THE SOUND RADIATION EFFICIENCY OF FINITE LENGTH ACOUSTICALLY THICK CIRCULAR CYLINDRICAL SHELLS UNDER MECHANICAL EXCITATION I: THEORETICAL ANALYSIS

✍ Scribed by C. WANG; J.C.S LAI

• Publisher: Elsevier Science
• Year: 2000
• Tongue: English
• Weight: 238 KB
• Volume: 232
• Category: Article
• ISSN: 0022-460X
• DOI: 10.1006/jsvi.1999.2749

✦ Synopsis

The acoustic radiation from circular cylindrical shells is of fundamental and applied interest primarily because cylindrical shells are widely used in industry, and because their acoustic behaviour is di!erent from that of beams and plates due to curvature e!ects. In previous studies of the subject, cylindrical shells have been categorized into acoustically thin and acoustically thick shells in terms of the ratio between the ring frequency f P and the critical frequency f ! , i.e., f P /f ! (1 for acoustically thin shells, and f P /f ! '1 for acoustically thick shells. For acoustically thin shells, it has been found by statistical methods that the radiation e$ciency has a peak at the ring frequency. Above the ring frequency, the shells behave like #at plates. For acoustically thick shells, especially with "nite length, however, the behavior is not so clear. From the analysis in the wavenumber domain, a formula for calculating the modal radiation e$ciency of "nite length circular cylindrical shells (immersed in light #uid) under mechanical excitation is obtained analytically. Based on this method, the modal-averaged sound radiation e$ciencies of acoustically thick circular cylindrical shells are calculated. It is found that unlike acoustically thin shells, the radiation e$ciencies of acoustically thick cylindrical shells very much depend on the acoustic behaviour of each individual vibration mode, and thus on the geometries and the boundary conditions. Results obtained by acoustic boundary element calculations and experiments verify these conclusions.