Mooring Loads Due to Parallel Passing Ships - State Lands ...

Facility and Test Rigs
The study required testing in shallow water in a wide towing tank, in order to
minimize side wall effects. The existing towing tanks at the Naval Academy were too
narrow or could not be used with shallow water depths, so tests were conducted in the
wider Coastal Engineering basin instead. The tests section of the coastal engineering
basin is rectangular, and is 40 ft long and 18 ft wide. Water depths are adjustable and
ranged from 4.1 inches to 14.5 inches.
The tank did not have towing capability, so a new towing system was designed
and constructed for this project. The towing rig consisted of an aluminum frame that
spanned the entire 40 ft length of the basin, a closed-loop cable drive system, a towing
carriage (attached to the drive cable) that rolled along the frame, and a variable speed
drive motor. The “passing ship” model was attached under the towing carriage by
means of a heave post and pitch pivot that allowed the model to move vertically as the
water level was changed from run to run and to achieve realistic squat and trim during
model tests. Figure 2 gives an overview of the towing rig in the basin while Figures 3a
and 3b show views of the towing carriage with the passing ship attached.
Figure 2. View of Coastal Engineering Basin with moored ship in foreground
and passing ship in background. Passing ship is attached to towing carriage
that rolls along aluminum frame.
NFESC TR-6056-OCN
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