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Accession Number
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N20120010286
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Title
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Uncertainty Analysis of the Grazing Flow Impedance Tube.
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Publication Date
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Jun 2012
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Media Count
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13p
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Personal Author
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M. C. Brown M. G. Jones W. R. Watson
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Abstract
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This paper outlines a methodology to identify the measurement uncertainty of NASA Langley s Grazing Flow Impedance Tube (GFIT) over its operating range, and to identify the parameters that most significantly contribute to the acoustic impedance prediction. Two acoustic liners are used for this study. The first is a single-layer, perforate-over-honeycomb liner that is nonlinear with respect to sound pressure level. The second consists of a wire-mesh facesheet and a honeycomb core, and is linear with respect to sound pressure level. These liners allow for evaluation of the effects of measurement uncertainty on impedances educed with linear and nonlinear liners. In general, the measurement uncertainty is observed to be larger for the nonlinear liners, with the largest uncertainty occurring near anti-resonance. A sensitivity analysis of the aerodynamic parameters (Mach number, static temperature, and static pressure) used in the impedance eduction process is also conducted using a Monte-Carlo approach. This sensitivity analysis demonstrates that the impedance eduction process is virtually insensitive to each of these parameters.
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Keywords
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Acoustic impedance
Grazing flow
Honeycomb structures
Linings
Mach number
Monte carlo method
Nonlinearity
Sensitivity analysis
Sound pressure
Static pressure
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Source Agency
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National Aeronautics and Space Administration
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NTIS Subject Category
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46A - Acoustics
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Corporate Author
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National Aeronautics and Space Administration, Hampton, VA. Langley Research Center.
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Document Type
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Conference proceedings
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Title Note
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N/A
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NTIS Issue Number
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1226
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Contract Number
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N/A
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