Acoustic waves propagating in a submerged fluid-filled sherical shell

Acoustic intensity streamlines for a plane wave scattered on a fluid-filled spherical shell

The sound fields resulting from a plane wave incident on a spherical elastic shell are found. Both the internal and external fields due to the shell are considered and compared with well‐known results. The Rayleigh limit is discussed, and it is found that the external field is similar to that produced by a rigid sphere but with more complicated coefficients. The internal field is of a complicated nature but reasonable to consider for numerical computation. The sound fields for a hemispherical shell mounted on a rigid medium are obtained by the image method. Numerical results for the sound intensity at the center of the hemisphere are presented for various elastic materials.

Reflection and Transmission of Sound by Elastic Spherical Shells

The acoustic scattering by thin‐walled, evacuated, elastic spherical shells immersed in water is studied. The analytic structure of the scattering amplitude in the complex‐k plane is directly analyzed using Cauchy’s residue theorem, and dispersion curves are presented for the lowest elastic modes of the fluid‐loaded shell. It is found that fluid loading has a profound effect on the vacuum dynamical characteristics of the shell; the spherical equivalent of the first antisymmetric, flat‐plate Lamb wave for the fluid‐loaded shell bifurcates into two distinct modes near the frequency that the vacuum dispersion curve transitions from a subsonic to a supersonic phase velocity. By way of contrast, the spherical equivalent of the first symmetric Lamb wave is essentially unaffected. The salient features of the free‐field scattering process are also analyzed in terms of the resonance excitation of these modes.

The acoustic scattering by a submerged, spherical shell. I: The bifurcation of the dispersion curve for the spherical antisymmetric Lamb wave

Previously, a fundamentally oriented analysis was presented of the complex‐ka plane pole structure of the S matrix for a thin spherical shell for 0<ka<100 [Sammelmann et al, J Acoust Soc Am 85, 114–124 (1989)] In this analysis, it was concluded that fluid loading the first antisymmetric mode of the shell in vacuum had a rather violent effect; the mode bifurcated into two distinct modes near the coincidence frequency In this article, the relationship of the poles of the diffractive modes of impenetrable spheres and the eigenfrequencies of the shell in vacuum to the modes of the fluid‐loaded shell are precisely established by studying the complex‐ka plane trajectories of the S‐matrix poles under variations of the material parameters of the shell The evolution of these modes are also examined as the shell thickness is varied from 2% to 50% of the outer radius of the shell It is found that the limit of an elastic solid is not approached smoothly and that modal reorganizations similar to the bifurcati

Acoustic waves propagating in a submerged fluid-filled sherical shell

Citations

Acoustic intensity streamlines for a plane wave scattered on a fluid-filled spherical shell

References

Reflection and Transmission of Sound by Elastic Spherical Shells

The acoustic scattering by a submerged, spherical shell. I: The bifurcation of the dispersion curve for the spherical antisymmetric Lamb wave

The acoustic scattering by a submerged, spherical shell. III : Pole trajectories in the complex-ka plane

Acoustic intensity streamlines for a plane wave scattered on a fluid-filled spherical shell

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