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Title: Mitigation of under-expanded supersonic jet noise through stepped nozzles
Authors: Wei, Xiaofeng
Mariani, Raffaello
Chua, Leok Poh
Lim, H. D.
Lu, Zhen Bo
Cui, Yongdong
New, Tze How
Keywords: Engineering::Mechanical engineering
Issue Date: 2019
Source: Wei, X., Mariani, R., Chua, L. P., Lim, H. D., Lu, Z. B., Cui, Y. & New, T. H. (2019). Mitigation of under-expanded supersonic jet noise through stepped nozzles. Journal of Sound and Vibration, 459, 114875-.
Project: MOE2014-T2-1-002
Journal: Journal of Sound and Vibration
Abstract: An experimental investigation into noise reduction of supersonic jets through nozzle trailing-edge modifications was conducted, whereby far-field acoustic measurements were captured for two different stepped nozzles under two distinct under-expanded conditions. When compared to a baseline nozzle, results show that stepped nozzles lead to significant noise reductions at certain polar and azimuthal angles. In particular, a maximum noise reduction of 6 dB is observed for the longest stepped nozzle at a nozzle-pressure-ratio of 4 and 0° azimuthal angle. Spectral analysis shows that the noise reduction is mainly due to reduction in broadband shock associated noise and elimination of jet screech phenomenon. Abrupt changes in nozzle lip lengths of the stepped nozzles appear to disrupt acoustic feedback loop, thus resulting in screech cessation. Qualitative schlieren imaging and quantitative schlieren measurements were subsequently performed to correlate the shock structures and density gradient fields with the resulting noise components. Unlike those produced by the baseline nozzle, shock structures generated by the stepped nozzles are highly irregular and the jet plumes undergo discernible deflections. Lastly, the reduction in broadband shock associated noise is related to the lower shock strengths, as demonstrated by the density gradient profiles.
ISSN: 0022-460X
DOI: 10.1016/j.jsv.2019.114875
Rights: © 2019 Elsevier Ltd. All rights reserved. This paper was published in Journal of Sound and Vibration and is made available with permission of Elsevier Ltd.
Fulltext Permission: open
Fulltext Availability: With Fulltext
Appears in Collections:MAE Journal Articles

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