Accession Number:

ADA238302

Title:

Lamb and Creeping Waves Around Submerged Spherical Shells Resonantly Excited by Sound Scattering. 2: Further Applications

Descriptive Note:

Corporate Author:

NAVAL OCEANOGRAPHIC AND ATMOSPHERIC RESEARCH LAB STENNIS SPACE CENTER MS

Personal Author(s):

Report Date:

1991-04-01

Pagination or Media Count:

15.0

Abstract:

Scattering of plane sound waves from an air-filled steel spherical shell submerged. In frequency band OK sub 1 A500 is studied. Analysis is based on a methodology proposed that uses the three-dimensional equations of dynamic elasticity to describe shell motions and to predict its sonar scattering cross section. This is valid at all frequencies, for shells of any thickness, constant curvature, and it accounts for their fluid-loaded condition. It is used to predict the cross sections, which are later interpreted on the basis of the various resonance features that manifest themselves in the frequency response. The spectral locations of the resonances depend on various types of elastic waves propagating along the shell, or in surrounding fluid. Exact plots are generated for phase velocities of these lamb waves always accounting for curvature and fluid-loading effects present on the shell, without appeals to plate waves or theories. Some dispersion plots were generated using the Donnell Shell-Theory approximation, which seems to yield accurate results up to the coincidence frequency. Aside from the broad resonance lobe present at the coincidence frequency, there is another high-frequency resonance lobe, due to a thickness-resonance response curve for a thin shell, around its coincidence frequency, serves to identify origins of the various types of observed resonance features and relate them to elastic and acoustic waves that propagate along the shell or outer fluid. Many computer-generated graphs are displayed to illustrate these points.

Subject Categories:

  • Numerical Mathematics
  • Statistics and Probability
  • Acoustics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE