UFC 4-150-06
12 December 2001
where lc
=
channel length [ft]
f lc
ken + kex +
=
Fc
4R
entrance-loss coefficient (≈ 0.1)
=
ken
exit-loss coefficient (≈ 1.0)
kex
=
Darcy-Weisbach friction factor (≈ 0.03)
f
=
R
=
hydraulic radius of inlet channel [ft]
(water-level) gradient.
Since the entrance is constrictive, the amplitude of the bay tide will differ from the
amplitude of the tide range in the ocean. The bay-tide amplitude can be determined
from the following relationship:
ab
=ε
(5-6)
as
=
dimensionless factor which depends on the
where
ε
coefficients K1 and K2
(see Figure 5-14)
ab
=
range of bay tide [ft]
Note that for small values of K1, which denotes large inertia forces, the value of ε is
greater than one.
For irregular entrance channels, an effective channel length, lc', can be used in place of
lc.
2
R Ac
n
lc' = ∑ ∆ Xn
(5-7)
i Rn An
where:
=
average hydraulic radius of channel [ft]
R
2
=
average cross section of channel at mean tide level [ft ]
Ac
hydraulic radius at each of n sections of equal length, ∆Xn , [ft]
=
Rn
2
cross section of channel at each of n sections of length, ∆Xn , [ft ]
=
An
This analysis provides an estimate of the channel-inlet hydraulics applicable to design
situations. However, if the assumptions in paragraph 5.5.1.3a are not satisfied, or if the
current velocities are critical to the channel design, a more detailed analysis to include
mathematical or physical-model simulation is necessary.
5-26
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