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Experimental and Computational Study of Tones Occurring with a Coaxial Nozzle The source of audible tones occurring with a coaxial nozzle in a range of low Mach numbers is explored experimentally as well as computationally. The hardware is comprised of an inner and an outer nozzle, without a center-body, that are held together by a set of four struts. With increasing jet Mach number (M(sub j)), first a tone occurred at about 2550 Hz around M(sub j)=0.06. At higher values of M(sub j) a tone at 5200 Hz dominated the noise spectra. The corresponding nondimensional frequency, based on effective thickness of the inner nozzle lip and jet exit velocity, turned out to be about 0.2, a value characteristic of Karmann vortex shedding. Thus, vortex shedding from the inner nozzle lip could be linked to the tones. From a comparison of the acoustic wavelengths and the nozzle dimensions, it was inferred that the vortex shedding excited a one-quarter-wave resonance within the divergent section of either the inner nozzle or the outer nozzle. This led to the generation of the sharp tones.
Document ID
Document Type
Conference Paper
Zaman, K. B. M. Q.
(NASA Glenn Research Center Cleveland, OH, United States)
Milanovic, I.
(Hartford Univ. West Hartford, CT, United States)
Fagan, A. F.
(NASA Glenn Research Center Cleveland, OH, United States)
Miller, C. J.
(NASA Glenn Research Center Cleveland, OH, United States)
Date Acquired
August 28, 2018
Publication Date
June 25, 2018
Subject Category
Aeronautics (General)
Report/Patent Number
Meeting Information
AIAA Aviation Forum(Atlanta, GA)
Funding Number(s)
WBS: WBS 110076.
Distribution Limits
Public Use Permitted.
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