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Theoretical methods to predict near-field fuselage installation effects due to inlet fan tones

Theoretical methods to predict near-field fuselage installation effects due to inlet fan tones
Theoretical methods to predict near-field fuselage installation effects due to inlet fan tones
There are many analytical models to predict turbofan noise radiation in a free field.

However, these models explicitly ignore the effect of the aeroplane components on the engine noise. The effects of the aeroplane on the radiated noise must be included because it is the installed engine that affects people in the cabin and community. The original contribution of this thesis is to present a theoretical model for the near-field fuselage installation effects on tonal noise radiating from a turbofan engine inlet.

Historically, the fuselage installation effects have been modelled using theoretical methods for open-rotor type sources. Installation effects include the scattering effect from the fuselage, and the refraction effect of the boundary layer running down the fuselage. In this thesis the established techniques are extended to include a new sophisticated analytical source for spinning modes radiating from a circular duct. The source model includes the diffraction effect of the duct lip. The model applies Fourier methods and implements the Wiener-Hopf method for diffraction. Owing to the physics of the problem, simplifications in geometry and flow do not curtail the validity of the predictions.

The refraction effect was quantified by evaluating the difference between sound pressure levels with and without the boundary layer. Upstream of the source the refraction leads to a paucity of surface acoustic pressure, yet downstream the boundary-layer effect was minimal. Further investigations led to an alternative method of simulating refraction by altering wavenumbers in Fourier space. The installation method was optimised for a turbulent boundary-layer profile by replacing a power-law with a scaled step-change boundary-layer profile.
University of Southampton
Gaffney, James
7d1a9e19-a1cc-4066-8d98-e9e29c2a0177
Gaffney, James
7d1a9e19-a1cc-4066-8d98-e9e29c2a0177
Mcalpine, Alan
aaf9e771-153d-4100-9e84-de4b14466ed7

Gaffney, James (2016) Theoretical methods to predict near-field fuselage installation effects due to inlet fan tones. University of Southampton, Doctoral Thesis, 207pp.

Record type: Thesis (Doctoral)

Abstract

There are many analytical models to predict turbofan noise radiation in a free field.

However, these models explicitly ignore the effect of the aeroplane components on the engine noise. The effects of the aeroplane on the radiated noise must be included because it is the installed engine that affects people in the cabin and community. The original contribution of this thesis is to present a theoretical model for the near-field fuselage installation effects on tonal noise radiating from a turbofan engine inlet.

Historically, the fuselage installation effects have been modelled using theoretical methods for open-rotor type sources. Installation effects include the scattering effect from the fuselage, and the refraction effect of the boundary layer running down the fuselage. In this thesis the established techniques are extended to include a new sophisticated analytical source for spinning modes radiating from a circular duct. The source model includes the diffraction effect of the duct lip. The model applies Fourier methods and implements the Wiener-Hopf method for diffraction. Owing to the physics of the problem, simplifications in geometry and flow do not curtail the validity of the predictions.

The refraction effect was quantified by evaluating the difference between sound pressure levels with and without the boundary layer. Upstream of the source the refraction leads to a paucity of surface acoustic pressure, yet downstream the boundary-layer effect was minimal. Further investigations led to an alternative method of simulating refraction by altering wavenumbers in Fourier space. The installation method was optimised for a turbulent boundary-layer profile by replacing a power-law with a scaled step-change boundary-layer profile.

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Published date: November 2016

Identifiers

Local EPrints ID: 413589
URI: http://eprints.soton.ac.uk/id/eprint/413589
PURE UUID: 9a8936a6-c27d-4b70-8ed6-2074e56dd055
ORCID for Alan Mcalpine: ORCID iD orcid.org/0000-0003-4189-2167

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Date deposited: 29 Aug 2017 16:30
Last modified: 14 Mar 2019 01:49

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Contributors

Author: James Gaffney
Thesis advisor: Alan Mcalpine ORCID iD

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