Sound radiation from finite cylindrical shells, partially covered with longitudinal strips of compliant layer
✍ Scribed by B. Laulagnet; J.L. Guyader
- Publisher
- Elsevier Science
- Year
- 1995
- Tongue
- English
- Weight
- 673 KB
- Volume
- 186
- Category
- Article
- ISSN
- 0022-460X
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✦ Synopsis
A vibro-acoustic model of a finite cylindrical shell partially covered with a compliant material layer is presented. The finite shell is terminated by a cylindrical rigid baffle and is covered by strips of compliant material lying parallel to the shell axis. The support shell motion is obtained by using Flu¨gge's operator and the layer is taken to be a locally reacting material having dissipative properties but without thickness. The whole system is excited by mean of a harmonic driving force applied to the supporting shell. In the infinite exterior medium, the acoustic pressure satisfies the Helmholtz equation. The acoustic pressure and the shell displacement are expanded in the eigenfunctions of the finite, non-covered, in vacuo, cylindrical shell. This leads to the construction of linear systems whose unknowns are the modal amplitudes of the pressure and of the shell displacement. If the cross-section of the partially covered shell has a plane of symmetry, the linear system splits into two independent, symmetric and antisymmetric parts. Nevertheless, each system displays coupling of circumferential order, meaning that the problem is no longer axisymmetric, as the totally covered problem was. Numerical results concerning acoustic radiation in water (radiated power) and shell vibration (radial quadratic velocity of the shell) are presented. They exhibit a surprising influence of the partial covering of a shell by a compliant layer: namely, that partially covering a shell in water can considerably increase the radiation compared to that from the bare cylinder, in a frequency range located well below the coincidence frequency.