A preliminary experimental work were conducted to evaluate the hydraulics performance of half circle notch

sharp-crested weir. The evaluation of results shows that , the variation of flow width crossing the circular notch
not only affects the value of discharge coefficient but also have an influence on the exponent of the flow rate
formula , the regression of the experimental results refers that the exponent of head would approaching to,2,
compared to,1.5, and 2.5 those featured the fully contracted rectangular and V-notch weirs predictive formulas
respectively. According to this finding the new formulas related the weir coefficient, C w and the discharge
coefficient ,C d , were correlated corresponding with regressed curves to be helpful for designers related to this
kind of weir. The study , also shows that , in spite of the simplicity of a present equation , its usefulness were at
an acceptable error compared with previously presented by another researchers that have more complicated in
configuration and related factors , wherefore , it may be impractical. Thereby the simplicity and an acceptable
precise of a present formula refers to be a useful tool for practical purposes .

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Discharge Coefficient of Half Circle Notch Sharp-Crested Weirs: Preliminary

Experimental Approach
Jaafar Maatooq

October 2012 with 572 Reads

The flow of water over a trapezoidal, broad-crested, or embankment weir with varying upstream and
downstream slopes has been investigated. Data are presented comparing the effect of slopes of 2H: 1V, 1H: 1V
and vertical in various combinations on the upstream and downstream faces of the weir. Pressure and surface
profiles were self-similar for all cases tested. Increasing the upstream slope to the vertical decreased the height
of the surface profile and, hence, the static pressure of the crest. It also reduced the discharge coefficient. The
variation in downstream static pressures was negligible though. Varying the downstream slope had a negligible
effect on the surface and pressure profiles over the weir. Changes in flow were constrained to the region
downstream of the crest. Cavitation could occur at the downstream corner of the weir if the upstream head was
sufficiently high and a sloped face was used. This paper presents data that will be of use in the design of
hydraulic structures for flow control and measurement.

Hydraulics of Broad-Crested Weirs with Varying Side Slopes

Article in Journal of Irrigation and Drainage Engineering 135(1) · February 2009 with 321 Reads

J. E. Sargison
The capacity of an existing spillway can be increased by lengthening the spillway crest, or increasingthe
discharge coefficient or operating head, or any combination of these approaches. Constructing a labyrinthweir in
an existing spillway is an example of an effective way to increases the spillway crest length and
thecorresponding discharge capacity for the same operating head. Thus, labyrinth weir are well suited to the
siteswhere increasing the spillway width and maximum reservoir water surface elevation would be difficult, yet
largerdischarge are needed. This type of weir consists of series of slender walls having a repeating shape in
plan,usually triangular or trapezoidal with vertical upstream faces and steeply slopping downstream faces. Over
thepast few decades, labyrinth spillways have been constructed throughout the world. Definite guidelines
andtheoretical procedures pertaining to hydraulic design of this type of weir not completely established. There
aremany factors such as head to crest height ratio, vertical aspect ratio, side wall angle, apex width and
approachand conveyance channel conditions that influence the capacity of weir and hence the hydraulic design
oflabyrinth weir. In this paper extensive physical modeling of the labyrinth spillway, primarily flume studies,
hasbeen performed, resulting in the development of Lux and Tullis methods are compared for a given
labyrinthspillway. Further testing to define labyrinth hydraulic behaviour for this lower vertical aspect ratio
(w/p) isrecommended.

World Applied Sciences Journal 11 (7): 835-839, 2010ISSN 1818-4952© IDOSI Publications, 2010Corresponding
Author: B.V. Khode, Asstt. Professor, G.H.Raisoni College of Engineering, Nagpur, India.835 Evaluation and
Analysis of Crest Coefficient for Labyrinth WeirB.V. Khode and A.R. Tembhurk
According to the experimental results, values of discharge coefficient for trapezoidal, semicircular and
compound semicircular-trapezoidal weirs
are 0.6848, 0.5749 and 0.7895 respectively. In each of these weirs coefficient of determination (R2) are
equal to 0.9984, 0.9991, and 0.9987 and
root mean square error (RMSE) equal to 0.0021, 0.0033 and 0.0007 respectively. RMSE presents mean
square error between observed and
calculated values and the less it is the more accurate the equations are. Values of RMSE release that in
this study a semicircular-trapezoidal weir,
has much more accuracy than other ones.

Determination of Semicircular-Trapezoidal Weir Discharge Coefficient

Article (PDF Available) · June 2016 with 897 Reads

Vahid Azimi
Weirs are a type of hydraulic structure, used for water level adjustment, flow measurement, and diversion of
water in irrigation systems. In this study, experiments were conducted on sharp-crested weirs under free-flow
conditions and an optimization method was used to determine the best form of the discharge coefficient
equation based on the coefficient of determination (R2) and root mean square error (RMSE). The ability of the
numerical method to simulate the flow over the weir was also investigated using Fluent software. Results
showed that, with an increase of the ratio of the head over the weir crest to the weir height (h/P), the discharge
coefficient decreased nonlinearly and reached a constant value of 0.7 for h/P > 0.6. The best form of the
discharge coefficient equation predicted the discharge coefficient well and percent errors were within a ±5%
error limit. Numerical results of the discharge coefficient showed strong agreement with the experimental data.
Variation of the discharge coefficient with Reynolds numbers showed that the discharge coefficient reached a
constant value of 0.7 when h/P > 0.6 and Re > 20000

Volume 11, Issue 1, January 2018, Pages 75-80

Experimental and numerical analysis of flow over a rectangular full-width

sharp-crested weir
Author links open overlay panelGhorbanMahtabia

HadiArvanaghib
Labyrinth weirs provide an effective means to increase the spillway discharge capacity of dams and are
often considered for renovation projects required due to an increase in expected flood inflow to the
reservoir of an existing dam. Free crest spillways are hydraulically efficient and safe in operation. Since their
discharge capacity is directly proportional to the crest length several types have been developed with the
purpose to increase the length of the latter. In recent years many research investigations have considered
the hydraulic performance of labyrinth weirs, particularly as dependent on the geometric features. The
previous workhas improved the design basis for such weirs. In the present study, discharge coefficients
were experimentally determined for sharp crested trapezoidal labyrinth weirs of varying side wall angle (α).
The experimental results of 21 physical models were used to develop a hydraulic design and analysis
method for labyrinth weirs. The present research primarily aims at evaluating various characteristics of a
flow-over labyrinth weir by conducting experimentations at wider range of values for important
parameters.

Discharge Coefficient of Sharp-Crested Trapezoidal

Labyrinth Weirs
Omer BILHAN1M. Emin EMIROGLU
INTERNATIONAL JOURNAL OF ELECTRONICS, MECHANICAL AND MECHATRONICS
ENGINEERING Vol.6 Num.4 - 2016 (1305-1316)
In the present study, ANN models have been developed to predict the discharge coefficients of oblique sharp-
crested weirs for free and submerged flow cases using Borghei et al.’s experimental data. The discharge
coefficients predicted by ANN models are then used to predict the discharges. The results so obtained are
compared with the traditional regression model analysis performed by Borghei et al. (2003) in which the
prediction error in the discharge was found within the range of ±5%. On the other hand, the developed ANN
models predict the discharge coefficients as well as discharges within the error range of ±1%. Furthermore,
sensitivity analysis of developed ANN models have been carried out for all the parameters (weir height, oblique
weir length, head over weir and downstream head over weir) involved in the study and it was found that the
weir length (L) is the most and weir height (P) is the least sensitive input variable to ANN-1 model. In the case of
ANN-2 model, weir length (L) is the most and downstream head over weir (Hd) is the least sensitive input
variable.

Discharge coefficient of oblique sharp crested weir for free and submerged
flow using trained ANN model

Peer review under responsibility of National

Water Research Center.
View all notes
Md. Ayaz & Talib Mansoor

Pages 192-212 | Received 06 Apr 2018, Accepted 02 Oct 2018, Published online: 03 May 2019
Side weirs are useful and common devices in flow measurement issues. These weirs have been extensively used
in hydraulic and environmental engineering applications. The characteristic of flow over side weirs are
completely different from that over a weir normal to the approach channel. An accurate flow modeling over a
side weir mainly depends on the proper estimation of discharge coefficient. In this study, the potential of two
different machine learning methods, namely support vector machines combined with genetic algorithm (SVM–
GA) and gene expression programming (GEP) were evaluated for predicting trapezoidal and rectangular sharp-
crested side weirs discharge coefficient. Correlation coefficient (R), mean normalize error (MNE), and Nash–
Sutcliffe index (NS) statistics are used for the evaluation of the model’s performances. The results showed that
the SVM–GA model with R = 0.97, NS = 0.94, and MNE = 13% for trapezoidal side weir and R = 0.97, NS = 0.91,
and MNE = 18% for rectangular side weir, in test period gives more accurate results than GEP. The results verify
that the SVM–GA model can process used data series by better generalization ability and higher prediction
accuracy.

Predicting trapezoidal and rectangular side weirs discharge coefficient using

machine learning methods
Kiyoumars Roushangar, Reza Khoshkanar & Jalal Shiri

Pages 254-261 | Received 29 Nov 2015, Accepted 09 Apr 2016, Published online: 25 Apr 2016
In many hydraulic structures, side weirs have a critical role. Accurately predicting the discharge coefficient is one
of the most important stages in the side weir design process. In the present paper, a new high efficient side weir
is investigated. To simulate the discharge coefficient of these side weirs, three novel soft computing methods
are used. The process includes modeling the discharge coefficient with the hybrid Adaptive Neuro-Fuzzy
Interface System (ANFIS) and three optimization algorithms, namely Differential Evaluation (ANFIS-DE), Genetic
Algorithm (ANFIS-GA) and Particle Swarm Optimization (ANFIS-PSO). In addition, sensitivity analysis is done to
find the most efficient input variables for modeling the discharge coefficient of these types of side weirs.
According to the results, the ANFIS method has higher performance when using simpler input variables. In
addition, the ANFIS-DE with RMSE of 0.077 has higher performance than the ANFIS-GA and ANFIS-PSO methods
with RMSE of 0.079 and 0.096, respectively.

Applied Water Science

March 2018, 8:10 | Cite as

New type side weir discharge coefficient simulation using three novel hybrid
adaptive neuro-fuzzy inference systems

 Authors
 Authors and affiliations

 Hossein Bonakdari
 Amir Hossein Zaji
This study focused on hydraulic characteristics around a gear-shaped weir in a straight channel. Systematic
experiments were carried out for weirs with two different gear heights and eight groups of geometrical
parameters. The impacts of various geometrical parameters of gear-shaped weirs on the discharge capacity
were investigated. The following conclusions are drawn from the experimental study: (1) The discharge
coefficient () was influenced by the size of the gear: at a constant discharge, the weir with larger values of a/b (a
is the width of the gear, and b is the width between the two neighboring gears) and a/c (c is the height of the
gear) had a smaller value of . The discharge capacity of the gear-shaped weir was influenced by the water depth
in the weir. (2) For type C1 with a gear height of 0.01 m, when the discharge was less than 60 m3/h and < 1.0 ( is
the water depth at the low weir crest, and P is the weir height), significantly increased with the discharge and ;
with further increases of the discharge and , showed insignificant decreases and fluctuated within small ranges.
For type C2 with a gear height of 0.02 m, when the discharge was less than 60 m3/h and < 1.0, significantly
increased with the discharge and ; when the discharge was larger than 60 m3/h and > 1.0, slowly decreased with
the increases of the discharge and for ≤ 1.0 and ≤ 1.0, and slowly increased with the discharge and for > 1.0
and > 1.0. (3) A formula of for gear-shaped weirs was established based on the principle of weir flow, with
consideration of the water depth in the weir, the weir height and width, and the height of the gear.

Volume 11, Issue 3, July 2018, Pages 258-264

Experimental study on discharge coefficient of a gear-shaped weir

Author links open overlay panelJingZhangaQianChangbQing-huaZhanga

Shu-ningLia