Part-span approximation of tone noise propagation in an aeroengine intake. Part 2: non-linear propagation

Abstract

Part I of this study, reported separately, introduced a part-span approximation for linear propagation of fan tone noise in aeroengine intake ducts. Analytical and computational methods were used to understand how artificially changing the hub-to-tip ratio of a duct impacts the representation of acoustic modes and their propagation. In many representative cases, the approximation was successfully applied and potential sources of error were highlighted. This understanding is extended in the present paper to include non-linear effects. While conventional CFD methods can predict the acoustic field with reasonable accuracy, the computational expense is too high for iterative application during the design process. The research community also requires more efficient methods to understand modern challenges such as the impact of increased flow distortion with future UHBR (Ultra-High Bypass Ratio) designs. The effect of the part-span approximation is first assessed for high-amplitude acoustic waves in uniform ducts with uniform flow. The part-span approximation is then implemented for an axisymmetric, but otherwise realistic, intake geometry with non-uniform inflow and a realistic buzz-saw noise source. The results of this simulation are compared with results from a conventional full-span calculation. The approximation provides a significant saving in computational expense and successfully captures much of the acoustic content of interest.

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Identifiers

ORCID for Joseph S.P. Binns: orcid.org/0000-0001-6151-4038

ORCID for Long Wu: orcid.org/0009-0006-8578-7755

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