N101-098 TITLE: Skin Friction Measurement Technology for Underwater Applications

TECHNOLOGY AREAS: Ground/Sea Vehicles, Battlespace, Nuclear Technology

OBJECTIVE: Develop a self-contained skin-friction measurement gauge.

DESCRIPTION: For design, the resistance is a key component in arriving at a viable propulsion system. For example, the friction drag of ships can, at least in principle, be reduced by the use of some form of lubrication at the hull-water interface. Efforts to explore that possibility are hindered by, inter alia, the lack of a means of making direct measurements of friction drag at points on the hull�s surface. The objective here is to provide a means to design a gauge that will remedy this deficiency. The shear stress device should be flush with the hull.

PHASE I: Proof of concept demonstration with variations in Reynolds numbers (as high as 1 million) in a water channel/tunnel for a near-wall turbulence measurement system. For the shear-stress device, the contractor is expected to devise an instrument, and to produce a quantitative analytic description of its performance characteristics, that can be implemented in the form of an insert whose outer surface is flush with the hull and is of approximate dimensions 25 mm in length and 12 mm in width. It must be watertight, and able to withstand pressures of as much as 10 atmospheres. There must be no moving parts except for the strain needed to produce a change in the physical property used to effect the sensing. It is expected that the accuracy would be � 1% or better and that the output would be a digitized sampled data stream.

PHASE II: For near-wall measurements, the contractor will develop and demonstrate the turbulence measurement system at high Reynolds numbers (10 million) on a flat plate in a water tunnel/channel and compare results with analytical theory of turbulence, providing mean and unsteady velocities to within 2-5 microns of the surface. For the shear-stress device, the contractor is expected to construct a prototype and demonstrate its properties in a (small) water tunnel.

PHASE III: For the near-wall measurement system, the contractor will prepare complete system and user-documentation. For the shear-stress device, it is expected that a successful result will be implemented in a large-scale high-speed measurement program aimed at fully characterizing the merits of various techniques of friction drag reduction.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: Resistance measurement systems are useful to both air and underwater application communities. This system would provide the unique capability for the commercial and military aircraft, submarine, and ship industries.

REFERENCES:
1. Naughton, J. W., Sheplak, M. (2002) Modern developments in shear-stress measurements. Progress in Aerospace Sciences, Vol. 38, pp. 515-570.

2. Bennett, M.D., Leo, D.J. (2003) Manufacture and characterization of ionic polymer transducers employing non-precious metal electrodes. Smart Materials and Structures, Vol. 12, pp. 424-436.

KEYWORDS: turbulence; hydromechanics; underwater measurements; diagnostics; skin-friction; shear stress.

** TOPIC AUTHOR (TPOC) **

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