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Aircraft turbofan noiseTurbofan noise generation and suppression in aircraft engines are reviewed. The chain of physical processes which connect unsteady flow interactions with fan blades to far field noise is addressed. Mechanism identification and description, duct propagation, radiation, and acoustic suppression are discussed. The experimental techniques of fan inflow static tests are discussed. Rotor blade surface pressure and wake velocity measurements aid in the determination of the types and strengths of the generation mechanisms. Approaches to predicting or measuring acoustic mode content, optimizing treatment impedance to maximize attenuation, translating impedance into porous wall structure, and interpreting far field directivity patterns are illustrated by comparisons of analytical and experimental results. The interdependence of source and acoustic treatment design to minimize far field noise is emphasized. Areas requiring further research are discussed, and the relevance of aircraft turbofan results to quieting other turbomachinery installation is addressed.
Document ID
19870043870
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Groeneweg, J. F.
(NASA Lewis Research Center Cleveland, OH, United States)
Rice, E. J.
(NASA Lewis Research Center Cleveland, OH, United States)
Date Acquired
August 13, 2013
Publication Date
January 1, 1987
Publication Information
Publication: ASME, Transactions, Journal of Turbomachinery
Volume: 109
ISSN: 0889-504X
Subject Category
Acoustics
Accession Number
87A31144
Distribution Limits
Public
Copyright
Other

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