UFC 4-150-06
12 December 2001
freshwater inflow is minimal, and
the ocean tide is approximately sinusoidal, then a good approximation for
the current velocity is
2 π as Ab
(5-2)
Vm =
Ac T
=
average cross-section velocity at
where Vm
maximum tidal flow [ft/sec]
T
=
period of tide [sec]
Ab
=
surface area of basin [ft2]
=
cross section of opening at mean tide
Ac
level [ft2]
as
=
range of the ocean tide [ft]
The circumstance that the entrance is not constrictive, together with the condition in
Equation 5-1, imply that the water surface in the bay fluctuates uniformly and equals the
ocean tide.
5-6.1.3.2
If the entrance is constrictive, as shown in Figure 5-12, it reduces the tide
range in the bay, so the above expression will overestimate the tidal currents. If
conditions outlined in (1) are satisfied, the maximum current in the entrance can be
determined from this equation:
2π as Ab e
(5-3)
Vm =
Ac T
Vm = average cross-section velocity at maximum tidal flow
where
[ft/sec]
2
Ac
=
cross section of opening at mean tide level [ft ]
T
=
period of tide [sec]
=
range of the ocean tide [ft]
as
e
=
dimensionless factor which depends on
coefficients K1 and K2;
see Figure 5-13.
The coefficients K1 and K2 are defined as follows:
(5-4)
as Ab Fc
K1 =
2 lb Ac
2 π lc Ab
(5-5)
K2 =
T g Ac
5-25
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