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Flow Measurement and Instrumentation 22 (2011) 319330
Contents lists available at ScienceDirect
Flow Measurement and Instrumentation
journal homepage: www.elsevier.com/locate/flowmeasinst
Discharging capacity of rectangular side weirs in straight open channels
M. Emin Emiroglu a,, Hayrullah Agaccioglu b, Nihat Kaya aa Firat University, Engineering Faculty, Department of Civil Engineering, 23119, Elazig, Turkeyb Yildiz Technical University, Faculty of Civil Engineering, 34210, Esenler, Istanbul, Turkey
a r t i c l e i n f o
Article history:
Received 28 December 2009
Received in revised form6 December 2010
Accepted 5 April 2011
Keywords:
Side weir
Water discharge
Discharge coefficient
Intake
Channel flow
Flow measurement
Hydraulic structure
a b s t r a c t
A side weir is a hydraulic control structure used in irrigation and drainage systems and combined sewersystems. A comprehensive laboratory study, including 843 tests for the discharge coefficient of a sharp-
crested rectangular side weir in a straight channel, was conducted in a large physical model undersubcritical flow conditions. The discharge coefficient is a function of the upstream Froude number, the
ratios of weir length to channel width, weir length to flow depth, and weir height to flow depth. Anequation was developed considering all dimensional parameters for discharge coefficient of the sharp-
crested rectangular side weir. Theaverage error of theproposed equation is 4.54%.The present study datawere compared with ten different discharge coefficient equations developed by several researchers. Thestudy also presents water surface profile and surface velocity streamlines.
2011 Elsevier Ltd. All rights reserved.
1. Introduction
Side weirs have been extensively used in hydraulic andenvironmental engineering applications. They are substantial partsof distribution channels of irrigation systems and water andwastewater treatment plants. Side weirs are also used as anemergency structure in many hydraulic structures. The side weir isnormally installed at one side of a channel to divert flow laterally.
Nandesamoorthy et al. [1], Subramanya et al. [2], Yu-tech [3],Ranga Raju et al. [4], Hager [5], Cheong [6], Singh et al. [7], Jaliliet al. [8], and Borghei et al. [9] gave equations for dischargecoefficients for rectangular, sharp-crested side weirs based onexperimental results. Swamee et al. [10] used an elementaryanalysis approach to estimate the discharge coefficient in smoothside weirs through an elementary strip along the side weirs.Ghodsian [11] studied behavior in the rectangular side weir underconditions of supercritical flow. Khorchani et al. [12] studied theflow over side weirs with a full-scale experiment using digitalcameras. Muslu [13], Yksel [14] and Muslu et al. [15] usednumericalanalysisto analyze the flow over a rectangular side weir.
Considering the discharge dQ through an elementary strip oflengthds along theside weir in a rectangular main channel in termsof De Marchis [16] equation, one gets
q = dQds
= 23
Cd
2g(h p)3/2 (1)
Corresponding author. Tel.: +90 4242370000x5441; fax: +90 4242415526.E-mail addresses: [email protected](M.E. Emiroglu), [email protected]
(H. Agaccioglu), [email protected](N. Kaya).
where Q is the discharge in the main channel, s is the distancefrom the beginning of the side weir, dQ/ds (or q) is the discharge
overflow per unit length of the side weir, g is the accelerationdue to gravity, p the is height of the side weir, h is the depthof flow at the section s (at s = 0 : h = h1 and Q = Q1), (h p) isthe pressure head on the weir and Cd is the discharge coefficientof the rectangular side weir. Thus, Qs = q.L, in which Qs is theflow rate over theside weir and L is the length ofthe side weir. Thedischarge coefficient (Cd) depends on the following dimensionlessparameters [2,7,9,17,18].
Cd = f1
F1 =V1gh1
,L
b,
L
h1,
p
h1, , S0
(2)
where F1 is the upstream Froude number at the beginning of theside weir in the main channel, V1 is the mean velocity of flow atthe upstream section of the side weir in the main channel, L is the
width of the side weir, b is the width of the main channel, h1 isthe depth of flow on the upstream end of the side weir in the mainchannel centerline, is the deviation angle of flow, and S0 is thechannel slope. Notations and a definition sketch of subcritical flowover a rectangular side weir can be seen in Fig. 1.
The water nape deviationor thedeflection angle , isdefinedasthe deflection of the side weir nape from the water surface towardthe weir side which is formulated as follows [2]:
sin =
1
V1
Vs
2(3)
in which, Vs is velocity of flow dQs over the brink. Accordingto Eq. (3), takes different values for each fluid particle and
0955-5986/$ see front matter 2011 Elsevier Ltd. All rights reserved.doi:10.1016/j.flowmeasinst.2011.04.003
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Nomenclature
b Width of channel, m
Cd Side weir discharge coefficient,E Specific energy, mF1 Froude number at upstream end of side weir,
g Acceleration due to gravity, m/s2
h Main channel depth, mh1 Flow depth at upstream end of side weir at main
channel centerline, mh2 Flow depth at downstream end of side weir at
channel centerline, mL Length (width) of side weir, m
p Height of weir crest, mQ Discharge in the main channel, m3/sQ0 Discharge at upstream of side weir at main channel
centerline, m3/sQ1 Discharge at upstream end of side weir at main
channel centerline, m3/sQ2 Discharge at downstream end of side weir at main
channel centerline, m3/s
Qs Total flow rate over the side weir, m3
/sq Discharge per unit length over side weir, m2/sdQ/ds = dQs Discharge per unit length of side weir, m2/sR Correlation coefficient,S0 Channel slope,
s Distance along side weir measured from upstreamend of side weir, m
V Mean velocity in any section of channel, m/sV1 Mean velocity of flow at upstream end of side weir,
m/sV2 Mean velocity of flow at downstream end of side
weir, m/sVs Velocity of flow dQs over the brink, m/s Deviation angle of flow,
varies with the Froude number, which changes along the side weir
due to spilling over the side weir. The deviation angle increases
toward theweirsidewhenthe Froude number in themainchannel
decreases toward the downstream direction. El-Khashab [17]
also mentioned that the dimensionless length of the side weir
(L/b) includes the effect of the deviation angle on the discharge
coefficient. Therefore, the deviation angle is not specified in
the side weir discharge coefficient equations in the literature.
Therefore, the effect of on Cd is not considered separately in
the present study. In addition, Borghei et al. [9] reported that
a
b
c
Fig. 1. Definition sketch of subcritical flow over a rectangular side weir.
the channel slope can be ignored in conditions of subcriticalflow. Thus, dimensionless parameters for rectangular side weirdischarge coefficient can be formulated as shown in Eq. (4).
Cd = f2
F1 =V1gh1
,L
b,
L
h1,
p
h1
. (4)
The flowovera side weir is a typical case of spatially varied flowwith decreasing discharge. Like normal weirs, side weirs may be
sharp or broad-crested. The flow in the main channel along a sideweir may be subcritical or supercritical. In side weir applications,the most common form is a sharp-crested rectangular design. Inaddition, the most common flow type is subcritical. Therefore, thisweir type and flow regime are considered in the present study.Table 1 shows equations presented in the literature, relating Cdfor rectangular side weir located on straight channels. As seenin Table 1, Froude number is taken into account in all of theequations. However, the dimensionless parameter L/h1 is not seenin any of the equations previously presented in the literature. Itwas mentioned by Subramanya et al. [2], El-Khashab [17], Singhet al. [7], and Durga Rao et al. [18] that the L/h1 dimensionless
Table 1
Side weir discharge coefficient equations presented in the literature for straight channels.
No. Discharge coefficient equations for rectangular side weirs Source
1 Cd = 0.432
2F21
1+2F21
0.5Nandesamoorthy et al. [1]
2 Cd = 0.611
1
3F21
F21+2
= 0.864
1F2
1
2+F21
0.5Subramanya et al. [2]
3 Cd = 0.623 0.222F1 Yu-Tech [3]4 Cd = 0.81 0.6 F1 Ranga Raju et al. [4]5 Cd = 0.485
2+F2
1
2+3 F21
0.5Hager [5]
6 Cd = 0.45 0.221F21 Cheong [6]7 Cd = 0.33 0.18F1 + 0.49
p
h1
Singh et al. [7]
8 Cd = 0.71 0.41F1 0.22
p
h1
Jalili et al. [8]
9 Cd = 0.7 0.48F1 0.3
p
h1
+ 0.06 L
bBorghei et al. [9]
10 Cd = 1.06[ 14.14p8.15p+h1 10
+ h1h1+p15]0.1
Swamee et al. [10]
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Table 2
Range of variables for present study and several studies.
Variable Source
Present study Borghei
et al. [9]
Singh
et al. [7]
Cheong [6] Subramanya
et al. [2]
Agaccioglu et al. [21]
Channel width (m) 0.50 0.30 0.25 0.350.67 0.2480.61 0.40
Discharge (L/s) 10150 35100 1014 3.575 7.9568.8
Weir length (m) 0.151.50 0.200.70 0.100.20 0.280.97 0.250.75
Weir height (m) 0.120.20 0.010.19 0.060.12 0.080.51 0.120.16Froude number 0.080.92 0.10.9 0.400.90 0.240.99 0.024.3 0.0770.869
L/b ratio (max.) 0.303.00 2.30 0.50 1.45 0.21.0 0.6251.875
p/h1 ratio 0.340.91 0.420.85 0.20.96 0.5420.877
Dimensionless parameters in
equation
F1, L/b, L/h1 and,
p/h1
F1, L/b, and
p/h1
F1 and p/h1 F1 F1 F1, L/b
Number of runs 843 253 78 200 320 (for straight channel)
Fig. 2. Experimental arrangement.
parameter is among the parameters that affect the discharge
coefficient. Therefore, L/h1 and L/b dimensionless parametershave
been tested together with p/h1 parameter for the experimental
data. The range of test variables used in the present study is given
Table 2.
The purpose of this study is to systematically investigate
the effect of side weir length in relation to the dischargecoefficient under subcritical flow conditions, using a broad range
of experiments, and considered together with the other effective
dimensionless parameters. Additionally, water surface profiles and
surface velocity streamlines were investigated in the weir region.
2. Experimental set-up and experiments
Experiments were carried out in the Hydraulic Laboratory of
Firat University, Elazig, Turkey. A schematic representation of the
experimental set-up is shown in Fig. 2. The experimental set-upconsists of a main channel and a discharge collection channel. The
main channel is 12 m long and the bed has a rectangular cross
section. The main channel is 0.5 m wide, 0.5 m deep and has a0.001 bed slope. The channel consists of a smooth horizontal well-
painted steel bed with a vertical glass sidewall. A sluice gate is
fitted at the end of themainchannel in orderto control flow depth.The collection channel is 0.5 m wide and 0.7 m deep, and situated
parallel to the main channel. The width of the collection channel
acrossthe side weiris 1.3 m and it isconstructedas a circularshape
to provide free overflow conditions over the side weirs. A Mitutoyo
brand digital point gauge with0.01 mm sensitivity is fitted 0.4 mfrom the weir. The side weirs were fabricated from steel plates,
which are sharp edged and fully aerated and installed flush with
the main channel bank.
Water for the main channel was supplied through a supply
pipe from a sump and the flow was controlled by a gate valve.
In previous studies, experiments to determine the dischargecoefficient were generally conducted within a narrower range
Fig. 3. Locations where water level was measured.
of discharges than those examined in the present study. In thisstudy, the flow rate was between 0.010 and 0.150 m3/s and wasmeasured by means of a Siemensbrandelectromagnetic flowmeter(0.01 L/s sensitivity) installed on the supply line. Additionally,the results were compared by a calibrated 90 V-notched weir atthe beginning of the system (Q1). The overflow rate at thesideweirwas obtained by calibrated standard rectangular weir, located atthe downstream end of the collection channel (Qs).
Water depth was measured using the point gauge at the sideweir region, along the channel centerline (C2, D2 and E2) and the
weir side of the main channel (C1, D1 and E1), as seen in Fig. 5.Water surface measurements were made using a special type of
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0.00 0.20 0.40 0.60 0.80 1.000.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
Rectangular side weir
p=0.12 m, L=0.75 m
Depthofflowinm
Longitudinal section in m
F1=0.28, Surface profile along the centerline
0.00 0.20 0.40 0.60 0.80 1.000.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
Rectangular side weir
p=0.12 m, L=0.75 m
Depthofflowin
m
Longitudinal section in m
F1=0.28, Surface profile along the weir-side
0.00 0.20 0.40 0.60 0.80 1.000.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
Rectangular side weir
p=0.16 m, L=0.75 m
Depthofflowinm
Longitudinal section in m
F1=0.39, Surface profile along the centerline
0.00 0.20 0.40 0.60 0.80 1.000.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
Rectangular side weir
p=0.16 m, L=0.75 m
Depthofflowinm
Longitudinal section in m
F1=0.39, Surface profile along the weir-side
0.00 0.20 0.40 0.60 0.80 1.00
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
o.50
Rectangular side weir
p=0.20 m, L=0.75 m
Depthofflowinm
Longitudinal section in m
F1=0.63, Surface profile along the centerline
0.00 0.20 0.40 0.60 0.80 1.000.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
Rectangular side weir
p=0.20 m, L=0.75 m
Depthofflowinm
Longitudinal section in m
F1=0.63, Surface profile along the weir-side
Fig. 4. Water surface profiles along the weir side and centerline at straight channel.
measurement car which can move in both x and y directions on a
rail (see Fig. 3). Velocities were measured using a Nortek Acoustic
Doppler velocity meter with high sensitivity.
Experiments were conducted for subcritical flow, stable flow
and free overflow conditions. Coleman et al. [19] stated that
minimum nape height should not be less than 0.019 m because of
the surface tension over the weir crest. Therefore, minimum nape
height was taken into account as 0.020 m. The experiments were
conducted for five different lengths of the weir (0.15, 0.25, 0.50,
0.75, and 1.50 m) and three different heights of the weir (0.12,0.16, and 0.20 m). As seen in Table 2, the length of side weir, L was
between 0.20 and 0.70 m to achieve the discharge coefficient of
rectangular side weir. Thelengthof theside weir (L) is an important
parameter for discharge coefficient of the side weir. Therefore, the
dimensionless parameters, L/b and L/h1, were studied in detail in
the present study. The length of the side weir (L) was considered
between 0.15 and 1.50 m in the present study, permitting the
dimensionless L/b parameter to be tested across a wide range (i.e.,
L/b = 0.3 to 3.0).After the completion of a good physical description of the
rectangular side weir flow at the straight rectangular channel, sideweir flow rates were tested for different Froude numbers, different
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a
b
Fig. 5. Definition sketch: velocity streamlines for L/b = 1.50: (a) F1 < 0.28; (b) F1 > 0.42.
p/h1 ratios, different L/b ratios, and different L/h1 ratios in orderto determine the variation of the discharge coefficient (Table 2).A total of 910 test runs for discharge coefficient and water level
measurements were performed in the present study.
3. Experimental results and analysis
3.1. Water level profile
Water surface levels were measured both along the channelcenterline (C2, D2 and E2) and the weir side of the main channel(C1, D1 and E1) to describe the flow structure in the main channel.As shown in Fig. 4, the water depth at the upstream end of the
side weir is lower than that at the downstream end of the sideweir. This same situation is observed in all previous experimentalruns. Water surface profiles along side weirs drop slightly at theupstream end of the weir crest. As El-Khashab [17] and Emirogluet al. [20] reported in previous studies, this is due to the side weir
entrance effect at the upstream end. The water level then quicklyrises toward the downstream end of theweir. The rate of rise at thewater level decreases substantially after the midspan of the sideweir crest. The change in water level is not noticeable in almost
the last third of the weir length, where the water surface is almosthorizontal. This behavior of the water surface is due to the effectof secondary flow created by lateral flow. Fig. 4 also indicates thatthe water surface level along the main channel centerline is almosthorizontal. This shows that the side weir entrance effect does notspread as for as the centerline of themain channel, but occurs only
near the weir crest.Fig. 5(a) and (b) show surface velocity streamlines for F1 0.42, respectively. The effect of lateral flow issignificant, especially for high overflow conditions. The effect of
the breakdown in flow near the end of the weir at the channelside is obvious near the channel bed. Since the low velocity layerstarts to exist, the path of maximum velocity gradually movesfrom a position toward the side weir toward the centerline of the
main channel passing through the separation zone. The separationzone occurs due to decreasing momentum in the direction of the
main channel flow overflowing the collection channel. The areaoccupied by this zone is always near the bed, from 0.2 to 0.4 times
the mean depth of flow at that section along the weir length, andvaries with this area occupied by the low velocity layer. A reverseflow at the downstream end of the side weir was also observed
when the Froude number is small. When F1 > 0.42, the reserveflow area diminishes and weak standing waves are formed. WhenF1 > 0.85, a surface jump occurs earlier at the end of side weirs,
because lateral flow reduces the potential energy and increasesthe kinetic energy of the flow in the downstream direction withinthe main channel. The existence of a stagnation zone is due to thediversion that occurs from the path of maximum velocity thread.
The location of the stagnation zone and the reverse flow areadepend especially on the Froude number F1 at the upstream sideof the weir in the main channel in addition to the length of the
side weir and thenapethickness over the side weir. When theflowintensity or momentum toward the downstream direction in themain channel increases, then the reverse flow area moves towardthe downstream end of the side weir.
3.2. Cd coefficient
A series of 843 experimental runs were conducted to determine
the discharge coefficient of sharp-crested rectangular side weirs.The discharge coefficient was computed using De Marchisequation (Eq. (2)). In other words, h1 and Qw were measured for
each side weir configuration in the laboratory. Thus, the dischargecoefficient was computed with Eq. (5) (i.e., De Marchis equation).
Cd =(3/2)Qw
2g(h1 p)3/2L. (5)
To study the effect of parameter p/h1 on discharge coefficients,Cd values were plotted againstp/h1 together with the different L/bratios, as shown in Fig. 6((a)(c)). Experiments were performed for
constantp, b and L with varying depth of flow (h1). In otherwords,the crest heightis 0.12m in Fig. 6(a), 0.16 m in Fig. 6(b), and 0.20m
in Fig. 6(c). As is seen in Fig. 6((a)(c)), Cd values correspondingto the same p/h1 values, especially for high L/b ratios, are very
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324 M.E. Emiroglu et al. / Flow Measurement and Instrumentation 22 (2011) 319330
a b
c
Fig. 6. Cd vs. different p/h1 values for L/b = 0.3; L/b = 1.5, and L/b = 3.0 (a) p/b = 0.24; (b) p/b = 0.32; and (c) p/b = 0.24.
Fig. 7. Side weir coefficient (Cd) vs. F1 together with different dimensionless weir
heights (p/h1).
different from each other.The scatterof thedata is attributed to theeffect of the other parameters, such as F1 and L/h1 parameters. Thevariation ofCd with p/h1 shows a decreasing tendency for L/b =0.3. This decreasingtendency forL/b < 1 is similar to that reportedin previous studies [8,9,21,22]. The variation of Cd with p/h1 for
L/b = 1 to 1.5 shows a slightly increasing tendency. However,for L/b = 3.0, this increasing tendency is very high. The intensity
of secondary flow due to lateral flow is more dominant whena side weir is relatively long. Therefore, the deviation angle andthe kinetic energy caused by the secondary flow toward the sideweir increases when the relative side weir length (or the overflowlength) increases. Thus, it can be conclusively stated that p/h1 isan important parameter for the discharge coefficient. Therefore,
the effect of p/h1 on Cd has been investigated in detail for allrectangular side weirs.
Fig. 7 shows Cd plotted against F1 together with differentdimensionless weir heights (p/h1) and weir lengths (L/b). The
p/h1 and L/b values were kept constant, and several series of
experiments with different Froude numbers were performed.Although the variation in Cd value does not change greatly with
increasing p/h1 value for L/b = 0.3, the values of Cd increasesignificantly with increasing p/h1 for L/b = 3.0. Fig. 7 clearlyshows the effect of both p/h1 and L/b on Cd . The effect of p/h1on Cd can be explained with reference to the discontinuity region.This discontinuityregion hasa strongsecondary motionnext to theboundary of the weir side: the intensity of the secondary motion
next to the boundary depends on the crest height of the side weirand decreases with increasing crest height of the side weir, dueto the friction of the weir surface. The intensity of secondary flowcreated by lateral flow is defined as the ratio of the mean kineticenergyof the lateral motionto the total kinetic energyof main flowat a given cross section.
The variation of Cd with F1 while L/b, p/h1, and L/h1 areconstant is shown in Fig. 8((a)(e)). Moreover, Fig. 8((a)(e)) also
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ab
cd
e
Fig. 8. Cd for different F1 values: (a) p = 0.12 m; (b) p = 0.16 m; (c) p = 0.20 m.
show the effect of L/b parameter on Cd . For L/b = 0.3 and0.5, when the Froude number increases, Cd values decrease. The
results indicate that the discharge coefficient increases when the
Froude number increases for L/b > 1. Agaccioglu et al. [21] and
Kaya et al. [22] also found a similar tendency. The values of Cdhave a tendency to increase with increasing values of L/b. The
variation ofCd with F1 shows an increasing tendency when L/b =3, as shown in Fig. 8(e). The primary reason for this may be the
intensity of secondary flow created by lateral flow turbulence
and velocity streamlines that is oriented toward the side weir. By
the orientation of the velocity streamlines toward side weir, the
occurrence of the stagnation zone plays an important role in flow
interactions. As mentioned above, the strength of the secondary
flow created by the lateral flow was affected by the length of the
side weir crest height of the side weir and the Froude number. Anincrease in the secondary flow causes the growth of the deviation
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a b
c
Fig. 9. Cd for different L/h1 values (a) L/b = 0.3; (b) L/b = 1.5; (c) L/b = 3.0.
angle and kinetic energy toward the side weir when the relative
length of the side weir increases. A review of the literature shows
that previous experiments generally used narrower main channel
widths, smaller weir lengths, and lower flow rates. Most previous
researchers ignored the effect of L/b, L/h1, and p/h1 ratios on the
discharge coefficient. However, Jalili et al. [8] and Borghei et al. [9]
considered the effect ofL/b and p/h1.
Fig. 9 shows theeffect ofL/h1 on Cd, wherep/b is kept constant.
In other words, the crest height is 0.12 m in Fig. 9(a), 0.16 m in
Fig. 9(b), and 0.20 m in Fig. 9(c). However, it was not possible
to take p/h1 and F1 as constants, due to the variation of L/h1ratio. Although many researchers (e.g., El-Khashab [17]; Durga
Rao [18]) stated that the dimensionless parameter L/h1 is effective
on discharge coefficient, the effect of thisdimensionless parameter
was not studied adequately in previous studies. As shown in Fig. 9,
the variation in Cd tends to increase with increasing values of
L/h1. The scatter of the data is attributed to the effect of the other
parameters, such as the Froude number and p/h1 parameters. This
could be observed in almost all of the experiments. For the higher
values ofL/b, the effect ofL/h1 can be seen more clearly. The fact
that the literature studied low L/b ratios more commonly led to
researchers overlooking the real effect of L/h1. The results of the
present study demonstrate conclusively that L/h1 should not be
ignored.
Empirical correlations to predict discharge coefficient Cd weredeveloped for rectangular side weirs according to the results of the
dimensionless analysis. The resulting correlation is given in Eq. (6).
Cd =
0.836 +0.035 + 0.39
p
h1
12.69+ 0.158
L
b
0.59
+ 0.049
L
h1
0.42+ 0.244F2.1251
3.0185.36
(6)
where the weir width L, the channel width b, the height of weir
crestp, and the flow depth h1 are in meters and theFroudenumber
F1 is dimensionless.To evaluate the accuracy of the estimated nonlinear equation,
the root mean square errors (RMSE), the mean absolute error
(MAE), the average percent error (APE) and the correlation
coefficient (R) criteria were used. The value ofR shows the degree
to which two variables are linearly related. Different types of
information about the predictive capabilities of the estimated
nonlinear equation are measured through RMSE and MAE. The
RMSE indicates the goodness of the fit related to high discharge
coefficient values, whereas the MAE provides a more balanced
perspective of the goodness of the fit at moderate discharge
coefficients [23]. The RMSE, MAE and APE are defined as
RMSE = 1NN
i=1(Cd(observed) Cd(estimated))
2
(7)
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Table 3
Comparison of present results with those of researchers in the literature when L/b = 0.3.F1 p/h1 L/b L/h1 Subramanya
et al. [2]
Ranga
Raju
et al. [4]
Hager [5] Singh
et al. [7]
Jalili
et al. [8]
Borghei
et al. [9]
Swamee
etal. [10]
Cheong[6] Nandesamoorthy
et al. [1]
Yu-
Tech [3]
Present
study
0.099 0.74 0.3 0.923 0.426 0.750 0.483 0.674 0.507 0.449 0.712 0.448 0.603 0.601 0.378
0.118 0.84 0.3 1.044 0.423 0.739 0.482 0.718 0.478 0.411 0.701 0.447 0.600 0.597 0.345
0.219 .79 0.3 0.989 0.402 0.678 0.474 0.678 0.446 0.375 0.706 0.439 0.576 0.574 0.318
0.313 0.77 0.3 0.963 0.372 0.622 0.464 0.651 0.412 0.337 0.708 0.428 0.545 0.554 0.3650.153 0.34 0.3 0.426 0.417 0.718 0.480 0.469 0.572 0.542 0.831 0.445 0.594 0.589 0.406
0.198 0.34 0.3 0.424 0.407 0.691 0.476 0.460 0.554 0.521 0.832 0.441 0.583 0.579 0.404
0.228 0.37 0.3 0.466 0.399 0.673 0.473 0.472 0.535 0.497 0.812 0.439 0.574 0.572 0.401
0.267 0.41 0.3 0.518 0.387 0.650 0.469 0.485 0.509 0.465 0.792 0.434 0.561 0.564 0.397
0.294 0.40 0.3 0.505 0.378 0.633 0.466 0.475 0.500 0.456 0.797 0.431 0.552 0.558 0.397
0.226 0.34 0.3 0.422 0.400 0.674 0.473 0.455 0.543 0.508 0.833 0.439 0.574 0.573 0.402
0.257 0.34 0.3 0.422 0.391 0.656 0.470 0.449 0.530 0.493 0.833 0.435 0.565 0.566 0.408
0.634 0.62 0.3 0.772 0.215 0.430 0.420 0.518 0.314 0.229 0.732 0.361 0.407 0.482 0.320
0.650 0.58 0.3 0.728 0.206 0.420 0.418 0.498 0.316 0.231 0.740 0.357 0.400 0.479 0.318
0.088 0.72 0.3 0.541 0.427 0.757 0.483 0.668 0.515 0.459 0.715 0.448 0.605 0.603 0.402
0.119 0.88 0.3 0.661 0.423 0.739 0.482 0.741 0.467 0.396 0.696 0.447 0.600 0.597 0.365
0.143 0.63 0.3 0.473 0.419 0.724 0.480 0.613 0.513 0.460 0.730 0.445 0.596 0.591 0.400
0.123 0.46 0.3 0.347 0.422 0.736 0.481 0.534 0.558 0.520 0.773 0.447 0.600 0.596 0.410
0.167 0.51 0.3 0.379 0.414 0.710 0.478 0.547 0.530 0.486 0.759 0.444 0.590 0.586 0.407
0.172 0.47 0.3 0.353 0.413 0.707 0.478 0.530 0.536 0.494 0.770 0.443 0.589 0.585 0.404
0.515 0.90 0.3 0.674 0.280 0.501 0.437 0.678 0.301 0.201 0.694 0.391 0.460 0.509 0.318
0.590 0.91 0.3 0.681 0.240 0.456 0.426 0.669 0.268 0.162 0.693 0.373 0.426 0.492 0.3270.550 0.87 0.3 0.650 0.262 0.480 0.432 0.656 0.294 0.194 0.697 0.383 0.444 0.501 0.281
0.567 0.83 0.3 0.621 0.253 0.470 0.429 0.634 0.295 0.197 0.701 0.379 0.437 0.497 0.338
0.606 0.87 0.3 0.649 0.231 0.447 0.424 0.645 0.271 0.168 0.698 0.369 0.419 0.489 0.285
0.615 0.82 0.3 0.617 0.226 0.441 0.423 0.623 0.277 0.176 0.702 0.367 0.415 0.487 0.314
0.184 0.86 0.3 1.071 0.410 0.700 0.477 0.717 0.446 0.373 0.698 0.443 0.586 0.582 0.376
0.366 0.86 0.3 1.071 0.351 0.591 0.457 0.684 0.371 0.285 0.698 0.420 0.524 0.542 0.366
0.424 0.86 0.3 1.071 0.325 0.555 0.449 0.674 0.348 0.257 0.698 0.410 0.500 0.529 0.346
0.127 0.89 0.3 0.833 0.422 0.734 0.481 0.743 0.462 0.390 0.695 0.446 0.599 0.595 0.434
0.210 0.89 0.3 0.833 0.404 0.684 0.475 0.728 0.428 0.351 0.695 0.440 0.579 0.576 0.412
0.294 0.89 0.3 0.833 0.378 0.633 0.466 0.713 0.394 0.310 0.695 0.431 0.552 0.558 0.412
0.405 0.91 0.3 0.682 0.334 0.567 0.452 0.703 0.344 0.251 0.693 0.414 0.508 0.533 0.403
0.466 0.91 0.3 0.682 0.305 0.530 0.444 0.692 0.319 0.222 0.693 0.402 0.482 0.520 0.394
0.549 0.75 0.3 0.938 0.262 0.481 0.432 0.599 0.320 0.230 0.711 0.383 0.445 0.501 0.335
0.600 0.75 0.3 0.938 0.235 0.450 0.425 0.590 0.299 0.205 0.711 0.371 0.422 0.490 0.356
0.178 0.80 0.3 0.750 0.412 0.703 0.478 0.690 0.461 0.393 0.705 0.443 0.588 0.584 0.424
0.251 0.80 0.3 0.750 0.392 0.659 0.471 0.677 0.431 0.357 0.705 0.436 0.567 0.567 0.410
0.409 0.83 0.3 0.625 0.332 0.565 0.451 0.665 0.359 0.272 0.701 0.413 0.506 0.532 0.3830.463 0.83 0.3 0.625 0.306 0.532 0.444 0.655 0.337 0.246 0.701 0.403 0.483 0.520 0.375
0.293 0.67 0.3 0.833 0.379 0.634 0.466 0.604 0.443 0.378 0.723 0.431 0.552 0.558 0.391
0.417 0.67 0.3 0.833 0.328 0.560 0.450 0.582 0.392 0.318 0.723 0.412 0.503 0.530 0.382
0.494 0.73 0.3 0.682 0.291 0.513 0.439 0.597 0.347 0.262 0.714 0.396 0.469 0.513 0.388
0.621 0.73 0.3 0.682 0.222 0.437 0.422 0.575 0.295 0.202 0.714 0.365 0.412 0.485 0.342
0.168 0.77 0.3 0.577 0.414 0.709 0.478 0.677 0.472 0.407 0.708 0.444 0.590 0.586 0.414
0.241 0.77 0.3 0.577 0.395 0.666 0.472 0.664 0.442 0.372 0.708 0.437 0.570 0.570 0.409
MAE = 1N
Ni=1
|Cd(observed) Cd(estimated)| (8)
APE = 100N
N
i=1
Cd(observed) Cd(estimated)Cd(observed)
(9)
in which N is the number of data set.
The root mean square error (RMSE), the mean absolute error
(MAE), the average percent error (APE) and correlation coefficient
(R) values for Eq. (6) are 0.0401%, 0.0281%, 4.527% and 0.955%
(i.e., deterministic coefficient R2 = 0.912), respectively. Very goodagreements are obtained between the values observed experi-
mentally and the values computed from the predictive equation
(i.e., Eq. (6)). Thus, the present study introduces an accurate equa-
tion for the coefficient of discharge of the rectangular side weirs in
subcritical flow conditions.
The results of the present study, shown in Tables 35 were
compared with ten previous studies from the literature. As seen
from the relevant tables and also Fig. 10, at lower L/b values, the
results of the present studies are generally compatible with theliterature. The same is nottrue at high L/b ratios. Table 5 and Fig. 11
show that small F1 numbers are compatible with the literaturebut that, at high F1 numbers, the present results differ from thosereported in the literature. This can be explained as follows: at highL/b ratios, the intensity of secondary flow increases even more. Asmentioned above, the present study examined higher L/b ratios.The values obtained using equations produced in other studies are
not very compatible within themselves. This situation can be seenin Tables 35.
4. Conclusions
The present study provides an experimental examination ofthe variation in the discharge coefficient of a rectangular, sharp-crested side weir located on a straight, rectangular main channel.As a result of dimensional analysis, the results indicate that thedimensionless parameters of L/b and L/h1 should not be ignoredin equations determining the discharge coefficient of the sideweir. In this study, the ranges of experimental conditions werebetween 0.08 and 0.92 for F1, 0.34 and 0.91 for p/h1, 0.30 and3.00 for L/b, and 0.347 and 10.71 for L/h1. For L/b = 0.3and 0.5, when the Froude number increases, Cd values decrease.However, the variation ofCd with F1 shows an increasing tendency
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Table 4
Comparison of present results with those in the literature when L/b = 1.5.F1 p/h1 L/b L/h1 Subramanya
et al. [2]
Ranga
Raju
et al. [4]
Hager [5] Singh
et al. [7]
Jalili
et al. [8]
Borghei
et al. [9]
Swamee
etal.[10]
Cheong[6] Nandesamoorthy
et al. [1]
Yu-
Tech[3]
Present
study
0.161 0.78 1.5 4.925 0.415 0.713 0.479 0.687 0.471 0.476 0.706 0.444 0.592 0.587 0.390
0.169 0.82 1.5 5.095 0.414 0.708 0.478 0.699 0.461 0.464 0.703 0.444 0.590 0.585 0.361
0.226 0.70 1.5 4.378 0.400 0.674 0.473 0.633 0.463 0.471 0.718 0.439 0.574 0.573 0.422
0.236 0.72 1.5 4.514 0.397 0.668 0.472 0.641 0.454 0.460 0.715 0.438 0.571 0.570 0.4160.737 0.63 1.5 3.965 0.155 0.368 0.406 0.508 0.268 0.246 0.729 0.330 0.361 0.459 0.501
0.631 0.54 1.5 3.344 0.217 0.431 0.420 0.479 0.333 0.326 0.751 0.362 0.408 0.483 0.485
0.728 0.59 1.5 3.677 0.161 0.373 0.407 0.487 0.282 0.264 0.738 0.333 0.365 0.461 0.525
0.692 0.54 1.5 3.347 0.182 0.395 0.412 0.468 0.309 0.297 0.751 0.344 0.381 0.469 0.506
0.804 0.56 1.5 3.495 0.116 0.328 0.398 0.459 0.257 0.237 0.745 0.307 0.332 0.445 0.562
0.454 0.88 1.5 4.135 0.311 0.537 0.445 0.680 0.330 0.307 0.696 0.404 0.487 0.522 0.390
0.310 0.61 1.5 2.860 0.373 0.624 0.464 0.573 0.449 0.458 0.734 0.429 0.546 0.554 0.426
0.352 0.67 1.5 3.119 0.356 0.599 0.459 0.593 0.419 0.421 0.724 0.423 0.530 0.545 0.448
0.435 0.77 1.5 3.589 0.320 0.549 0.448 0.627 0.363 0.351 0.709 0.408 0.495 0.526 0.466
0.506 0.85 1.5 3.973 0.285 0.506 0.438 0.654 0.316 0.293 0.699 0.393 0.464 0.511 0.451
0.345 0.60 1.5 2.797 0.359 0.603 0.460 0.560 0.437 0.445 0.737 0.424 0.533 0.546 0.428
0.394 0.65 1.5 3.056 0.339 0.574 0.453 0.579 0.405 0.405 0.726 0.416 0.513 0.536 0.440
0.475 0.74 1.5 3.461 0.301 0.525 0.442 0.606 0.353 0.341 0.712 0.400 0.478 0.518 0.483
0.089 0.88 1.5 3.294 0.427 0.757 0.483 0.744 0.480 0.484 0.696 0.448 0.605 0.603 0.447
0.134 0.83 1.5 3.105 0.420 0.729 0.481 0.711 0.473 0.477 0.702 0.446 0.597 0.593 0.440
0.153 0.90 1.5 3.381 0.417 0.718 0.479 0.744 0.449 0.446 0.694 0.445 0.594 0.589 0.401
0.175 0.79 1.5 2.947 0.413 0.705 0.478 0.684 0.465 0.470 0.706 0.443 0.589 0.584 0.444
0.402 0.83 1.5 3.097 0.335 0.569 0.452 0.662 0.364 0.349 0.702 0.414 0.509 0.534 0.497
0.453 0.89 1.5 3.356 0.312 0.538 0.445 0.687 0.327 0.304 0.695 0.405 0.487 0.522 0.527
0.304 0.63 1.5 2.367 0.375 0.628 0.465 0.585 0.447 0.455 0.730 0.430 0.548 0.556 0.437
0.360 0.71 1.5 2.647 0.353 0.594 0.458 0.611 0.407 0.406 0.717 0.421 0.527 0.543 0.469
0.425 0.79 1.5 2.956 0.325 0.555 0.449 0.640 0.362 0.349 0.706 0.410 0.499 0.529 0.489
0.494 0.87 1.5 3.267 0.291 0.514 0.440 0.668 0.316 0.291 0.697 0.396 0.469 0.513 0.504
0.334 0.62 1.5 2.338 0.363 0.610 0.461 0.575 0.436 0.443 0.731 0.425 0.537 0.549 0.436
0.408 0.71 1.5 2.672 0.332 0.565 0.452 0.606 0.386 0.380 0.716 0.413 0.507 0.532 0.478
0.494 0.81 1.5 3.033 0.291 0.513 0.440 0.637 0.329 0.310 0.704 0.396 0.469 0.513 0.508
0.558 0.88 1.5 3.288 0.257 0.475 0.430 0.659 0.288 0.259 0.696 0.381 0.441 0.499 0.532
0.389 0.65 1.5 2.421 0.341 0.576 0.454 0.576 0.408 0.409 0.727 0.417 0.515 0.537 0.453
0.466 0.73 1.5 2.730 0.305 0.531 0.444 0.603 0.359 0.348 0.714 0.402 0.482 0.520 0.502
0.541 0.80 1.5 3.015 0.267 0.486 0.433 0.627 0.311 0.289 0.704 0.385 0.448 0.503 0.501
0.632 0.89 1.5 3.344 0.216 0.431 0.420 0.653 0.255 0.219 0.695 0.362 0.408 0.483 0.545
0.608 0.86 1.5 5.357 0.230 0.445 0.423 0.641 0.272 0.241 0.698 0.368 0.418 0.488 0.689
0.684 0.86 1.5 5.357 0.186 0.400 0.413 0.627 0.241 0.205 0.698 0.347 0.384 0.471 0.6060.334 0.89 1.5 4.167 0.363 0.609 0.461 0.705 0.377 0.363 0.695 0.425 0.537 0.549 0.504
0.376 0.89 1.5 4.167 0.346 0.584 0.456 0.698 0.360 0.343 0.695 0.419 0.520 0.539 0.511
0.100 0.91 1.5 3.409 0.426 0.750 0.483 0.758 0.469 0.469 0.693 0.448 0.603 0.601 0.537
0.126 0.91 1.5 3.409 0.422 0.735 0.481 0.753 0.458 0.457 0.693 0.447 0.599 0.595 0.538
0.156 0.91 1.5 3.409 0.416 0.716 0.479 0.747 0.446 0.442 0.693 0.445 0.593 0.588 0.546
0.217 0.91 1.5 3.409 0.402 0.680 0.474 0.736 0.421 0.413 0.693 0.440 0.577 0.575 0.564
0.280 0.91 1.5 3.409 0.383 0.642 0.468 0.725 0.395 0.383 0.693 0.433 0.557 0.561 0.583
0.342 0.91 1.5 3.409 0.360 0.605 0.460 0.714 0.370 0.353 0.693 0.424 0.534 0.547 0.582
Fig. 10. Comparison of present results with those of Singh et al. [7] and Borghei
et al. [9] when L/b = 0.50.Fig. 11. Comparison of recent results with those of Singh et al. [7] and Borghei
et al. [9] when L/b = 3.00.
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Table 5
Comparison of present results with those in the literature when L/b = 3.0.F1 p/h1 L/b L/h1 Subramanya
and
Awasty [2]
Ranga
Raju
et al. [4]
Hager [5] Singh
et al. [7]
Jalili
and
Borghei[8]
Borghei
et al. [9]
Swamee
etal. [10]
Cheong [6] Nandesamoorthy
and
Thomson [1]
Yu-
Tech [3]
Present
study
0.282 0.82 3.0 10.266 0.382 0.641 0.467 0.682 0.414 0.498 0.702 0.432 0.556 0.560 0.608
0.328 0.79 3.0 9.824 0.366 0.614 0.462 0.656 0.403 0.487 0.706 0.426 0.539 0.550 0.585
0.369 0.78 3.0 9.720 0.350 0.589 0.457 0.645 0.388 0.470 0.707 0.420 0.523 0.541 0.602
0.405 0.83 3.0 10.356 0.334 0.567 0.452 0.663 0.361 0.437 0.701 0.414 0.508 0.533 0.6760.473 0.84 3.0 10.492 0.302 0.527 0.443 0.656 0.332 0.401 0.700 0.401 0.479 0.518 0.932
0.495 0.80 3.0 9.974 0.291 0.513 0.439 0.632 0.332 0.403 0.705 0.396 0.469 0.513 0.672
0.507 0.81 3.0 10.184 0.284 0.506 0.438 0.638 0.323 0.392 0.703 0.393 0.463 0.510 0.7010.637 0.80 3.0 7.487 0.213 0.428 0.419 0.607 0.273 0.334 0.705 0.360 0.405 0.482 0.834
0.786 0.79 3.0 7.448 0.126 0.339 0.400 0.578 0.213 0.265 0.705 0.314 0.340 0.449 1.0660.826 0.79 3.0 7.361 0.102 0.314 0.395 0.566 0.199 0.248 0.706 0.299 0.322 0.440 1.116
0.807 0.80 3.0 7.509 0.114 0.326 0.397 0.577 0.203 0.252 0.705 0.306 0.331 0.444 1.148
0.652 0.79 3.0 7.445 0.205 0.419 0.417 0.602 0.268 0.329 0.705 0.356 0.398 0.478 0.841
0.485 0.72 3.0 6.730 0.296 0.519 0.441 0.594 0.353 0.432 0.715 0.398 0.473 0.515 0.618
0.440 0.73 3.0 6.821 0.318 0.546 0.447 0.607 0.369 0.450 0.714 0.407 0.493 0.525 0.609
0.389 0.75 3.0 7.031 0.341 0.577 0.454 0.627 0.386 0.468 0.711 0.417 0.515 0.537 0.600
0.343 0.78 3.0 7.335 0.360 0.605 0.460 0.652 0.397 0.481 0.707 0.424 0.533 0.547 0.628
0.284 0.81 3.0 7.619 0.382 0.640 0.467 0.677 0.415 0.500 0.703 0.432 0.556 0.560 0.6390.236 0.85 3.0 7.980 0.397 0.668 0.472 0.705 0.426 0.511 0.699 0.438 0.571 0.571 0.697
0.181 0.90 3.0 6.713 0.411 0.701 0.477 0.736 0.439 0.524 0.695 0.443 0.587 0.583 0.6820.221 0.84 3.0 6.305 0.401 0.678 0.474 0.702 0.435 0.522 0.700 0.439 0.576 0.574 0.592
0.263 0.81 3.0 6.092 0.389 0.652 0.470 0.681 0.423 0.510 0.703 0.435 0.562 0.565 0.576
0.307 0.90 3.0 6.761 0.374 0.626 0.465 0.716 0.386 0.462 0.694 0.429 0.547 0.555 0.770
0.411 0.84 3.0 6.267 0.331 0.564 0.451 0.666 0.358 0.432 0.701 0.413 0.506 0.532 0.690
0.435 0.72 3.0 5.379 0.320 0.549 0.448 0.603 0.374 0.456 0.715 0.408 0.495 0.526 0.544
0.615 0.90 3.0 6.774 0.226 0.441 0.422 0.662 0.259 0.314 0.694 0.367 0.415 0.487 1.020
0.679 0.90 3.0 6.784 0.189 0.403 0.414 0.651 0.233 0.283 0.694 0.348 0.387 0.472 1.160
0.651 0.88 3.0 6.604 0.205 0.419 0.417 0.644 0.249 0.303 0.696 0.356 0.399 0.478 1.009
0.703 0.88 3.0 6.575 0.175 0.388 0.410 0.633 0.229 0.279 0.696 0.341 0.376 0.467 1.020
0.735 0.90 3.0 6.773 0.156 0.369 0.406 0.640 0.210 0.256 0.694 0.331 0.362 0.460 1.3470.808 0.91 3.0 6.813 0.113 0.325 0.397 0.630 0.179 0.220 0.693 0.306 0.330 0.444 1.746
0.769 0.88 3.0 6.591 0.136 0.348 0.402 0.622 0.201 0.247 0.696 0.319 0.347 0.452 1.2880.244 0.86 3.0 10.714 0.395 0.664 0.472 0.706 0.421 0.506 0.698 0.437 0.569 0.569 0.677
0.367 0.86 3.0 10.714 0.350 0.590 0.457 0.684 0.371 0.447 0.698 0.420 0.524 0.542 0.722
0.797 0.86 3.0 10.714 0.294 0.517 0.440 0.662 0.322 0.389 0.698 0.397 0.472 0.515 0.792
0.715 0.89 3.0 8.333 0.168 0.381 0.409 0.637 0.221 0.270 0.695 0.337 0.371 0.464 1.347
0.750 0.89 3.0 8.333 0.147 0.360 0.404 0.631 0.207 0.253 0.695 0.326 0.355 0.456 1.556
0.165 0.91 3.0 6.818 0.415 0.711 0.479 0.746 0.443 0.528 0.693 0.444 0.591 0.586 0.731
0.277 0.91 3.0 6.818 0.384 0.644 0.468 0.726 0.397 0.474 0.693 0.433 0.558 0.562 0.785
0.397 0.75 3.0 9.375 0.337 0.572 0.453 0.626 0.382 0.464 0.711 0.415 0.511 0.535 0.5830.550 0.75 3.0 9.375 0.262 0.480 0.432 0.599 0.320 0.391 0.711 0.383 0.444 0.501 0.682
0.610 0.80 3.0 7.500 0.228 0.444 0.423 0.612 0.284 0.347 0.705 0.368 0.417 0.487 0.8570.679 0.80 3.0 7.500 0.189 0.403 0.414 0.600 0.256 0.314 0.705 0.348 0.387 0.472 0.914
0.246 0.83 3.0 6.250 0.394 0.663 0.471 0.694 0.426 0.512 0.701 0.437 0.568 0.569 0.6000.328 0.83 3.0 6.250 0.366 0.614 0.462 0.679 0.392 0.473 0.701 0.426 0.539 0.550 0.656
0.434 0.83 3.0 6.250 0.320 0.550 0.448 0.660 0.349 0.422 0.701 0.408 0.496 0.527 0.674
when L/b = 3. An equation predicting the discharge coefficientof rectangular sharp-crested side weirs was developed. The
presented equation for Cd, De Marchis coefficient is reliable in
subcritical flow conditions. Thus, the discharge coefficient derived
from the equation can be used with confidence.
Acknowledgments
The authors are grateful for the constructive comments of
various anonymous reviewers, which strengthened and further
focused the manuscript. The authors acknowledge the financial
support of the Scientific and Technological Research Council of
Turkey (TUBITAK) under Project No. MAG 104M394.
References
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http://dx.doi.org/doi:10.1016/j.flowmeasinst.2010.11.002http://dx.doi.org/doi:10.1016/j.flowmeasinst.2010.11.002http://dx.doi.org/doi:10.1016/j.flowmeasinst.2010.11.002