Recent Work at the NUWC/NASA Langley Seawater Tow Tank

Abstract

The Langley seawater tow tank, located on Langley Airbase in Hampton, Virginia, was designed and built by NACA in 1931 for seaplane research and has been in various states of use since then. Since 1983, NUWC has maintained stewardship of the tank and has conducted a large number of tests there. This paper will present an overview of the facility and its capabilities as well as discuss several recent test results. The tank is reinforced concrete, 2880 feet long, 12 feet deep, and 24 feet wide, and can be filled with 5.4 million gallons of either fresh or baywater. Baywater can be filtered to 25 microns and has a salinity about half that of seawater. The carriage is powered by eight 75 hp D.C. motors with trolley style cables and can attain speeds of up to 40 knots. Power is generated by a 850 kW motor generator. Several struts exist for model towing and the carriage bas 110/120 V.A.C. and 3 phase 208 A.C. volt available power. A workshop is in the building and a variety of instrumentation and data acquisition is on hand. Unique possibilities exist at the LTT due to the organic and physical properties of seawater. For example, one of the largest ever artificial colonies of plankton was grown there. Furthermore, because of the electrical conductivity of the water, research into the control of turbulent flows by magnetohydrodynamic forces can be, and bas been, performed there. To illustrate the variety of test configurations an capabilities, results are presented from three recent test programs performed at the tank. The first will be the set-up and test results of a fully submerged axisymmetric 180 inch long cylindrical sting mounted model. The test rig will be shown including the floating swing balance which is coupled to an axial load cell. Test results will be shown for hydrodynamic resistance versus speed at zero and non-zero attack angles. The second set of results shown will be those of a towed cylindrical body equipped with remotely actuated hydrodynamic drag brakes which was released in flight an allowed to come to rest Drag measurements made at different drag brake settings and speeds will be presented as well as photographic documentation. Finally, a recent set of test results will be presented; taken on a submerged cylindrical body, strut mounted to a 6 degree of freedom load balance. Results to be presented will include force and moment measurements as a function of speed and attack angle.