Modelling of High-Frequency Scattering from Elastic Spheres

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Authors
  1. Fawcett, J.A.
Corporate Authors
Defence Research Establishment Atlantic, Dartmouth NS (CAN)
Abstract
Acoustic monopoles and the principle of superposition (applied to sound pressure) are fundamental tools that can be used to construct theoretical dipole and cardioid sound sources. Strictly speaking, the size of these monopoles, and their separations when forming simple multipoles like dipole doublets, ust be small compared to the wavelengths emitted. In the practical field of sonar tarnsducer design, however, transduction devices have finite dimensions, and consequently, do not meet the basic size and separation criteria for their transmission to be accurately described by those of multipole sources. Nevertheless, there are transducers that produce good approximations to the omnidirectional, bidirectional, and unidirectional radiation patterns of monopole, dipole, and cardioid sources, respectively. One such device is the low-frequency (900 Hz) directional Class IV flextensional transducer. A single elmeent alone can produce omnidirection, dipole, and left/right cardioid patterns. This unique capability provides the array designer with many options for generating directional beams, compared to arrays composed solely of omnidirectional sources, In this work, the directivity patterns of a single Class IV element and a four-element orthogonal array are presented. TRUNCATED
Keywords
Elastic scattering;Specular reflection;Time domain
Report Number
DREA-TM-98-233 — Technical Memorandum
Date of publication
01 Feb 1999
Number of Pages
29
DSTKIM No
99-00948
CANDIS No
510978
Format(s):
Hardcopy;Document Image stored on Optical Disk

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