The Naval Auxiliary Air Station, Whiting Field, is to have a stormwater
disposal system in which the existing pipes and terraces under
and in the vicinity of the runways and building area will discharge
into paved trapezoidal open channels. Many of the channels join other
channels as they pass down the sides of the plateau on which the airfield is located. The grades of the main channels and of many of the
lateral channels are such that water flows at supercritical velocities
or at velocities greater than that of a gravity wave. The
difficulties anticipated in joining two streams of water, one or more
of which is flowing at supercritical velocities, led to the request for
model studies of several of the channel junctions.
The primary objectives in the present study include (1) the development
of junction designs for specified operating conditions which
would result in reasonably smooth flow downstream of the junction and
(2) the determination of the necessary wall heights in the vicinity of
the junction. Economic and structural considerations involved in the
junction designs were considered in the final selection.
Dependent upon the junction design, the discharges, velocities,
and related phenomena of the flow in the vicinity of the junction, a
hydraulic jump may form in one or both of the inlet channels. This may
necessitate a large increase in the height of the sidewalls in the
vicinity of the junction. On the other hand, if the flow passes through
the junction at velocities greater than the critical, standing waves
may form which have a height greatly in excess of a normal freeboard
and which continue to oscillate back and forth across the channel for
a considerable distance downstream from the junction before being damped
by frictional forces. These standing waves necessitate higher sidewalls
not only in the vicinity of the junction but for a considerable distance
downstream. As available information on junctions of this type
is almost nonexistent, it was necessary to resort to model studies in
order to determine the flow conditions and the minimum sidewall heights.
Two general types of junctions were studied. One type consists
of the junction of two large channels in which the lateral and inlet
main have comparable discharges. The other type, called terrace outlets,
consists of a junction between a main channel and a terrace channel
having a relatively small discharge.
The maximum discharge ranges from 380 to 960 cfs in the main channels
and from 25 to 70 cfs in the terrace channels. The maximum velocity
of flow encountered is approximately 30 fps.
Bowers, Charles E..
Hydraulic Model Studies for Whiting Field Naval Air Station.
St. Anthony Falls Hydraulic Laboratory.
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