Flow noise reduction techniques for a planar array of hydrophones

Abstract

This paper presents techniques for reducing turbulent boundary layer pressure fluctuations using wave-number filters. Reduction of flow noise can be achieved by filtering wave numbers using a finite hydrophone or an array of hydrophones, or by filtering wave numbers using a layer of elastomer. The baseline turbulent wall pressure spectrum that represents the flow excitation function is based on the Corcos model modified to fit a realistic estimate at the low wave-number region. The occurrence of the convective ridge wave number is estimated by using a convective flow speed that is a function of frequency. Major results presented are numerically calculated noise reductions compared to the calculated noise level for a flush-mounted point hydrophone.