The University of Southampton
University of Southampton Institutional Repository

Evaluation of acoustic sources in an excited unstable laminar shear layer

Evaluation of acoustic sources in an excited unstable laminar shear layer
Evaluation of acoustic sources in an excited unstable laminar shear layer
The radiation of sound from artificial sources in a developing shear layer is studied numerically, in order to address an issue that arises in acoustic analogy models of jet noise: namely whether the unstable response of the mean-flow shear layer has a significant effect on sound radiation. Direct numerical simulation of a forced two-dimensional compressible laminar mixing layer has been carried out at a Reynolds number of 250, based on the mixing layer initial vorticity thickness and the upper free-stream velocity. The free-stream Mach numbers of the mixing layer are 0.9 and 0.45. The flow is excited with a single-frequency body force field that is acoustically compact and is derived from an applied-stress distribution. Sound radiation from the mixing layer is calculated at the forcing frequency, and compared with radiation from a uniform flow under the same forcing. Comparisons are shown for the most-unstable forcing frequency over a wide amplitude range. The pressure radiated on either side of the mixing layer differs very little from that radiated into a uniform flow of the same Mach number under the same forcing, although the higher forcing amplitudes used are sufficient to trigger the non-linear process of vortex roll-up in the case of the mixing layer. The dominant source position for the radiated pressure at the forcing frequency is estimated via a wavenumber–frequency domain analysis. It is found to be close to the location of the applied forcing, with little contribution from mixing-layer vortical structures that develop downstream.
1475-472X
91-108
Hu, Z.W.
dd985844-1e6b-44ba-9e1d-fa57c6c88d65
Morfey, C.L.
d5f9a8d0-7d8a-4915-a522-bf49dee111f2
Sandham, N.D.
0024d8cd-c788-4811-a470-57934fbdcf97
Hu, Z.W.
dd985844-1e6b-44ba-9e1d-fa57c6c88d65
Morfey, C.L.
d5f9a8d0-7d8a-4915-a522-bf49dee111f2
Sandham, N.D.
0024d8cd-c788-4811-a470-57934fbdcf97

Hu, Z.W., Morfey, C.L. and Sandham, N.D. (2006) Evaluation of acoustic sources in an excited unstable laminar shear layer. International Journal of Aeroacoustics, 5 (1), 91-108. (doi:10.1260/147547206775220416).

Record type: Article

Abstract

The radiation of sound from artificial sources in a developing shear layer is studied numerically, in order to address an issue that arises in acoustic analogy models of jet noise: namely whether the unstable response of the mean-flow shear layer has a significant effect on sound radiation. Direct numerical simulation of a forced two-dimensional compressible laminar mixing layer has been carried out at a Reynolds number of 250, based on the mixing layer initial vorticity thickness and the upper free-stream velocity. The free-stream Mach numbers of the mixing layer are 0.9 and 0.45. The flow is excited with a single-frequency body force field that is acoustically compact and is derived from an applied-stress distribution. Sound radiation from the mixing layer is calculated at the forcing frequency, and compared with radiation from a uniform flow under the same forcing. Comparisons are shown for the most-unstable forcing frequency over a wide amplitude range. The pressure radiated on either side of the mixing layer differs very little from that radiated into a uniform flow of the same Mach number under the same forcing, although the higher forcing amplitudes used are sufficient to trigger the non-linear process of vortex roll-up in the case of the mixing layer. The dominant source position for the radiated pressure at the forcing frequency is estimated via a wavenumber–frequency domain analysis. It is found to be close to the location of the applied forcing, with little contribution from mixing-layer vortical structures that develop downstream.

Full text not available from this repository.

More information

Published date: January 2006
Organisations: Aerodynamics & Flight Mechanics

Identifiers

Local EPrints ID: 28391
URI: https://eprints.soton.ac.uk/id/eprint/28391
ISSN: 1475-472X
PURE UUID: 1cc0c6c9-82de-4dac-ac9a-f13495afc449
ORCID for N.D. Sandham: ORCID iD orcid.org/0000-0002-5107-0944

Catalogue record

Date deposited: 28 Apr 2006
Last modified: 06 Jun 2018 12:55

Export record

Altmetrics

Contributors

Author: Z.W. Hu
Author: C.L. Morfey
Author: N.D. Sandham ORCID iD

University divisions

Download statistics

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton: eprints@soton.ac.uk

ePrints Soton supports OAI 2.0 with a base URL of https://eprints.soton.ac.uk/cgi/oai2

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.

×