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Optics and AcousticsAcoustic Detection and Detectors

Numerical Methods for Underwater Structural Acoustics

Authors: Howard Elman; Dianne O'Leary; Joel Saltz; Gilbert Stewart; MARYLAND UNIV COLLEGE PARK OFFICE OF RESEARCH ADMINISTRATION AND ADVANCEMENT
Abstract:
This report represents the status of the project referenced above as of June 30, 1995, the conclusion of the term of this grant. The project centered on a problem in structural acoustics: to determine the reflection properties of an underwater object interacting with sonar signals. To generate representative problems, we have been using the SARA package produced by H. Allik and D. Moore of Boit Beranek and Newman, New London, CT. This code uses a finite/infinite (quadratic) element formulation in the frequency domain. The resulting linear system, which is complex symmetric, is currently solved with heavy dependence on secondary storage (i.e., disk) by Gaussian elimination using a frontal approach, with no pivoting for stability. This method has given adequate numerical results, even though it might be expected to fail due to resonances in the system. It is also likely to be too costly to handle large problems, especially for three dimensional models. Our goal has been to investigate two alternative approaches that we expect will alleviate these difficulties: the use of iterative methods and the use of parallel sparse solvers.

Limitations: APPROVED FOR PUBLIC RELEASE
Description: Final rept. 1 Mar 94-30 Jun 95
Pages: 5
Report Date: 19 APR 96
Contract Number: N00014-94-1-0580
Report Number: A303313
Keywords relating to this report:
*UNDERWATER ACOUSTICS
ACOUSTIC REFLECTION
ACOUSTIC RESONANCE
ALGORITHMS
ELASTIC PROPERTIES
FINITE ELEMENT ANALYSIS
ITERATIONS
MATHEMATICAL PROGRAMMING
NUMERICAL METHODS AND PROCEDURES
SONAR SIGNALS
UNDERWATER STRUCTURES
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