Wave Propagation on an Acoustically Perturbed Jet
Date
1979
Authors
Fletcher, Neville H.
Thwaites, S.
Journal Title
Journal ISSN
Volume Title
Publisher
European Acoustics Association
Abstract
Theories of the initiation and propagation of transverse sinuous disturbances on an air jet
emerging from a flue slit into a transverse acoustic velocity field are reviewed and brought into
a form suitable for comparison with experiment. Available experimental data is then reviewed
and is found to be only moderately well accounted for by the existing theory. A new series of
experimental determinations of wave velocity on a jet .under conditions relevant to sound generation
in musical instruments is then described, these measurements extending over a larger
range of frequencies and blowing pressures than earlier measurements. For jets with Reynolds
number below about 1000 the wave velocity is found to be constant along the length of the jet
and to depend not upon the jet velocity V but rather upon the integral J of v2 across the width
of the jet. At low frequencies, w, the wave velocity is approximately 0.7 (J w)l/3, in agreement
with existing theory, but at higher frequencies it becomes independent of co and approximately
given by 50 J (where S.I. units are implied). Wave amplification along the jet is also· studied
and the wave amplitude found to increase like exp (μx) where μ is positive only below a cPitical
frequency w*, dependent on the jet parameters. For the jets studied, μis of order 1x103 m-1
below w*. A simple theory based on dimensional analysis is proposed to describe these experimental
results.
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Acta Acustica united with Acustica
Type
Journal article
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Open Access
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