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Sharp-crested weirs are commonly used in hydraulic engineering for flow measurement and control. Despite extensive research on sharp-crested weirs, particularly regarding their discharge coefficients, more information is needed via research on their energy dissipation downstream. This study conducted experimental tests to assess the influence of contraction ratio (b/B) of rectangular sharp-crested weirs (RSCWs) on energy dissipation downstream under free flow conditions. Five RSCWs with different b/B equals 6/24, 7/24, 8/24, 9/24, and 10/24 were used. The results showed a consistent decrease in relative energy dissipation (ΔEr) with an increase in the head over the weir. Furthermore, as the discharge per unit width (q) increased, the relative energy dissipation (ΔEr) decreased, indicating more efficient discharge over the weir. A higher b/B further reduces ΔEr, suggesting that wider weirs are more effective in minimizing energy losses. The maximum relative residual energy (E1/E0) and relative energy dissipation (ΔEr) occurred at b/B = 10/24 and 6/24, with values of 0.825 and 0.613, respectively. Additionally, the maximum discharge coefficient (Cd) of RSCWs is found at b/B = 6/24, with an average value of 0.623. The results support the accuracy of the proposed equation with R2 = 0.988, RMSE = 0.0083, and MAPE = 1.43%. [ABSTRACT FROM AUTHOR]

A rectangular slit weir is used to measure small flows, namely, those flows less than 5 L/s and contraction ratios (b/B) less than 0.25. In the present study, flow tests were conducted in a laboratory setup with various contraction ratios (b/B) under models A (b/B = 1/12), B (b/B = 1/8), C (b/B = 1/6), D (b/B = 5/24), and E (b/B = 1/4). The dimensional analysis revealed that b/B, the height of the flow on the crest of the weir to the height of the weir crest (h/P), the Reynolds number (Re), and the Weber number (We) are effective parameters for predicting the discharge coefficient of the slit weir. The experimental results indicated that the discharge coefficient is variable for different contraction ratios; the maximum average discharge coefficient was achieved at the lowest b/B (Model A), with a value of 0.72. The minimum average discharge coefficient obtained in Model B equals 0.639. In addition, former prediction equations were compared with the obtained experimental data, and the minimum, average, and maximum errors were calculated. Furthermore, a relationship was established for deriving the discharge coefficient in slit weirs with R2 = 0.9212, RMSE = 0.02244, and MAE = 0.0134 based on the obtained experimental data with four effective parameters, b/B, h/P, Re, and We. [ABSTRACT FROM AUTHOR]

A large collection of laboratory measurements of piezometric head (h) and discharge (Q) were made over hydraulic models of a tilting weir at nine different angles, ranging from 25.7° to 90° within a 0.3-m-wide flume. These measurements were corroborated with additional laboratory data taken within a 1-m-wide flume across four inclination angles. The range of both inclination angle (θ) and flow scale examined in this study elucidate the nature of the head-discharge rating equation beyond previous work. Results show that as θ decreases under a constant Q , the h over the weir decreases in a monotonic fashion due to the shallower angle of attack of the flow, which results in less curvature of the streamlines over the crest and therefore less deviation from the upstream hydrostatic pressure condition. To incorporate this effect into the head-discharge rating equation, a transformation of the h term was applied by multiplying the measured h that occurs over a tilting weir by a correction factor to match the effective h that would occur if the weir were aligned perpendicular to the flow at the same discharge. Thus, a modified form of the classical sharp-crested weir rating equation can be used as a means for determining the value of Q for tilting cases to a high degree of accuracy. The degree of accuracy is dependent on dimensionless Reynolds and Weber numbers describing the flow inertia in the approach to the weir in relation to respective viscous and surface tension scale effects. This approach portends marked flow measurement enhancement for flow conditions above a suggested inertial threshold. To achieve reliable and equitable water distribution, it is necessary to accurately estimate the volumetric discharge of water to flow through "rivers and canals." One such method of accomplishing this is by using hydraulic structures, such as the tilting weir. This structure not only can be used to measure the discharge of water on a continuous basis, but also allows for regulating the water level upstream of the structure. Presently, tilting weirs are often used to control water levels, but the literature on their utilization as flow measurement structures has remained sparse. This study presents a thorough analysis of laboratory experiments on scaled models of tilting weirs, where the flow depth upstream of the structure and the inclination angle are used to calibrate an equation to estimate the discharge to a high degree of accuracy. Operational guidelines to ensure minimum uncertainty in measurement are also given. [ABSTRACT FROM AUTHOR]

Please insert a Abstract as per journal style: This discussion paper is regarding the values of coefficient of discharge (Cd) and submergence (S) of a vertical type of sluice gate mounted on a broad casted weir. Discusser has used open channel specific energy principles justifying the values of Cd found by the author theoretically. Discusser has furnished the experimental values of Cd for a vertical type and tainter type gates. Discusser has also added the experimental values of Cd under free and submerged flow conditions in a model study for Salal dam spillway. An innovative proportional type flow meter developed by the discusser has been furnished for flow measurement within a given flow range. [ABSTRACT FROM AUTHOR]

Please insert a Abstract as per journal style: This discussion paper is regarding the values of coefficient of discharge (Cd) and submergence (S) of a vertical type of sluice gate mounted on a broad casted weir. Discusser has used open channel specific energy principles justifying the values of Cd found by the author theoretically. Discusser has furnished the experimental values of Cd for a vertical type and tainter type gates. Discusser has also added the experimental values of Cd under free and submerged flow conditions in a model study for Salal dam spillway. An innovative proportional type flow meter developed by the discusser has been furnished for flow measurement within a given flow range. [ABSTRACT FROM AUTHOR]

Triangular sharp-crested weirs are commonly used to measure low-flow measurements in open channels. The flow over such a V-notch is proportional to the height of water above the weir on the upstream side. Therefore, it is relatively easy to calculate the flow from standard equations by using only recordings of water levels. Thus, these types of weirs can provide inexpensive measurements of flow volumes and resulting nutrient loads from subsurface drainage systems and associated conservation practices. The objective of this study was to develop appropriate weir equations for a 22.5° V-notch weir developed for a new tubular water level control structure in a controlled drainage system (CD). Analyses using this weir, with three typical slope angles of 30°, 45°, and 60°, were also conducted. There were no significant differences in the fitted parameters across the three analyzed slope angles. The coefficient of determination (R2) values were 0.9955, 0.9981, and 0.9980, respectively. However, the best-fitted equation for a 22.5° V-notch weir was for a slope angle of 45°. The flow equation was Q = 0.2235H2.4182, with Q in liters per minute and H in centimeters. This equation can be used for measuring flow through tubular-controlled drainage structures. [ABSTRACT FROM AUTHOR]

This paper describes the hydraulic characteristics of flow through a sluice gate over a broad-crested weir with a fixed upstream ramp slope of 1:2 and downstream ramp slopes of 1:2, 1:3, and 1:4. A relationship was proposed to determine the contraction coefficient of the flow passing through the gate, under free-flow conditions, in which the average value was 0.71 for all observed data. The developed relationship was used to calculate the head-loss coefficient from the studied structures under free-flow conditions, which averaged 0.31. The value of the mean absolute relative error for the proposed relationship to estimate the discharge coefficient under free-flow conditions was 1.7%. Examination of the different downstream slopes on the discharge coefficient under free-flow conditions showed that a downstream ramp slope of 1:3 is most appropriate when compared to the results for the other slopes. The value of the mean absolute relative error of the developed relationship to estimate the discharge coefficient under submerged flow conditions was 5.7%, while its corresponding value from the WinGate software was 13.1%. A survey of the effect of downstream ramp slope on the depth of submergence threshold showed that an increase in the downstream slope tends to increase the depth of the submergence threshold, whereby its value under low slopes was not significant. [ABSTRACT FROM AUTHOR]

Trapezoidal profiled weirs and barrages are employed extensively in agrarian countries like India and Pakistan for diverting river water for canal-fed irrigation. The downstream slope of a weir is designed as 1V∶3H , although in some older structures, slopes as mild as 1V∶5H are noticed. Downstream slopes of 1V∶5H also exist for the barrages on the Nile in Egypt and in the standard Crump weir used in the UK and some European countries. This study explores the effect of the downstream slope of a short-crested trapezoidal weir on its flow hydraulics and conveyance properties. Irrigation barrages and weirs, apart from diverting water to a canal, also help in measuring the discharge of a river, which is a function of the up- and downstream water levels. For large discharges during floods, the gates of a barrage are withdrawn to ensure an uncontrolled flow that may either be free or submerged, depending on the downstream water level. Although past studies on uncontrolled flows have recognized the effect of the upstream slope of a weir on the coefficient of discharge, Cd , this study establishes that it is also influenced by a weir's downstream slope. An equation of Cd for free flows and a flow reduction factor for submerged flows are proposed considering both weir-face angles. For free flows, Cd is seen to increase with the steepness of a weir's downstream slope; for submerged flows, the discharge reduction factor is observed to improve as the slope becomes milder, leading to a greater conveyance. Data from our own laboratory experiments, past publications, and results derived from a 2D RANS-VOF multiphase computational fluid dynamics model are used in arriving at the conclusions reported in the study. [ABSTRACT FROM AUTHOR]

Copyright of Advances in Water Science / Shuikexue Jinzhan is the property of Editorial Board of Advances in Water Science and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

[Objective] Flow measurement through sluice gates in U-Shaped channels depends on a range of factors. We experimentally measured the characteristics of flow through the gates under different designs and working conditions, and then derived a formula using these data to estimate flow rates based on hydraulic characteristics of the gate and channel, as well as the working conditions. [Method] The experiments were conducted by controlling the flow rates from 10 to 50 L/s. The critical ratio of orifice flow to weir flow, as well as the flow capacity were analyzed utilizing hydraulic parameters, including water surface line, Froude number, and water head loss across the gate. These parameters were used in the orifice flow formula to calculate the flow rate. [Result] The critical ratio of orifice flow to weir flow was close to 1, the Froude number was uniformly distributed along the flow path, and the average relative head loss across the gate was 7%. Compared to the measured data, the error of the derived formula was less than 3.5%. [Conclusion] The sluice gate for the U-Shaped channel works well, and water head loss across it is minor. The derived formula for calculating flow rate is accurate. These results are helpful for designing U-shaped channels in irrigation areas and calculating flow rates through them. [ABSTRACT FROM AUTHOR]

The weir height was HT ht and HT ht was 0.02 m thick as shown in Fig. Discharge Formulas and Discharge Coefficients The flow regimes (as a function of HT ht for HT ht ) are compared in Fig. The elevation head over the weir crest, HT ht , was varied between 0.05 and 0.25 m. If HT ht is too low to form free flow, then clinging flow occurs, such that those HT ht formulas are not applicable. [Extracted from the article]

Subcritical flows over highway and railway embankments, commonly encountered during flood events, can be treated like submerged flows over trapezoidal-shaped weirs. In earlier studies, the equation of the submerged-flow discharge for such types of weirs was developed as a function of the degree of submergence and free-flow discharge. However, the application of this equation in practice requires a pre-determined discharge from experiments performed under free-flowconditions. In this study, a discharge equation was deduced from the streamwise momentum balance equation, which overcomes the drawback of the previous approaches. The results of the validation demonstrated that the proposed equation is capable of predicting the submerged-flow discharge of a trapezoidal-shaped weir within ±6.0% of the measured value. Furthermore, the most prominent features of the submerged overflows were examined by systematically analyzing the experimental data. For such flows, the free-surface and bed-pressure profiles are self-similar only over the upstream face of the weir. Results of this investigation confirmed that the degree of submergence and the slope of the downstream weir face significantly affect the characteristics of the submerged flow, but the effect of the latter on the non-modular discharge is marginal. [ABSTRACT FROM AUTHOR]

Due to its horizontal crest in the transverse direction and its inclined upstream and downstream faces, whose inclination is well defined, the Crump weir can be classified into the category of triangular longitudinal profile weirs, including the Bazin weir. It is an intermediate category between that which includes thin-crested weirs characterized by reduced thickness and that which includes broad-crested weirs that extend over a given length in the streamwise direction. In practice, the Crump weir is preferably used as a sill for several reasons. The weir reduces the upstream flow velocity by raising the water level, which reduces or even avoids erosion. Additionally, the measurement of the upstream flow depth h, counted above the weir, is carried out with the greatest precision when the device is used as a flow meter. The Crump weir as a flow measuring structure has not been studied from a theoretical point of view, and only experimental observations have enabled it to be calibrated. The resulting stage-discharge relationship is not only empirical but also incomplete since the effect of influential parameters, such as h/B, where B is the width of the rectangular approach channel, has not been accounted for, which affects the accuracy of the flow rate calculation. Only the effect of the relative elevation of the crest weir P* = P/h on the flow rate was examined on the basis of observations, where P is the elevation of the crest weir. The dimensionless parameter P* reflects the influence of the vertical contraction of the flow caused by the weir. In this study, it is proven that the ratio h/B accounts for 23.5% as an average effect in the calculation of the discharge coefficient Cd and hence of the flow rate Q. The refined model describing this effect is yielded based on the analysis of observations available in the literature because current theories are unable to produce a mathematical representation of this effect. Unlike h/B, the effect of P* is derived from a rigorous theory based on the energy equation, judiciously transformed into dimensionless terms, along with rational hydraulic concepts. Therefore, the discharge coefficient relationship resulting from this study is a semiempirical formula that can be written symbolically in the following form Cd = αf1(h/B)f2(P*). It is inferred that α is a constant whose appropriate value is estimated to be 0.8601, while the symbolic functions f1 and f2 are explicitly defined as simple and handy relationships. Compared to recent observations, the previous Cd relationship causes a maximum deviation of only 0.864%, resulting in the same maximum deviation in the flow rate Q computation. Therefore, it can be considered the most accurate and comprehensive Cd relationship ever developed before for the Crump weir working under free overflow conditions. This allows the user to estimate the rate Q sought with great certainty and confidence. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Irrigation & Drainage is the property of Journal of Irrigation & Drainage Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The hydraulic relationships of flow through the weir of different common shapes were investigated in this study. The hydraulic performances of weirs were carried out experimentally, by using eight different types of weir models, and the effect of various shapes of the weir to specify different hydraulic parameters such as coefficient of discharge (Cd), weir geometric shape and size constants (K) and weir shape number (n), energy dissipation ratio (E %) for selecting best flow measuring weir type. The experimental work was carried out on a tilted rectangular flume with 7.5 m long, 0.30 m wide and 0.45 m deep with a discharge range 0.50–20.95 L/s. The experimental results of this study showed that the dissipation energy corresponding to triangular notches is larger than the resulted from rectangular notches. For compound notches of rectangle and triangle, turbulence inflow increases as the angle of lower notch decreases. Thus, this type with an angle of (θ = 120ο) is the most efficient between the studied models, which gives the average Cd of 0.82, the value of K is equal to 0.75 and n values of 1.96, and the dissipation of flow energy ratio of (35.86%) for strong hydraulic jump. Finally, depending on a statistical basis, this study derived empirical relationships to estimate the coefficient of discharge with acceptable values of the coefficient of determination. [ABSTRACT FROM AUTHOR]

This study reexamines flow over a sharp-crested weir using computational fluid dynamics (CFD) to identify the optimal operating range under which the weir functions with accuracy as a free-flowing measurement device. A numerical parametric study was conducted for two separate channel and weir geometries under a range of flow rates resulting in different h/P values, where h is the elevation head over the weir crest, and P is the weir height. Analysis of velocity and pressure profiles over the weir revealed three distinct flow regimes: a high acceleration regime, an ideal operating regime, and a weir-inundated regime that may lead to submerged flow. The high acceleration regime correlates to flows with h/P<0.6 , and the weir-inundated regime occurred when h/P>2.0. The ideal operating regime was found to occur in the range 0.6

Weirs are structures that are important for measuring flow and controlling water levels. Research has shown that the discharge coefficient is not constant and depends on the crest length, the height of the weir, the upstream head, and the upstream and downstream slopes. In this study, the effect of these parameters on the discharge coefficient (Cd) is investigated by numerical simulation. The current study present numerical simulation using the ANSYS FLUENT software. The total number of simulations is 432 which includes: 4 upstream slopes, 4 downstream slopes, 3 weir heights, 3 upstream heads (h1) and 3 weir crest lengths. It was found that the downstream face slope has little effect on Cd. For 0.1 < H1/w < 0.4 by decreasing the upstream slope, Cd increases, where H1 is the water head on the weir crest and w is the length of the crest. Also, for the same range, by decreasing the height of the weir (p), the Cd increases. For 0.16 < H1/p < 2, as the length of the crest decreases, the Cd increases. By comparing the numerical simulation results to physical measurements, multi-variable regression equations for estimating Cd are presented. In addition to Cd, extraction of other more detailed information such as water level profiles and velocity profiles at different locations is provided. [ABSTRACT FROM AUTHOR]

The article looked at the possibility of making use of a triangular broad crested device, provided with a crest height P and a constant apex angle, as a flow measurement weir. The device has a triangular gorge which extends over a certain length L. This must be sufficient to allow the creation of a control section in a given section of the gorge, which represents the prerequisite condition for the proper functioning of the device. Inserted in a rectangular channel of width B for which the measurement of the flow rate Q is needed, the device causes a lateral contraction of the cross section located above the crest height P. It is shown that the dimensionless parameter M1 = mh1 / B reflects the effect of this lateral contraction, where) 2 / (tg m=, and 1h is the upstream flow depth counted above the crest. Due to the crest height P, the flow also undergoes vertical contraction. The effect of both lateral and vertical contractions can be grouped together in a single dimensionless parameter noted? such that/(1) =M1 + P where 1 P = P/h denotes the relative crest height. After the detailed description of the device as well as the resulting flow, a dimensional analysis has been proposed in order to identify the parameters on which the discharge coefficient d C of the device depends. It has been clearly demonstrated that the flow coefficient can be written as a function of both 1 M1 and *P, i.e.), (P* Cd =? M1 P. In order to define the function, a theoretical approach is proposed based on the momentum theorem and the energy equation. This approach turned out to be judicious since it led to expressing the theoretical relationship that governs the discharge coefficient Cd This was presented as an explicit function of the dimensionless parameter ?, depending therefore on both M1 and P* as predicted by dimensional analysis. After that, experimental tests were rigorously carried out on six devices with different geometric characteristics. The objective was to verify the validity of the theoretical relationship governing the discharge coefficient. The tests were carried out under suitable hydraulic conditions and the flow rate Q and the upstream depth h1 were measured using high precision instruments. In total, 122 measurement points were collected and were carefully analyzed. The use of linear least-squares fitting method involving experimental and theoretical data gave the following trend line relationship: Cd,Exp = 0.9999 Cd,Th = Cd,Th It was thus concluded that the theoretical discharge coefficient relationship did not need any correction and it could be used with great confidence since the maximum deviation observed rarely reached 0.2%. This is also the case for the relationship that governs the flow rate Q. [ABSTRACT FROM AUTHOR]

In this study, the hydraulic features of the SCVW (a novel type of sharp-crested V-notch weirs) were scrutinized in the popular vertex angles θ , i.e., 30°, 45°, 60°, 90°, 120°, 128°, and 150°, under aerated, steady and free overflow conditions in an open channel for large physical models. To assess the changes of the discharge coefficient of the SCVW (i.e., CdSCVW) versus weir height and θ , widespread laboratory works were performed by measuring the water head over the crest of the weir and the discharge. Special formulas for the CdSCVW in the θ=60° were checked, and an appropriate empirical equation was recommended. The calculated CdSCVW by the proposed equation was within 0%–10% of the measured values. Three types of nonparametric artificial intelligence (AI) methods, namely, support vector regression (SVR), gene expression programming (GEP), and a robust hybrid model entitled hybrid (SVR-ACO) were developed to estimate the CdSCVW. For the sake of modeling, 196 experimental datasets were applied in the mentioned methods to evaluate the CdSCVW by taking into consideration the dimensionless variables which impact the determining procedure of the CdSCVW. In this modeling, by varying the architecture and core factors of the aforementioned methods, several scenarios were defined. The generated mathematical equation of CdSCVW by the best scenario of the GEP was compared with the corresponding measured values in which the results were in 0%–10%. According to the attained statistical indices, scatter plots, and the values of the total grade (TG) technique, the hybrid SVR(RBF)-ACO model was determined as the superior and optimal method to estimate the CdSCVW with high performance and accuracy. [ABSTRACT FROM AUTHOR]

Copyright of Larhyss Journal is the property of Biskra University, Research Laboratory in Subterranean & Surface Hydraulics and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The circular crested weir (CCW) has been introduced as weirs having a high discharge coefficient (Cd). The ratio of flow head to the radius of the crest (H/R) is the most important parameter affecting the Cd, that the Cd ≈ a H / R b can mathematical model their relation. In this study, the parameters of the Cd formula (i.e., a and b) were uncertainty analyzed using Monte Carlo (MC) and Bootstrap methods (BM). To perform these methods, some of the built-in functions of Excel software were utilized. The results declared that the average values of a and b were 1.187 and 0.140. The outcome of the MC method showed that the range of a and b at 95% confidence interval changed between 1.179 to 1.194 and 0.134 to 0.146, respectively, while at the same confidence interval the BM ranged from 1.187 to 1.200 and 0.133 to 0.147. [ABSTRACT FROM AUTHOR]

Thus, similar to Wahlin and Replogle's ([3]) recommendation, it is suggested to calculate the discharge over the whole range HT ht , from the free flow formula. In this situation, as HT ht approaches HT ht , the ratio of HT ht is expected to change by about 1. From Eq. (24) and for HT ht , HT ht . [Extracted from the article]

Weirs and orifices of different shapes are widely used as flow-measuring devices or adjusting the upstream water level. These water structures can be combined, yielding a simultaneous flow over the weir and through the gate. A combined weir–gate (weir–orifice) structure can be used for flow measurement with the added benefit that sediment deposition behind the structure will be limited. This study introduces a sharp-edged plate installed at the end of a circular open channel in which flow is discharged into the atmosphere as a simple flow-measurement device. This weir–gate system yields a simultaneously free outflow over and under the plate. Most of the floating materials and sediments will pass through this flow-measurement device because the structure has no lateral contraction. The energy principle (results in weir and orifice relations) helps to deduce a suitable mathematical form for the stage-discharge equation. The energy principle and Buckingham's theorem of dimensional analysis both were used to deduce the stage-discharge relationships. A series of laboratory experiments (626 runs) was conducted in two circular open channels to calibrate the deduced stage-discharge relationships under free-outflow conditions. The results showed that the best model to describe the stage-discharge relationships could be obtained using the energy principle (physically based approach) and dimensional analysis. The proposed general stage-discharge relationship had an average error of 1.89% with a maximum error less than 9.82% for the experimental trials. The results also showed that the dimensional analysis is not powerful enough alone for obtaining an accurate stage-discharge model. The theoretical considerations can make the dimensional analysis powerful enough to obtain an acceptable stage-discharge equation, as shown in this research. [ABSTRACT FROM AUTHOR]

The hydraulic performance of triangular labyrinth weirs with an upstream pool was experimentally studied in both free and submerged flow conditions. The discharge coefficients based on channel width B and the weir length L were calculated from experimental data. It was found that the additional length provided by the pool can significantly increase the capacity of the new weir design. The tested weir models were found efficient and required less concrete in comparison with classical labyrinth weirs for a relatively low head water to weir height ratio of ho/P=0.17. Empirical formulations were developed to predict the discharge coefficient and the critical depth of flow for labyrinth weirs with an upstream pool. The discharge reduction factor ψ of the new weir design was found to be slightly lower than the ψ value of sharp-crested weirs. Performance of the tested weir models in submerged flow condition was directly compared with the sharp-crested weirs. It was found that the submerged flow discharges of the tested weir models were significantly higher than the corresponding submerged flow discharge in sharp-crested weirs. A power law model was proposed to predict the submerged flow discharge from a given water head. The superior performance of labyrinth weirs with an upstream pool over classical labyrinth and sharp-crested weirs in both free and submerged flow conditions make them a suitable choice as a flow measuring device, depth regulator, and flood control structure. [ABSTRACT FROM AUTHOR]

Currently, discharges passing measurement devices and structures in unsteady flow conditions are determined based on relationships developed for steady flow condition due to lack of sufficient data. In this study, the operation of triangular and rectangular sharp-crested weirs in unsteady flow conditions was experimentally investigated. The compiled data indicated the presence of looped rating curves, but with transposition of the rising and falling limbs compared to that commonly observed in stream gauge ratings. The presence of such looped rating curves was justified, and the validity of the steady rating curve relationships, which are presently being applied to unsteady flow conditions, was questioned. Accordingly, relationships for evaluating unsteady discharge passing different rectangular and triangular sharp-crested weirs were presented. The proposed formulas considerably improve the discharge measurements accuracy in unsteady flow conditions and could be incorporated in hydrodynamic models. [ABSTRACT FROM AUTHOR]

The conclusion that practically no sharp-crested weir flow occurs when HT ht is interesting and worthy of further investigation. Data for HT ht , 75°, and 90°, respectively, are provided in Table 1 (see also Fig. We would like to have seen more HT ht values plotted in Fig. [Extracted from the article]

Sharp-crested weirs are frequently used for discharge measurements in open channels. They offer a simple, reliable and accurate flow measurement approach if they are properly installed and maintained. Suppressed weirs can be installed in channels with different shapes. The standard suppressed rectangular weir is well documented in the literature. The current research is conducted to achieve an accurate and simple formula for flow through the suppressed, sharp-crested weir located at the end of circular, open channels. The discharge equation of a suppressed, circular weir ends up as incomplete elliptic integrals of the first and second kinds, which are not very suitable for practical purposes owing to their complexity. In this study, a simple and accurate theoretical discharge equation has been presented for this weir. A series of laboratory experiments (244 runs) are also performed to investigate the discharge coefficient of sharp-crested weirs located at the end of two horizontal, circular, open channels. Using the data collected from two pipes of diameters 19·1 and 30·1 cm, a suitable discharge coefficient equation with an average relative error of less than 2·3% is presented; thus actual discharge through the channel can be simply estimated using the proposed equations. [ABSTRACT FROM AUTHOR]

Traditionally, flow-rating formulas for hydraulic structures are calibrated and validated with data comprising field measurements of discharge, water stages, and operational settings monitored in near real time. Lack of sufficient field measurements that include all flow types and cover the full operational ranges has been a major constraint in developing reliable flow ratings for prototype hydraulic structures. A companion paper introduced a plausible method that relies on computational fluid dynamics (CFD) simulations to generate accurate flow data that complements field measurements for flow rating analysis. In this paper, a general framework for applying CFD in flow rating is proposed, which includes planning of CFD simulations, assessing CFD flow data, and improving existing flow ratings using a hybrid data set of field-measured and CFD-simulated flows. Finally, two case studies of flow rating for spillways and weirs carried out to demonstrate the proposed framework are presented. Results show that the proposed framework offers a cost-effective approach that provides robust, comprehensive flow rating formulas that yield reliable flow estimates for the operation of hydraulic structures under multiple water-resource management constraints. [ABSTRACT FROM AUTHOR]

Pivot weirs are used in irrigation networks to regulate water surface elevation and flow rate measurements. For ease of operation, this type of weir can be implemented in automatic operations of irrigation networks. However, little research has been performed to determine the head-discharge equation for this type of weir. In this research, two equations are used to calculate discharge over the pivot weir. The first equation is Kindsvater-Carter's discharge equation, which is commonly used as the normal rectangular weir equation. The second is derived from energy and critical depth equations. To determine the coefficients of these equations, some tests were performed on an experimental model using three pivot weirs with different angles (θ = 0, 20, 40, 60, 80, and 90°) and side contractions of 0.4, 0.6, and 0.8. The experimental data were then compiled with the United States Bureau of Reclamation (USBR) data, and based on dimensional analysis, the discharge coefficients were estimated for free and submerged flow conditions. The accuracy of two equations under free-flow conditions was within ±15 and ±10%, respectively. The range of error for the second equation in submerged flow condition was less than ±20%, and the submergence factor was between 0.2 and 0.9, which is acceptable for application. [ABSTRACT FROM AUTHOR]

Laboratory experiments were carried out to investigate the water surface characteristics of submerged flow over sharp-crested weirs. Interesting observations were made on the water surface profiles near the weir as weir submergence sets in as well as for various stages of submergence. Submerged flow was divided into four regimes: (I) impinging jet, (II) surface jump, (III) surface wave, and (IV) surface jet. It was found that a surface jump turned into a surface wave when the wave trough became level with the tip of the weir. The surface jet regime began as the surface waves faded out. A condition was set to quantify the boundary between the surface wave and surface jet regimes. Based on flow observations, the surface jet regime sets in as the amplitude of the surface wave becomes small (i.e., less than 0.1h, where h is the head). An empirical equation was developed based on the literature data to predict the discharge reduction factor in the generally used discharge equation. This formulation was compared with other formulations in the literature. It was found that the proposed formulation provides a slightly better estimation of flow discharge. [ABSTRACT FROM AUTHOR]

Weirs and notches are efficient devices for measuring flow rates. Banks of slit weirs forming multislit weirs allow both precise discharge measurements in a very large range of flow rates and permit a good flow regulation. V-shaped weirs are traditionally used as precise laboratory flow measuring devices, especially in the low discharge ranges. In the current investigation, the method of images was used to form the V-shaped multislit weir system to allow measurement and regulation of flows in a large range of flows that includes very low flow rates. Experimental studies were conducted to determine the discharge coefficients of V-shaped multislit weirs over a wide range of weir Reynolds numbers. The study provided a single relation between the weir discharge coefficient and the weir Reynolds number for both the rectangular and V-shaped multislit weir systems. [ABSTRACT FROM AUTHOR]

This paper considers flow measurement in open channels with transverse weirs of finite crest length with sloping crests and upstream or downstream ramps-or both-for free flows. Using the broad-crested weir equation with a discharge coefficient as the basis and following the earlier studies of broad-crested weirs, robust correlations have been developed for the discharge coefficient by using the experimental results available in the literature. Effects of upstream and downstream ramps were studied by introducing the upstream and the downstream length scales, respectively. The proposed correlations of embankment weirs were compared with the head-discharge formulations of embankment weirs in the literature. Triangular (hump) weirs with either upstream or downstream ramps (or both) have also been considered. It was found that in triangular (hump) weirs, the discharge coefficient increases when the downstream slope increases, but it decreases when the upstream slope increases. [ABSTRACT FROM AUTHOR]

A study conducted by the Utah Water Research Laboratory assessed the accuracies of a wide variety of flow measurement devices currently in service. During the study, a wide variety of flow measurement devices, including flumes, weirs, and rated sections in open channel systems, were evaluated; magnetic and ultrasonic meters in closed-conduit systems were also tested. The specified design accuracies for each device are presented. Actual flow measurements were determined at 70 sites and were compared with the theoretical discharges of each device. Comparison of actual and theoretical flow indicates that only 33% of the measurement devices tested currently measure flow within manufacturer-designed specifications. Field data is presented, and possible reasons for the flow measurement errors and their corrections are discussed. [ABSTRACT FROM AUTHOR]

This technical note presents a critical analysis flow over weirs of finite crest length, with square-edged or rounded entrance, for free-flow conditions. Using the flow equation for the broad-crested weir with parallel flow in the critical state as the basis, we have defined the discharge coefficient Cd, with the head on the weir as the length scale. Based on an extensive analysis of the experimental observations in the literature, we have confirmed the classification of finite crest length weirs into four classes of long-crested, broad-crested, short-crested, and sharp-crested weirs. For the square-edged entrance, we have developed robust correlations for Cd when the Weber number is greater than 1. For weirs with a rounded entrance, for which the data set is not that extensive compared to the square-edged case, we have developed good correlations for Cd. [ABSTRACT FROM AUTHOR]

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Laboratory apparatus to simulate flow through culverts has been used to collect discharge and water level measurements. Two different shapes of culvert barrels, namely square and circular, were tested. The measurements presented in this note are intended to provide useful information regarding the variety of flow regimes (including overtopping) through culverts, and the transitions from one flow regime to another. It is known that modeling the culvert flow regimes and capturing the transitions among these regimes numerically is a challenging task. To that effect, the laboratory measurements presented herein can provide a testing and validation data set for numerical modeling of hydraulic structures such as culverts. [ABSTRACT FROM AUTHOR]

Low-head labyrinth weir control structures installed on mild sloping channels or where the channel downstream of the weir is constricting and/or heavily vegetated can experience submergence. Weir submergence occurs when the tailwater surpasses the weir crest elevation, causing an increase in the upstream driving head for a given discharge, relative to a free-discharge condition. The most familiar relationship for predicting submerged weir head-discharge relationships is likely that of James R. Villemonte, which he published in 1947 for sharp-crested linear weirs. For lack of a better alternative, Villemonte’s relation has also been applied to predicting submerged labyrinth weir performance. A new dimensionless submerged head relationship developed in this study is presented for submerged labyrinth weirs. A similar relationship is also presented for linear sharp-crested weirs. The accuracy of the submerged linear weir relationship was equivalent to Villemonte’s and is simpler to solve when working in terms of total upstream head. Relative to Villemonte’s relationship applied to labyrinth weirs, the new submerged labyrinth weir relationship reduced the predictive errors from 23 to 3.5% (maximum) and 8.9 to 0.9% (average), relative to the experimental data. [ABSTRACT FROM AUTHOR]

The sharp-crested weir is the most commonly used device in channels for flow measurement and flow regulation due to its simplicity. Attempts have been made to study in detail the flow over different shapes of normal conventional weirs, side weirs, and oblique weirs. Most of the investigators have expressed the discharge coefficient as a function of various parameters. The concern of this paper is to study flow over an inclined inverted triangular notch weir. Based on experimental work on 0° (normal) and 15, 30, 45, and 60° weirs, the writers have established an equation for discharge in terms of the inclination angle of the weir plane with the plane normal to the flow axis. A new general algebraic optimization procedure has been developed for evolving a linear head-discharge relationship for an inclined inverted V-notch (IIVN), which is relatively superior to similar procedures developed earlier. It has been shown that the IIVN does not lose its near-linear discharging characteristics even when it is inclined to the channel bed. The discharge estimated by the linear discharge-head relationship has been found to be in good agreement with the actual discharges well within a ±5% error. Further, the advantages of the IIVN as a flow measuring and flow control device have been highlighted. [ABSTRACT FROM AUTHOR]

This study analyzes the air–water flow properties in overflow nappe jets. Data were measured in several cross-sections of rectangular free-falling jets downstream of a sharp-crested weir, with a maximum fall distance of 2.0 m. The flow properties were obtained using a conductivity phase-detection probe. Furthermore, a back-flushing Pitot-Prandtl probe was used in order to obtain the velocity profiles. Five specific flows rates were analyzed, from 0.024 to 0.096 m3/s/m. The measurements of the air–water flow allowed us to characterize the increment of the air entrainment during the fall, affecting the flow characteristic distributions, reducing the non-aerated water inner core, and increasing the lateral spread, thereby leading to changes in the jet thickness. The results showed slight differences between the upper and lower nappe trajectories. The experimental data of the jet thickness related to a local void fraction of 50% seemed to be similar to the jet thickness due only to gravitational effects until the break-up length was reached. The amount of energy tended to remain constant until the falling distance was over 15 times greater than the total energy head over the weir crest, a distance at which the entrained air affected the entire cross-section, and the non-aerated core tended to disappear. The new experiments related with air–water properties in free-falling jets allow us to improve the current knowledge of turbulent rectangular jets. [ABSTRACT FROM AUTHOR]

The article discusses research which investigated V-shaped multislit weir systems, conducted by A. S. Ramamurthy and colleagues. Topics explored include the flow measurement and control associated with multislit weirs, a comparison between the discharge coefficient data and the explicit and implicit representations of the Reynolds number for V-shaped multislit weirs, and the percentage of error recorded for the discharge coefficient data.

A new elliptical sharp-crested weir was developed to address discharge, pollution, and maintenance concerns associated with detention ponds. The elliptical weir was specifically designed to decrease the time and cost associated with clearing debris following storm events. A Froude-scale physical model was constructed and stage-discharge data were collected to analyze the stage-discharge relationship of the new weir. A total of 45 steady-state tests were conducted encompassing nine unique weir geometric configurations. The ellipse ratio varied from 12 to 16, and the gap width varied from 1.5 to 9.1 mm (0.005 to 0.030 ft). Empirical power-regression coefficients were determined for each of the configurations. Also, a theoretical rating equation was derived for the elliptical weir and a discharge coefficient of 0.642 was determined from analyzing the physical-model data. Trapezoidal integral approximation was used to develop an explicit approximate solution for the theoretical rating equation. By using the trapezoidal integral approximation, measured discharges were predicted with a mean absolute percent error of 3.55% for the data set, excluding discharges lower than (0.10 cfs). [ABSTRACT FROM AUTHOR]

This work presents a critical analysis of submerged flow over rectangular weirs of finite crest length. For finite crest length weirs, because the existing data sets are not extensive, new experiments for these weirs with sharp-edged and rounded crest were conducted. Based on these data, a diagram is developed to show the variation of the normalized tailwater depth with where is the free flow head and is the length of the crest, to predict the onset of submergence or the modular limit. Water surface profiles of flow over weirs of finite crest length with square-edge and rounded crests were plotted to study the formation of waves in modular and submerged conditions. Characteristics length scales such as wave length and amplitude at the modularity limit and the location of the first trough downstream of the weir were measured to generalize surface profiles at different flow discharges. An empirical equation for the discharge reduction factor was also formulated. This equation has two exponents with different values for several classes of finite crest length weirs with either square edged or rounded crest. [ABSTRACT FROM AUTHOR]

Triangular weirs are commonly used to measure discharge in open channel flow, representing an inexpensive, reliable methodology to monitor water allocation. In this work, a low-speed photographic technique was used to characterize the upper and lower nappe profiles of flow over fully aerated triangular weirs. A total of 112 experiments were performed covering a range of weir vertex angles (from 30° to 90°), crest elevations (8 or 10 cm), and discharges (). The experimental nappe profiles were mathematically modeled and combined with elements of free-vortex theory to derive a predictive equation for the weir discharge coefficient. Comparisons were established between measured , the proposed discharge coefficient equation, and discharge coefficient equations identified in the literature. The proposed equation predicts with a mean estimation error (MEE) of 0.001, a root-mean square error (RMSE) of 0.004, and an index of agreement (IA) of 0.984. In the experimental conditions of this study, this performance slightly improves that of the equation proposed by Greve in 1932, and showed the same absolute value of MEE but lower values of RMSE and IA. [ABSTRACT FROM AUTHOR]