The 1988 Rayleigh medal lecture: Fluid loading—The interaction between sound and vibration

• Published in: Journal of sound and vibration Vol. 133; no. 1; pp. 1 - 27
• Main Author: Crighton, D.G.
• Format: Journal Article
• Language: English
• Published: London Elsevier Ltd 22.08.1989; Elsevier
• Subjects: Acoustics; Exact sciences and technology; Fundamental areas of phenomenology (including applications); Physics; Structural acoustics and vibration; Acoustics; Vibration; Fluid structure interaction
• ISSN: 0022-460X; 1095-8568
• DOI: 10.1016/0022-460X(89)90983-8

This lecture illustrates, through simple models, in analytical and physical terms, the various and profound influences of fluid loading on the vibration of structures and their acoustic fields. The far field response aspects of a coupled fluid-structure system include subsonic surface wave at low frequencies; decay of leaky wave and associated beaming directivity; amplitude and decay rate of acoustic field on the plate; directivity at small angles for moderate frequencies; and directivity at all angles at low frequencies. The near field is also subject to strong fluid-loading effects, especially at low frequencies. For semi-infinite and finite geometries, the results are quite different except at high frequencies for velocities below the instability limit. The propagation of vibration energy along an irregular structure involves multiple back-scattering of structural waves by nonperiodic constraints leading to unattenuated propagation in the pass bands of a periodic structure, and confining energy exponentially around a site of excitation much as in the stop bands of a periodic structure. A final and major aspect noted concerns the excitation of fluid-loaded structures by turbulent boundary layer pressure fields, rather than by mechanical or acoustic excitation. (C.E.)