H Flumes, P-40 = 3
( as developed by the U.S.Department of Agriculture, Soil Conservation Service )
» sized by max depth of flume, D. Enter value ( in units of P-1 ) into P-43.
» approach is preferably rectangular, matching width and depth for
distance 3 to 5 times the depth of the flume
» flow range 100 : 1
» may be installed in channels under partial submergence
( ratio of downstream level to head ).
Typically: » 1% error @ 30% submergence
» 3% error @ 50% submergence
» for rated flows under free flow conditions, the head is measured at a
point downstream for the flume entrance.
» H flumes come with a flat or sloping floor.
The same flow table can be used as error is less than 1%.
» position the transducer such that it is centered over the flow at a
minimum height of 30 cm ( 12" ) above the maximum head.
transducer
point of
measurement
side
front
plan
D
Q
Flume Size Point of Measurement
( D ft ) cm inches
0.5 5 1
3
/
4
0.75 7 2
3
/
4
1.0 9 3
3
/
4
1.5 14 5
1
/
2
2.0 18 7
1
/
4
2.5 23 9
3.0 28 10
3
/
4
4.5 41 16
1
/
4
PL-443 6 – 38
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