ASA 128th Meeting - Austin, Texas - 1994 Nov 28 .. Dec 02

5aEA7. Theoretical evaluation of flow-induced noise in hull-mounted sonar arrays.

Bertrand Dubus

Inst. d'Electron. et de Microelectron. du Nord, UMR CNRS 9929, Dept. ISEN, 41 boulevard Vauban, 59046 Lille Cedex, France

Christian Giangreco

DCN-Ingenierie Sud, DLSM, Le Brusc, 83140 Six Fours les Plages, France

Future hull-mounted sonar arrays are likely to be limited by the effects of flow-induced acoustic noise on the sensors. These arrays are usually constituted by extended sensors embedded in an elastomer layer acting as outer decoupler (OD) mounted on a structural support plate (SSP). Predictive models of flow-induced noise are obtained by assuming specific mechanisms: (i) The direct path results from the detection by the sensors of the fluctuating pressures from the turbulent boundary layer after propagation through the OD [Ko et al., J. Acoust. Soc. Am. 85, 1469 (1989)]; (ii) the flexural noise is associated with the flexure of the extended sensors via their lateral sensitivity [Montgomery et al., J. Acoust. Soc. Am. 94, 1688 (1993)]; (iii) The vibrating SSP radiates acoustic pressures in the near field which are sensed by the array. The OD and SSP are assumed of infinite extent for the direct path and of finite extent otherwise. This paper presents an analytical model for the later path. Results are displayed in terms of wave-number-frequency spectrum of the radiated pressure and of frequency spectral density. The relative contribution of the different paths and the effect of various parameters of the array are discussed.