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prediction of turbulence-generated noise in unheated jetsThe model-based approach, used by the JeNo code to predict jet noise spectral directivity, is described. A linearized form of Lilley's equation governs the non-causal Green s function of interest, with the non-linear terms on the right hand side identified as the source. A Reynolds-averaged Navier-Stokes (RANS) solution yields the required mean flow for the solution of the propagation Green s function in a locally parallel flow. The RANS solution also produces time- and length-scales needed to model the non-compact source, the turbulent velocity correlation tensor, with exponential temporal and spatial functions. It is shown that while an exact non-causal Green s function accurately predicts the observed shift in the location of the spectrum peak with angle as well as the angularity of sound at low to moderate Mach numbers, the polar directivity of radiated sound is not entirely captured by this Green s function at high subsonic and supersonic acoustic Mach numbers. Results presented for unheated jets in the Mach number range of 0.51 to 1.8 suggest that near the peak radiation angle of high-speed jets, a different source/Green s function convolution integral may be required in order to capture the peak observed directivity of jet noise. A sample Mach 0.90 heated jet is also discussed that highlights the requirements for a comprehensive jet noise prediction model.
Document ID
20050207369
Document Type
Technical Memorandum (TM)
Authors
Khavaran, Abbas
(QSS Group, Inc. Cleveland, OH, United States)
Bridges, James
(NASA Glenn Research Center Cleveland, OH, United States)
Georgiadis, Nicholas
(NASA Glenn Research Center Cleveland, OH, United States)
Date Acquired
September 7, 2013
Publication Date
July 1, 2005
Subject Category
Physics (General)
Report/Patent Number
NASA/TM-2005-213827/PT1
E-15186/PT1
Funding Number(s)
WBS: WBS 22-781-30-70
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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