NASA Logo

NTRS

NTRS - NASA Technical Reports Server

Back to Results
Acoustic wave propagation in heterogeneous structures including experimental validationA finite element model was developed to solve for the acoustic pressure and energy fields in a heterogeneous suppressor. The derivations from the governing equations assumed that the material properties could vary with position resulting in a heterogeneous variable property two-dimensional wave equation. This eliminated the necessity of finding the boundary conditions between different materials. For a two media region consisting of part air and part bulk absorber, a model was used to describe the bulk absorber properties in two directions. Complex metallic structures inside the air duct are simulated by simply changing element properties from air to the structural material in a pattern to describe the desired shapes. To verify the numerical theory, experiments were conducted without flow in a rectangular duct with a single folded cavity mounted above the duct and absorbing material mounted inside a cavity. Changes in a nearly plane wave sound field were measured on the wall opposite the absorbing cavity. Fairly good agreement was found in the standing wave pattern upstream of the absorber and in the decay of pressure level opposite the absorber, as a function of distance along the duct. The finite element model provides a convenient method for evaluating the acoustic properties of bulk absorbers.
Document ID
19890010594
Document Type
Technical Memorandum (TM)
Authors
Baumeister, Kenneth J. (NASA Lewis Research Center Cleveland, OH, United States)
Dahl, Milo D. (NASA Lewis Research Center Cleveland, OH, United States)
Date Acquired
September 5, 2013
Publication Date
April 1, 1989
Subject Category
PHYSICS (GENERAL)
Report/Patent Number
NASA-TM-101486
E-4622
NAS 1.15:101486
Meeting Information
Aeroacoustics Conference(San Antonio, TX)
Funding Number(s)
PROJECT: RTOP 505-62-21
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

Available Downloads

NameType 19890010594.pdf STI