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An experimental study of transmission, reflection and scattering of sound in a free jet flight simulation facility and comparison with theoryWhen a free jet (or open jet) is used as a wind tunnel to simulate the effects of flight on model noise sources, it is necessary to calibrate out the effects of the free jet shear layer on the transmitted sound, since the shear layer is absent in the real flight case. In this paper, a theoretical calibration procedure for this purpose is first summarized; following this, the results of an experimental program, designed to test the validity of the various components of the calibration procedure, are described. The experiments are conducted by using a point sound source located at various axial positions within the free jet potential core. By using broadband excitation and cross-correlation methods, the angle changes associated with ray paths across the shear layer are first established. Measurements are then made simultaneously inside and outside the free jet along the proper ray paths to determine the amplitude changes across the shear layer. It is shown that both the angle and amplitude changes can be predicted accurately by theory. It is also found that internal reflection at the shear layer is significant only for large ray angles in the forward quadrant where total internal reflection occurs. Finally, the effects of sound absorption and scattering by the shear layer turbulence are also examined experimentally.
Document ID
19810044539
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Ahuja, K. K.
(Lockheed-Georgia Co. Marietta, GA, United States)
Tanna, H. K.
(Lockheed-Georgia Co. Marietta, GA, United States)
Tester, B. J.
(Lockheed-Georgia Co. Marietta, Ga., United States)
Date Acquired
August 11, 2013
Publication Date
March 8, 1981
Publication Information
Publication: Journal of Sound and Vibration
Volume: 75
Subject Category
Acoustics
Accession Number
81A28943
Funding Number(s)
CONTRACT_GRANT: NAS3-20050
Distribution Limits
Public
Copyright
Other

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