Accession Number : ADA119369

Title :   Glory and Rainbow Enhanced Acoustic Backscattering from Fluid Spheres: Models for Diffracted Axial Focusing.

Descriptive Note : Technical rept. 1 Jul 81-31 Aug 82,

Corporate Author : WASHINGTON STATE UNIV PULLMAN DEPT OF PHYSICS

Personal Author(s) : Marston,Philip L ; Langley,Dean S

PDF Url : ADA119369

Report Date : 01 Sep 1982

Pagination or Media Count : 57

Abstract : Transmitted-wave contributions to backscattering from large fluid spheres are calculated. Amplitudes due to glory rays are enhanced, relative to those of axial reflections, because of focusing. The glory pressure amplitudes are proportional to a2(ka)1/2 where a is the sphere's radius and k is the wavenumber. The model, though similar in form to one for optical scattering from air bubbles contains new features to facilitate the summing of amplitudes in a range of angles. An additional enhancement due to rainbow focusing is modeled for certain sound velocity ratios M; for these M the backscattered amplitude is proportional to a2(ka)2/3. Major features of the exact scattering are reproduced by these models when ka = 1000 and (with defects) ka = 100. The enhancements are not intrinsically due to resonance. Applications to the design of passive sonar targets are noted. (Author)

Descriptors :   *ACOUSTIC SCATTERING, *UNDERWATER ACOUSTICS, INVERSE SCATTERING, FOCUSING, BACKSCATTERING, SPHERES, ELASTIC WAVES, PASSIVE SONAR

Subject Categories : Acoustic Detection and Detectors
      Acoustics

Distribution Statement : APPROVED FOR PUBLIC RELEASE