ASA 126th Meeting Denver 1993 October 4-8

4aEA4. Application of multilayered structure for flow noise reduction.

Sung H. Ko

Naval Undersea Warfare Ctr. Detachment, New London, CT 06320

Turbulent boundary layer pressure fluctuations can be reduced by filtering of its wave-number response with either a finite hydrophone or a hydrophone array, or by filtering the wave-number response through a layer (layers) of elastomer. The elastomer layer is frequently called an outer decoupler and the multilayered structure is a generalized outer decoupler. In general practice, hydrophone arrays are embedded within the outer decoupler to reduce the turbulent boundary layer pressure fluctuations and then mounted to an elastic structure. The analysis of a multilayered structure is presented here to evaluate the transfer function, which is a measure of wave-number filtering through an outer decoupler. The front of the first layer is exposed to turbulent flow and the back of the last layer is in contact with static air. The results presented here are the numerically calculated transfer functions and noise reductions achieved by various layers of elastomer mounted on a steel plate.