Environmental Engineering Reference
In-Depth Information
Table 4.8. Variables for different structures and flow conditions.
Structure
Flow condition
µ
h
h
Broad-crested
Free
1
2/3
H
1
H
1
/3
Submerged
0.7
H
1
H
1
-
H
2
Flume
Free
1
2/3
H
1
H
1
/3
Submerged
0.8
H
1
H
1
-
H
2
Short-crested
Free
1
2/3
H
1
H
1
/3
Submerged
0.2
H
1
H
1
-
H
2
Sharp-crested
Free
1
2/3
H
1
H
1
Submerged
1
H
1
H
1
-
H
2
Undershot
Free
1
a
h
1
-C
1
a
Submerged
1
a
h
1
-
h
2
where:
H
1
=
upstream energy head above the crest (m)
H
2
=
downstream energy head above the crest (m)
h
1
=
upstream water depth (m)
h
2
=
downstream water depth (m)
C
1
=
contraction coefficient
a
=
gate opening (m)
Table 4.9.
Discharge coefficient
C
.
Coefficient
C
Structure
Type of structure/crest
Minimum
Maximum
Broad-crested weir
Rounded upstream face of crest
0.930
1.02
Sharp upstream face of crest
0.848
1.12
Flume
RBC
0.930
1.02
Short-crested weir
WES weir
0.750
Sharda type fall (trapezoidal crest)
0.675
Sharp-crested weir
0.611
1.06
Undershot
0.510
0.70
Table 4.10. Variables for undershot structures.
Undershot structure
h
h
Free flow
a
h
1
−
C
c
a
Submerged
a
h
1
−
h
2
where:
h
1
=
upstream water depth (m)
h
2
=
downstream water depth (m)
contraction coefficient
a
=
gate opening (m)
C
c
=
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