Acoustic scattering by a closed semi-infinite fluid-loaded elastic cylindrical shell

Author(s):  
E. A. Skelton
2020 ◽  
Vol 14 (2) ◽  
Author(s):  
Younes Khandouch ◽  
El Houcein Aassif ◽  
Said Agounad ◽  
Gérard Maze

The obtained results from previous studies done in the acoustic scattering of a plane wave by an elastic cylindrical shell, show that the acoustic resonances of a cylindrical shell are related to its physical and geometrical properties. In order to estimate the radius ratio of an airfield immersed cylindrical shell, using reduced cutoff frequencies of circumferential waves that propagate around it. In this work, an approach based on the artificial neural networks was proposed. This approach uses the reduced cutoff frequencies of circumferential waves, extracted using modal isolation plan representation us the analyzing data, in the object to obtain the value of the radius ratio corresponding to the studied cylindrical shell. The proposed approach allows us to estimate accurately the values of the radius ratio of a copper cylindrical shell, and can help us to resolve other problems related to scattering acoustic. Furthermore, it can be used to estimate various parameters of a cylindrical shell starting from the characteristics of which it is disposed. The proposed approach used in this study does not present any approximation as in the case of the natural mode method which assimilate the cylindrical shell to the plate with the same thickness.


1989 ◽  
Vol 25 (7) ◽  
pp. 662-667 ◽  
Author(s):  
O. B. Kachaenko ◽  
L. S. Pal'ko ◽  
N. A. Shul'ga

1989 ◽  
Vol 111 (3) ◽  
pp. 337-342 ◽  
Author(s):  
R. J. Silcox ◽  
H. C. Lester ◽  
S. B. Abler

This paper examines the physical mechanisms governing the use of active noise control in an extended volume of a cylindrical shell. Measured data were compared with computed results from a previously derived analytical model based on infinite shell theory. For both the analytical model and experiment, the radiation of external monopoles is coupled to the internal acoustic field through the radial displacement of the thin, elastic, cylindrical shell. An active noise control system was implemented inside the cylinder using a fixed array of discrete monopole sources, all of which lie in the plane of the exterior noise sources. Good agreement between measurement and prediction was obtained for both internal pressure response and overall noise reduction. Attenuations in the source plane greater than 15 dB were recorded along with a uniformly quieted noise environment over an indicative length inside the experimental model. Results indicate that for forced responses with extended axial distributions, axial arrays of control sources may be required. Finally, the Nyquist criteria for the number of azimuthal control sources is shown to provide for effective control over the full cylinder cross section.


2018 ◽  
Vol 141 (1) ◽  
Author(s):  
Christopher Gilles Doherty ◽  
Steve C. Southward ◽  
Andrew J. Hull

Reinforced cylindrical shells are used in numerous industries; common examples include undersea vehicles, aircraft, and industrial piping. Current models typically incorporate approximation theories to determine shell behavior, which are limited by both thickness and frequency. In addition, many applications feature coatings on the shell interior or exterior that normally have thicknesses which must also be considered. To increase the fidelity of such systems, this work develops an analytic model of an elastic cylindrical shell featuring periodically spaced ring stiffeners with a coating applied to the outer surface. There is an external fluid environment. Beginning with the equations of elasticity for a solid, spatial-domain displacement field solutions are developed incorporating unknown wave propagation coefficients. These fields are used to determine stresses at the boundaries of the shell and coating, which are then coupled with stresses from the stiffeners and fluid. The stress boundary conditions contain double-index infinite summations, which are decoupled, truncated, and recombined into a global matrix equation. The solution to this global equation results in the displacement responses of the system as well as the exterior scattered pressure field. An incident acoustic wave excitation is considered. Thin-shell reference models are used for validation, and the predicted system response to an example simulation is examined. It is shown that the reinforcing ribs and coating add significant complexity to the overall cylindrical shell model; however, the proposed approach enables the study of structural and acoustic responses of the coupled system.


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