Environmental Engineering Reference
In-Depth Information
Table 2.4.
Flow types based on the energy line, bottom slope and Froude number.
Actual water depth
y
Relation energy line and
in relation to
y
n
bottom slope
Flow type
S
f
< S
o
or
S
o
−
S
f
>
0
y > y
n
Gradually varied
y
=
y
n
S
f
=
S
o
or
S
o
−
S
f
=
0
Uniform
y < y
n
S
f
> S
o
or
S
o
−
S
f
<
0
Gradually varied
Actual water depth
y
in relation to
y
c
Froude number
Flow type
Fr
2
<
1or1
Fr
2
>
0
y > y
c
−
Subcritical
Fr
2
Fr
2
y
=
y
c
=
1or1
−
=
0
Critical
Fr
2
>
1or1
Fr
2
>
0
y < y
c
−
Supercritical
Another classification of flow types is based on the type of slope and
the actual water depth. Table 2.5 gives a summary of the most common
water surface profiles in wide canals; a graphical presentation of these
profiles is given in Figure 2.12. Figure 2.13 gives an overview of the
most common water surface profiles in wide canals. These canals are
characterised by a large width
B
so that the hydraulic radius
R
is equal to
y
and the normal and the critical water depth are a function of the specific
discharge
q
=
Q/B
and the bottom roughness only.
Table 2.5.
Summary of water surface profiles.
Water surface profile
Depth range of
y
,
y
c
and
y
n
Type of
Bottom slope
1
2
3
Region 1
Region 2
Region 3
curve
Flow type
Steep S
S1
y > y
c
> y
n
Backwater
Subcritical
S
o
> S
c
S2
y
c
> y > y
n
Drawdown
Supercritical
y
n
< y
c
S3
y
c
> y
n
> y
Backwater
Supercritical
y > y
c
=
y
n
Critical C
C1
Backwater
Subcritical
S
o
=
S
c
C2
y
c
=
y
=
y
n
Uniform
Critical
y
n
=
y
c
C3
y < y
c
=
y
n
Backwater
Supercritical
Mild M
M1
y > y
n
> y
c
Backwater
Subcritical
0
< S
o
< S
c
M2
y
n
> y > y
c
Drawdown
Subcritical
y
n
> y
c
M3
y
n
> y
c
> y
Backwater
Supercritical
Horizontal H
n.a.
S
o
=
0
H2
y
n
> y > y
c
Drawdown
Subcritical
y
n
=
infinite
H3
y
n
> y
c
> y
Backwater
Supercritical
Adverse A
n.a.
S
o
<
0
A2
y > y
n
Drawdown
Subcritical
y
n
=
none
A3
y
n
> y
Backwater
Supercritical
Search WWH ::
Custom Search