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A Caltech Library Repository Feedhttp://www.rssboard.org/rss-specificationpython-feedgenenTue, 16 Apr 2024 15:00:45 +0000Effect of flow on the acoustic reflection coefficient at a duct inlet
https://resolver.caltech.edu/CaltechAUTHORS:20101217-092218676
Authors: {'items': [{'id': 'Bohn-M-S', 'name': {'family': 'Bohn', 'given': 'M. S.'}}, {'id': 'Zukoski-E-E', 'name': {'family': 'Zukoski', 'given': 'E. E.'}}]}
Year: 1976
DOI: 10.1121/1.380993
The effect of duct Mach number upon the acoustic reflection coefficient at the inlet of a duct with mean
flow is investigated. An analysis, which models the duct inlet as a very short, one-dimensional nozzle over
which the mean flow is accelerated from rest, gives good agreement with some recent experimental results.
Discrepancies between the analysis and the experimental results are discussed in terms of radiation losses at
the inlet and real fluid-flow effects within the duct.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/kffek-6v129Response of a subsonic nozzle to acoustic and entropy disturbances
https://resolver.caltech.edu/CaltechAUTHORS:20101213-104516314
Authors: {'items': [{'id': 'Bohn-M-S', 'name': {'family': 'Bohn', 'given': 'M. S.'}}]}
Year: 1977
DOI: 10.1016/0022-460X(77)90647-2
The one-dimensional response of a subsonic nozzle flow to small pressure and entropy
disturbances is calculated. The response is expressed in terms of transmitted acoustic
waves (which propagate from the nozzle in the same direction as the disturbance wave)
and reflected acoustic waves (which propagate from the nozzle in the direction opposite to
that of the disturbance wave) for three independent disturbances: a downstreampropagating
acoustic wave impinging upon the nozzle inlet, an upstream-propagating
wave impinging upon the nozzle exit, and an entropy wave convecting through the nozzle.
The solution for high frequency disturbances is discussed and used with the compact (long
wavelength disturbance) solution to normalize several numerical calculations. The
normalization shows that the transmitted waves created by the two acoustic disturbances
may be represented by the same function offrequency for a given inlet and exit nozzle Mach
number. The same is seen to be true for the reflected waves created by the two acoustic
disturbances. The normalization allows results for a wide range of nozzle Mach number
distributions and disturbance frequencies to be presented concisely.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/rcbyj-4ny65Noise Produced by the Interaction of Acoustic Waves and Entropy Waves with High-Speed Nozzle Flows
https://resolver.caltech.edu/CaltechAUTHORS:20151111-164208663
Authors: {'items': [{'id': 'Bohn-M-S', 'name': {'family': 'Bohn', 'given': 'Mark S.'}}]}
Year: 2015
Some aspects of the noise generated internally by a turbojet
engine are considered analytically and experimentally. The emphasis is placed on the interaction of pressure fluctuations and entropy fluctuations,
produced by the combustion process in the engine, with
gradients in the mean flow through the turbine blades or the exhaust nozzle. The results are directly applicable to the problem of excess noise in aircraft powerplants and suggest that the phenomenon described is the dominant mechanism.
The one-dimensional interaction of pressure fluctuations and
entropy fluctuations with a subsonic nozzle is solved analytically. The acoustic waves produced by each of three independent disturbances are investigated. These disturbances, which interact with the nozzle
to augment the acoustic radiation, are (i) pressure waves incident from upstream, (ii) pressure waves incident from downstream, and (iii) entropy waves convected with the stream. It is found that results for a large number of physically interesting nozzles may be presented
in a concise manner.
Some of the second-order effects which result from the area
variations in a nozzle are investigated analytically. The interaction of an entropy wave with a small area variation is investigated and the two-dimensional duct modes, which propagate away from the nozzle, are calculated.
An experiment is described in which one-dimensional acoustic
waves and entropy waves are made to interact with a subsonic nozzle. The response of the nozzle to these disturbances is measured and compared with the response as calculated by the analytical model.
The interaction of two-dimensional entropy waves with a subsonic nozzle and with a supersonic nozzle is investigated experimentally.
The results are explained in terms of an analysis of the acoustic waves and entropy waves produced by a region of arbitrary heat addition in a duct with flow.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/rqegj-k2w04