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Acoustic disturbance from gas non-uniformities convected through a nozzle

Marble, F. E. and Candel, S. M. (1977) Acoustic disturbance from gas non-uniformities convected through a nozzle. Journal of Sound and Vibration, 55 (2). pp. 225-243. ISSN 0022-460X. doi:10.1016/0022-460X(77)90596-X.

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The non-steady flow generated by convection of gas containing non-uniform temperature regions or "entropy spots" through a nozzle is examined analytically as a source of acoustic disturbance. The first portion of the investigation treats the "compact nozzle", the case where all wave lengths are much longer than the nozzle. Strengths of transmitted and reflected one-dimensional waves are given for supersonic and subsonic nozzles and for one configuration of supersonic nozzle with normal shock at the outlet. In addition to a wave reflected from the nozzle inlet, the supersonic nozzle discharges two waves, one facing upstream and the other facing downstream. For reasonable values of the nozzle inlet Mach number, the pressure amplitude of each wave increases directly as the discharge Mach number. The acoustic perturbations from a supercritical nozzle of finite length, in which the undisturbed gas velocity increases linearly through the nozzle, are analyzed for several inlet and discharge Mach number values and over a wide frequency range. The results, which agree with the compact analysis for low frequency, deviate considerably as the frequency rises, achieving pressure fluctuation levels of several times the compact values. It is shown that this result originates in a phase shift between the two waves emitted downstream and that the pressure fluctuations for moderate frequencies may be approximated from the compact analysis with an appropriate phase shift. In all cases, the pressure fluctuations caused by a 2% fluctuation in absolute inlet temperature are large enough to require consideration in acoustic analysis of nozzles or turbine blade channels.

Item Type:Article
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Additional Information:© 1977 Published by Elsevier Science Ltd. Received 6 September 1976; revised 1 July 1977. Available online 24 July 2003.
Group:Guggenheim Jet Propulsion Center
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Guggenheim Jet Propulsion CenterUNSPECIFIED
Issue or Number:2
Record Number:CaltechAUTHORS:20101214-073952475
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Official Citation:Marble, F. E. and S. M. Candel (1977). "Acoustic disturbance from gas non-uniformities convected through a nozzle." Journal of Sound and Vibration 55(2): 225-243.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:21340
Deposited By: Ruth Sustaita
Deposited On:14 Dec 2010 17:16
Last Modified:09 Nov 2021 00:08

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