Environmental Engineering Reference
In-Depth Information
Short Exercise 5: Calibration of Weir Coefficient
V-notch weirs provide stable and reliable flow measurements, particularly when the
coefficient
C
in the weir formula (Eq.
3.28
) is determined to reflect site-specific
conditions. Table
3.6
lists measurements of water level (
h
) and discharge (
Q
) for the
V-notch weir shown in Fig.
3.11b
. The water level is measured with respect to the
base of the weir. Therefore,
h
0
¼
0inEq.
3.28
.
1. Compute
h
5/2
and convert
Q
to m
3
s
1
.
2. Plot
h
5/2
and
Q
in the graph and determine the slope of the plot.
3. Determine
C
in Eq.
3.28
. Note that
θ ¼
90
; thus, tan(
θ
¼
/2)
1. Compare this
value to the theoretical value for an ideal weir,
C
¼
1.38.
