Technical Briefs

Sound Radiation from a Supersonic Jet Passing Through a Partially Open Exhaust Duct

[+] Author and Article Information
M. Kandula1

 ASRC Aerospace NASA Kennedy Space Center, FL 32899, USAmax.kandula-1@nasa.gov


Corresponding author.

J. Vib. Acoust 133(6), 064503 (Nov 28, 2011) (5 pages) doi:10.1115/1.4004671 History: Received September 28, 2010; Revised March 30, 2011; Published November 28, 2011; Online November 28, 2011

The radiation of sound from a perfectly expanded Mach 2.5 cold supersonic jet of 25.4 mm exit diameter flowing through a partially open rigid-walled duct with an upstream J-deflector has been experimentally studied. In the experiments, the nozzle is mounted vertically, with the nozzle exit plane at a height of 73 jet diameters above ground level. Relative to the nozzle exit plane (NEP), the location of the duct inlet is varied at 10, 5, and –1 jet diameters. Far-field sound pressure levels were obtained at 54 jet diameters above ground with the aid of acoustic sensors equally spaced around a circular arc of radius equal to 80 jet diameters from the jet axis. Data on the jet acoustic field for the partially open duct were obtained and compared with those with a free jet and with a closed duct. The results suggest that for the partially open duct the overall sound pressure level (OASPL) decreases as the distance between the NEP and the duct inlet plane decreases, while the opposite trend is observed for the closed duct. It is also concluded that the observed peak frequency in the partially open duct increases above the free jet value as the angle from the duct axis is increased, and as the duct inlet plane becomes closer to the NEP.

Copyright © 2011 by American Society of Mechanical Engineers
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Figure 1

(a) Geometry of the ducted exhaust jet configuration, (b) a photographic view of the nozzle and duct setup, (c) acoustic measurement setup, (d) microphone array height for h/dj=10, (e) microphone array height for h/dj=5, (f) microphone array height for h/dj=-1

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Figure 2

(a) Comparison of OASPL for the free jet and the partially open duct, and (b) comparison of OASPL for the free jet and the closed duct [13]

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Figure 3

Spectral sound power for the free jet and the partially open duct



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