380 foot Towing Tank

Large models can vastly improve full scale predictions made from certain types of model tests. Ship models up to 25 feet in length can be tested in the Laboratory's 380 foot towing tank. This tank is equipped with two towing carriages, a dual flap wavemaker, a planar motion mechanism for maneuvering experiments, fans for simulating over-water winds, and has a high speed test towing capability. A drydock allows the set-up of underwater (submarine) experiments while the tank is in use for other tests. A host computer facility is contained within the control room. The computer is used to control the wavemakers and is used to process data. Control signals and data are transmitted between the carriage and the control room by a fiber optic cable system. Additionally, a self contained computer workstation on the towing carriage can be used to acquire and analyze experimental data.

This facility has been used to test a wide variety of models, including: ships, submarines, hydrofoils and surface effect craft, planing boats, SWATH's, sailboats, offshore platforms, wave buoys, divers, mine arrays, pilings, etc. It is also used to study wave motions and forces, without the use of models.

Length = 380 ft
Breadth = 26 ft
Depth of Water = 16 ft
Drydock Length = 34 ft

FFG-7 in Wind and Waves	Breaking Waves

DESCRIPTION OF CARRIAGE:

1) high speed - box girder, supported on round way bearings or rulon slippers

2) low speed - supported on round way bearings (towed by high speed carriage)

TYPE OF DRIVE SYSTEM AND TOTAL POWER:

twin cables attached to high speed carriage, 2 - 150 kw D.C. motors (400% overload capability) = 1600HP

OTHER CAPABILITIES:

large amplitude planar motion mechanism

four centrifugal fans for generating over-water winds of up to ? ft/sec

WAVE GENERATION CAPABILITY:

regular, irregular, and transient water waves, wave frequency range 0.25 to 1.25 Hz

WAVEMAKER TYPE:

dual flap servo-hydraulic control, manufactured by MTS

BEACH TYPE AND LENGTH:

4 layer of rectangular bars, 60 ft long at 1-to-3 slope

INSTRUMENTATION:

fiber optic telemetry system between carriage and shore to transmit digital data, t.v., and control channels, 15 bit A/D converters on each carriage and on shore, modular variable reluctance force blocks for all force measurements, variable torque and thrust dynamometers, planing boat and S.E.S dynamometer, 3 axis submerged model dynamometer, open water propeller dynamometers, rudder torque gauges, ultransonic and resistance wave height gauges, acoustic doppler velocimeters

TESTS PERFORMED:

resistance in self-propulsion in calm water and waves, seakeeping tests, open water propeller test, 3-D wake surveys, horizontal planar motion tests, various tests of fixed and floating ocean structures, hydrodynamic forces on submerged bodies, foils, etc., capsize and dynamic stability tests, flow visualization, basic ocean wave mechanics

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