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Spinning mode sound propagation in ducts with acoustic treatment and sheared flowThe propagation of spinning mode sound was considered for a cylindrical duct with sheared steady flow. Calculations concentrated on the determination of the wall optimum acoustic impedance and the maximum possible attenuation. Both the least attenuated and higher radial modes for spinning lobe patterns were considered. A parametric study was conducted over a wide range of Mach numbers, spinning lobe numbers, sound frequency, and boundary layer thickness. A correlation equation was developed from theoretical considerations starting with the thin boundary layer approximation of Eversman. This correlation agrees well with the more exact calculations for inlets and provides a single boundary layer refraction parameter which determines the change in optimum wall impedance due to refraction effects.
Document ID
19750009956
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Rice, E. J.
(NASA Lewis Research Center Cleveland, OH, United States)
Date Acquired
September 3, 2013
Publication Date
January 1, 1975
Subject Category
Acoustics
Report/Patent Number
NASA-TM-X-71672
E-8261
Meeting Information
Meeting: 2d Aeroacoustics Specialists Conf.
Location: Hampton, VA
Country: United States
Start Date: March 24, 1975
End Date: March 26, 1975
Sponsors: AIAA
Accession Number
75N18028
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
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