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Generation and Radiation of Acoustic Waves from a 2D Shear LayerA thin free shear layer containing an inflection point in the mean velocity profile is inherently unstable. Disturbances in the flow field can excite the unstable behavior of a shear layer, if the appropriate combination of frequencies and shear layer thicknesses exists, causing instability waves to grow. For other combinations of frequencies and thicknesses, these instability waves remain neutral in amplitude or decay in the downstream direction. A growing instability wave radiates noise when its phase velocity becomes supersonic relative to the ambient speed of sound. This occurs primarily when the mean jet flow velocity is supersonic. Thus, the small disturbances in the flow, which themselves may generate noise, have generated an additional noise source. It is the purpose of this problem to test the ability of CAA to compute this additional source of noise. The problem is idealized such that the exciting disturbance is a fixed known acoustic source pulsating at a single frequency. The source is placed inside of a 2D jet with parallel flow; hence, the shear layer thickness is constant. With the source amplitude small enough, the problem is governed by the following set of linear equations given in dimensional form.
Document ID
Document Type
Conference Paper
Dahl, Milo D.
(NASA Glenn Research Center Cleveland, OH United States)
Date Acquired
August 20, 2013
Publication Date
August 1, 2000
Publication Information
Publication: Third Computational Aeroacoustics (CAA) Workshop on Benchmark Problems
Subject Category
Fluid Mechanics And Thermodynamics
Distribution Limits
Work of the US Gov. Public Use Permitted.

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IDRelationTitle20010061385Analytic PrimaryThird Computational Aeroacoustics (CAA) Workshop on Benchmark Problems
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