NDLI: Refraction of sound emitted near solid boundaries from a sheared jet

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Refraction of sound emitted near solid boundaries from a sheared jet

Content Provider	NASA Technical Reports Server (NTRS)
Author	Krejsa, Eugene A. Oyedrian, Ayo A. Dill, Loren H.
Copyright Year	1998
Description	A mathematical model is developed to describe the sound emitted from an arbitrary point within a turbulent flow near solid boundaries. A unidirectional, transversely sheared mean flow is assumed, and the cross-section of the cold jet is of arbitrary shape. The analysis begins with Lilley's formulation of aerodynamic noise and, depending upon the specific model of turbulence used, leads via Fourier analysis to an expression for the spectral density of the intensity of the far-field sound emitted from a unit volume of turbulence. The expressions require solution of a reduced Green's function of Lilley's equation as well as certain moving axis velocity correlations of the turbulence. Integration over the entire flow field is required in order to predict the sound emitted by the complete flow. Calculations are presented for sound emitted from a plugflow jet exiting a semi-infinite flat duct. Polar plots of the far-field directivity show the dependence upon frequency and source position within the duct. Certain model problems are suggested to investigate the effect of duct termination, duct geometry, and mean flow shear upon the far-field sound.
File Size	2401945
Page Count	48
File Format	PDF
Alternate Webpage(s)	http://archive.org/details/NASA_NTRS_Archive_19980148001
Archival Resource Key	ark:/13960/t3b043b4w
Language	English
Publisher Date	1998-05-01
Access Restriction	Open
Subject Keyword	Acoustics Directivity Cold Gas Correlation Turbulent Flow Shear Flow Far Fields Flow Distribution Aerodynamic Noise Fourier Analysis Sound Intensity Mathematical Models Duct Geometry Ntrs Nasa Technical Reports Server (ntrs) Nasa Technical Reports Server Aerodynamics Aircraft Aerospace Engineering Aerospace Aeronautic Space Science
Content Type	Text
Resource Type	Technical Report

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