Environmental Engineering Reference
In-Depth Information
Converging
inlet
Diverging
outlet
hroat
Flow
Top view
Stilling well for
measuring head
figure 2.36 Parshall flume.
The most common flume used for a permanent wastewater flow-
metering installation is called the
Parshall flume.
, shown in Figure 2.36.
Formulas for flow through Parshall flumes differ, depending on throat
width. The formula below can be used for widths of 1 to 8 ft and applies
to a medium range of flows:
152
.
.
026
qWhW
a
=× ×
4
×
(2.29)
where:
q
= flow.
W
= width of throat.
h
a
= depth in stilling well upstream.
Note:
Parshall flumes are low-maintenance items.
2.14 ChaPTer revieW QuesTions
2.1
What should be the minimum weir height for measuring a flow of
900 gpm with a 90° V-notch weir, if the flow is now moving at 3
ft/s in a 2-ft-wide rectangular channel?
2.2
A 90° V-notch weir is to be installed in a 30-in.-diameter sewer to
measure 600 gpm. What head should be expected?
2.3
For dirty water operations, a
or
orifice
plate should be used.
2.4
A
has a smooth entry and sharp exit.
2.5
send a beam of ultrasonic sound waves through the
water to another transducer on the opposite side of the unit.
2.6
Find the number of gallons in a storage tank that has a volume of
660 ft
3
.
2.7
Suppose a rock weighs 160 lb in air and 125 lb under water. What
is the specific gravity?
2.8
A 110-ft-diameter cylindrical tank contains 1.6 MG water. What is
the water depth?
