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21.1.6 Add a "Flowrate (Weir)" channel type
The HydroMace 3000 contains in-built equations for allowing users to measure
flow rate through rated structures such as flumes and weirs. The table below lists
the structures supported and the equations used to calculate flow rate.
All of the weir equations assume that the flow is fully contracted, meaning that
the approach channel is wide enough and deep enough that the proximity of
the floor and sidewalls to the weir opening does not affect the flow (Tony L. Wahl,
Bureau of Reclamation Hydraulics Laboratory in Denver, Colorado, USA).
The equations used by the HydroMace 3000 and reproduced here are used
with permission of U.S. Dept. of the Interior, Bureau of Reclamation - Hydraulic
Investigations and Laboratory Services Group. For further information users are
encouraged to visit the following websites:
www.usbr.gov/pmts/hydraulics_lab/pubs/wmm/index.htm
www2.alterra.wur.nl/Internet/webdocs/ilri-publicaties/publicaties/Pub20/pub20.pdf
Flume and Weir equation Summary
equation, cfs (head measured in feet)
Contracted rectangular weir
Q=3.33(L-0.2h
Suppressed rectangular weir Q=3.33(L)h
V-notch weir, 90°
Q=2.49h
V-notch weir, 30°
Q=(8/15)(2g)
V-notch weir, 45°
Q=(8/15)(2g)
V-notch weir, 60°
Q=(8/15)(2g)
Cipoletti weir
Q=3.367(L)h
parshall flumes
Q=Ch
n
a
replogle flumes
Q = K
(h
1
(long-throated flumes or
"ramp" flumes)
palmer-Bowlus flumes
Q = K
(h
1
Definitions, cfs
Q = discharge, cfs
L = weir width, ft
h
= upstream head, ft
1
C
= V-notch weir coefficient
e
k
= V-notch weir head adjustment factor, ft
h
θ = V-notch weir angle, degrees
h
= Parshall flume upstream head, ft
a
C = Parshall flume coefficient
n = Parshall flume exponent
g = acceleration due to gravity, 32.2 ft/s
2
the V-notch weir and parshall flume coefficients used by the hM 3000 can be found in appendix a
42
SeCtion b SoFtware Manual
equation, kL/sec (m
measured in meters
)h
1.5
Q=1.84(L-0.2h
)h
1.5
1
1
1
1
1.5
Q=1.84(L)h
1.5
1
1
2.48
Q=1.34h
2.48
1
1
0.5
C
tan(θ/2)(h
+k
)2.5
Q=(8/15)(2g)
0.5
C
tan(θ/2)(h
e
1
h
e
0.5
C
tan(θ/2)(h
+k
)2.5
Q=(8/15)(2g)
0.5
C
tan(θ/2)(h
e
1
h
e
0.5
C
tan(θ/2)(h
+k
)2.5
Q=(8/15)(2g)
0.5
C
tan(θ/2)(h
e
1
h
e
1.5
Q=1.86(L)h
1.5
1
1
Q=0.552*Ch
n
a
+K
)
U
Q = K
(h
+K
)
U
1
2
1
1
2
+K
)
Q = K
(h
+K
)
U
U
1
2
1
1
2
Definitions, kL/sec
Q = discharge, kL/sec
L = weir width, m
h
= upstream head, m
1
C
= V-notch weir coefficient
e
k
= V-notch weir head adjustment factor, m
h
θ = V-notch weir angle, degrees
h
= Parshall flume upstream head, m
a
C = Parshall flume coefficient
n = Parshall flume exponent
g = acceleration due to gravity, 9.806 m/s
RetuRn to toC
1. Select the "Flowrate (using Weir)" channel type from
the "New channel" dialogue box and click "Continue".
2. The "Channel name" dialogue box will
appear. Enter a channel "Name" in to the text
field (16 character maximum). This "name" will
also be displayed on the HM 3000 main LCD if
enabled. Click "Continue".
3. In the "Select depth channel" dialogue box
use the drop down list to highlight the depth
channel from which the channel (named
"Parshall" in this example) will receive its value.
Click "Continue" and the "Select weir type"
/sec) ~ head
3
dialogue box will appear.
4. Select the weir type that you
wish to configure. If you are setting
up a flow rate through a Parshall
+k
)2.5
1
h
flume, expand the "Parshall
+k
)2.5
1
h
flume" weir type and select the
+k
)2.5
1
h
appropriate flume width from the
expanded list.
5. Click "Continue" to complete the new channel.
6. The "Configure channels" dialogue box will re-appear with the new
channel listed.
2
RetuRn to toC
MaCe HydRoMaCe 3000 Product Manual
43
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