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Modal cut-on ratio in ducts with realistic flow profiles and its application to acoustic mode detection

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journal contribution
posted on 01.05.2019, 13:58 by J. R. Mathews, J. Chen, P. Joseph
This paper considers the modal cut-on ratio and its use in acoustic mode detection in ducts for a radially varying flow with swirl. These concepts have previously only been considered for the idealised case of uniform axial mean flow and no swirl, and thus in this paper they are generalised and extended to account for radial variations in axial and swirl Mach numbers. The cut-on ratio is shown to no longer satisfy a simple relation with the axial wavenumber, showing that while the cut-on ratio in arbitrary flow is defined its usefulness significantly decreases. Mode distribution functions are also investigated for radially varying flows, both in terms of cut-on ratio and axial wavenumber. In view of the deficiencies of the cut-on ratio highlighted in the paper a recent method for mode detection in ducts that uses just two microphones is generalised to deduce the mode amplitudes in radially varying flows, based on modal axial wavenumber rather than cut-on ratio. This method is shown to perform better than the existing method in radially varying and/or swirling flow in simple test configurations with an idealised source distribution.

Funding

All three authors were funded by and supported by the ENOVAL (ENgine mOdule VALidators) project, part of the Europeans Union's technology programme (grant number 604999). The authors would also like to thank Dr Brian Tester (ISVR) for providing the realistic flow data in Fig. 4a.

History

Citation

Journal of Sound and Vibration, 2018, 434, pp. 404-421

Author affiliation

/Organisation/COLLEGE OF SCIENCE AND ENGINEERING/Department of Engineering

Version

AM (Accepted Manuscript)

Published in

Journal of Sound and Vibration

Publisher

Elsevier

issn

0022-460X

Acceptance date

03/07/2018

Copyright date

2018

Available date

18/08/2019

Publisher version

https://www.sciencedirect.com/science/article/pii/S0022460X18304413?via=ihub

Notes

The file associated with this record is under embargo until 12 months after publication, in accordance with the publisher's self-archiving policy. The full text may be available through the publisher links provided above.

Language

en

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