental tests in a fixed floor laboratory flume were conducted. Different sizes of solid plastic spheres with different weights were used as floats to measure velocities and then discharge computation. The results indicate that the integrating-float technique is feasible and accurate for measuring low flow velocity in open channels. It was desirable to use small floats with specific gravity closer to unity to get more accurate results. The measured velocities and the estimated discharges were compared with discharges obtained using some other common laboratory measuring techniques. Good agreement was obtained between the integrating-float method results with the results of velocities obtained using other measurement techniques, with an error of less than 2.5%.

Flow Measurements in Open Channels Using Integrating-Floats

The flow measurements have increased importance in the last decades due to the shortage of water resources resulting from climate changes that request high control of the available water needed for different uses. The classical technique of open channel flow measurement by the integrating-float method was needed for measuring flow in different locations when there were no available modern devices for different reasons, such as the cost of devices. So, the use of classical techniques was taken place to solve the problem. The present study examines the integrating float method and defines the parameters affecting the acceleration of floating spheres in flowing water that was analyzed using experimental measurements. The method was investigated theoretically, as well as many experimental tests in a fixed floor laboratory flume were conducted. Different sizes of solid plastic spheres with different weights were used as floats to measure velocities and then discharge computation. The results indicate that the integrating-float technique is feasible and accurate for measuring low flow velocity in open channels. It was desirable to use small floats with specific gravity closer to unity to get more accurate results. The measured velocities and the estimated discharges were compared with discharges obtained using some other common laboratory measuring techniques. Good agreement was obtained between the integrating-float method results with the results of velocities obtained using other measurement techniques, with an error of less than 2.5%.

Discharge performance of plan view of multi-cycle W-form and circular arc labyrinth weir using machine learning

Weirs serve the dual purpose of flow measurement and flow regulation in open channels. In the past, weirs of improved plan form have been used to increase the discharge through the weir and to regulate the afflux. This study presents the results of the experiments that were carried out to investigate the discharge capacity of a multi-cycle W-form labyrinth weir and a sharp-crested circular arc weir. The experiments were performed in a rectangular flume under free-flow conditions. For the labyrinth weir, observations were recorded corresponding to five cycles while varying the weir height from 5 cm to 30 cm in steps of 5 cm. For the circular arc crested weir, the arc length was changed by considering five different values of the apex angle, and the crest height was varied from 5 cm to 30 cm in steps of 5 cm. The data obtained from the experiments were used for building predictive models using Multiple Linear regression (MLR), Support Vector Machine (SVM) and Artificial Neural network (ANN). In SVM, a regression model was constructed while in the ANN, feed-forward back propagation neural network with multiple perceptron layers was used to predict the discharge. Metrics like average percentage error (APE), Coefficient of Determination (R2) and Coefficient of efficiency (CE) were used for validating the models. From the present study, it was observed that the SVM regression model performed better than the rest of the models.

Discussion on standardization and automatic flow measurement of U-shaped channel water

Abstract: In human life, water resources are inseparable. In recent years, China's population growth has accelerated, and the industrial level has been continuously improved, resulting in the rapid use and waste of water resources. The protection and rational distribution of water resources is the most pressing issue in China's water resources. At present, the water measuring facilities of the U-shaped channel mainly include a straight wall measuring pool, a parabolic throat measuring pool and a long throat measuring pool. In view of the problems in irrigation measurement, the empirical water measurement of basic open channel and automatic flow measurement system in irrigation district is summarized to improve the accuracy, fairness and rationality of water measurement, and promote irrigation district management to a higher level.

Closure “Three Simple Flumes for Flow Measurement in Open Channels” by Zohrab Samani

Closure “Three Simple Flumes for Flow Measurement in Open Channels” by Zohrab Samani