The low frequency sound from multipole sources in axisymmetric shear flows, with applications to jet noise
- 29 July 1975
- journal article
- research article
- Published by Cambridge University Press (CUP) in Journal of Fluid Mechanics
- Vol. 70 (3) , 595-604
- https://doi.org/10.1017/s0022112075002212
Abstract
We have obtained a closed-form solution for the sound radiation from multipole sources imbedded in an infinite cylindrical jet with an arbitrary velocity profile. It is valid in the limit where the wavelength is large compared with the jet radius. Simple formulae for the acoustic pressure field due to convected point sources are also obtained. The results show (in a simple way) how the mean flow affects the radiation pattern from the sources. For convected lateral quadrupoles it causes the exponentnof the Doppler factor (1 -Mcosθ)−nmultiplying the far-field pressure signal to be increased from the value of 3 used by Lighthill to 5.Keywords
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