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Effects of Acoustically Lined Cylindrical Ducts on Instability Waves in Confined Supersonic JetsThe pressure disturbances generated by an instability wave in the shear layer of a supersonic jet are studied for an axisymmetric jet inside a lined cylindrical duct. For the supersonic jet, locally linear stability analysis with duct wall boundary conditions is used to calculate the eigenvalues and the eigenfunctions. These values are used to determine the growth rates and phase velocities of the instability waves and the radial pressure disturbance patterns. The study is confined to the dominant Kelvin-Helmholtz instability mode and to the region just downstream of the nozzle exit where the shear layer is growing but is still small in size compared to the radius of the duct. Numerical results are used to study the effects of changes in the outer flow, growth in the shear layer thickness, wall distance, wall impedance, and frequency. Results indicate that the effects of the duct wall on shear layer growth rates diminish as the outer flow increases. Also, wall reflections cause variations in growth rates depending on wall height and Strouhal number. These variations are due to the phase relationship between the outgoing and the reflected incoming pressure disturbances at the shear layer. The growth rate variations can be reduced and the maximum growth rate minimized by keeping the imaginary part of the impedance negative.
Document ID
19970026050
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Dahl, Milo D. (NASA Lewis Research Center Cleveland, OH United States)
Date Acquired
September 6, 2013
Publication Date
May 1, 1997
Subject Category
Fluid Mechanics And Heat Transfer
Report/Patent Number
NAS 1.15:107441
E-10709
NASA-TM-107441
AIAA Paper 97-1600
Meeting Information
Meeting: Aeroacoustics
Location: Atlanta, GA
Country: United States
Start Date: May 12, 1997
End Date: May 14, 1997
Sponsors: American Inst. of Aeronautics and Astronautics, Confederation of European Aerospace Societies
Accession Number
97N25417
Funding Number(s)
PROJECT: RTOP 505-62-52
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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