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V-notch angle weirs, the head is measured upstream of the weir plate at a
minimum distance of 3 times maximum head to ensure the surface of the
liquid is not effected by turbulence or drawdown. See Exponential devices,
above, for further details.
Calculations
Palmer Bowlus Flume and H-Flume
ABSOLUTE
If the flow calculation is to be absolute P702 = 1 the flow will be calculated
using the formula: q = f(h)
Where: q = flowrate
f = is an 8
th
degree polynomial solution for h (head)
RATIOMETRIC
If the flow calculation is to be ratiometric P702 = 2 the flow will be
calculated using the formula: q= q
cal
f(h)/f(h
cal
)
Where: q = flowrate
q
cal
= flowrate at maximum head P705
f(h) = a polynomial solution for h (head)
f(h
cal
) = a polynomial solution for h
cal
(maximum head)
V-Notch Angle Weir (Non-BS 3680)
ABSOLUTE
If the flow calculation is to be absolute P702 = 1 the flow will be calculated
using the formula: q = C
e
8/15 tan (theta/2)(2gn)
0.5
(h = kh)
2.5
Where: q = flowrate
C
e
= discharge coefficient calculated by the Flow 5 P723
theta = V-notch angle
gn = gravitational acceleration
h = head
kh = compensated head
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