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The Effects of Acoustic Treatment on Pressure Disturbances From a Supersonic Jet in a Circular DuctThe pressure disturbances generated by an instability wave in the shear layer of a supersonic jet are studied for an axisymmetric jet inside a lined circular duct. For the supersonic jet, locally linear stability analysis with duct wall boundary conditions is used to calculate the eigenvalues and the eigenfunctions at each axial location. These values are used to determine the growth rates and phase velocities of the instability waves and the near field 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, and wall impedance, and the effects of these changes on non-axisymmetric modes. The primary results indicate that the effects of the duct wall on stability characteristics diminish as the outer flow increases and as the jet azimuthal mode number increases. Also, wall reflections are reduced when using a finite impedance boundary condition at the wall; but in addition, reflections are reduced and growth rates diminished by keeping the imaginary part of the impedance negative when using the negative exponential for the harmonic dependence.
Document ID
19970009619
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
November 1, 1996
Subject Category
Fluid Mechanics And Heat Transfer
Report/Patent Number
NASA-TM-107358
E-10513
NAS 1.15:107358
Report Number: NASA-TM-107358
Report Number: E-10513
Report Number: NAS 1.15:107358
Meeting Information
Meeting: International Mechanical Engineering Congress and Exposition
Location: Atlanta, GA
Country: United States
Start Date: November 17, 1996
End Date: November 22, 1996
Sponsors: American Society of Mechanical Engineers
Accession Number
97N15020
Funding Number(s)
PROJECT: RTOP 505-62-52
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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