ASA 127th Meeting M.I.T. 1994 June 6-10

2pSA9. Virtual sources, guided wave paths, and far-field radiation from an internally excited ribbed cylinder.

Joseph A. Clark

Michael A. Sartori

Code 734, Carderock Div., Naval Surface Warfare Ctr., Bethesda, MD 20084-5000

An experimental analysis of structural dynamics and acoustic radiation associated with a large scale (7.5 m long, 1.5 m diam) immersed hull structure is presented. Pressure data were collected with an automated scanning frame and an array of hydrophones at 0.3-m intervals over a measurement surface conformal to and 0.3 m distant from the body. Visualizations of the pressure field in the measurement plane were analyzed to verify data quality and to characterize dominant phenomena (hull resonances, low-order mode shapes, virtual source locations, and scattering discontinuities). The data were then backprojected to the hull using near-field acoustical holography algorithms to obtain (normalized) pressure, velocity, and intensity distributions on the hull. Finally, algorithms based on the Helmholtz integral were employed to determine far-field radiation patterns. [Work sponsored by NAVSEA.]