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Relation Between Instability Waves and Low-Frequency Jet Noise Investigated with Phased-Microphone Arrays

Suzuki, Takao and Colonius, Tim (2006) Relation Between Instability Waves and Low-Frequency Jet Noise Investigated with Phased-Microphone Arrays. In: 44th AIAA Aerospace Sciences Meeting and Exhibit, 9-12 January 2006, Reno, NV.

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We study the relation between sound radiation patterns and the azimuthal-mode balance of instability-wave amplitude in a subsonic jet using mid-field and near-field phased- microphone arrays. To identify instability waves, we apply a least square optimization method, i.e. a beam-forming algorithm, to pressure signals obtained from a conical microphone array surrounding the jet from the nozzle exit to the end of the potential core. For the reference solutions, we use eigenfunctions based on linear stability analysis using the turbulent mean-velocity profiles and infer the amplitude of the axisymmetric and first two azimuthal modes associated with the Kelvin—Helmholtz instabilities. Likewise, pressure signals obtained from the mid-field array are decomposed into the azimuthal modes, and the directivity of low-frequency noise, particularly that of coherent sound, is analyzed. The azimuthal mode balances of the instability waves and acoustic waves are then compared, and the effects of compressibility, jet temperature and nozzle type (i.e. straight and chevron nozzles) are investigated. The results show that the directivity of low-frequency jet noise changes from the quadrupole radiation patterns to highly directive ones as increasing Mach number, while all instability modes are suppressed owing to compressibility without substantially varying the azimuthal-mode balance. The correlation of the azimuthal-mode balance between instability waves and coherent sound is stronger at higher Mach numbers. We also find that the radiation patterns of low-frequency noise change from quadrupoles to dipoles as the temperature increases at a low Mach number.

Item Type:Conference or Workshop Item (Paper)
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URLURL TypeDescription Paper Paper
Colonius, Tim0000-0003-0326-3909
Additional Information:© 2006 by T. Suzuki and T. Colonius. Published by the American Institute of Aeronautics and Astronautics, lnc., with permission. Published Online: 21 Jun 2012. The authors acknowledge the support of an AeroAcoustics Research Consortium (AARC) grant from the Ohio Aerospace Institute (OAI). We would like to express our deepest appreciation to Drs. J. Bridges, S.-S. Lee, and their colleagues at NASA Glenn Research Center for conducting all the experiments and fruitful discussions.
Funding AgencyGrant Number
Ohio Aerospace InstituteUNSPECIFIED
Subject Keywords:Aerospace Systems, Operations and Life Cycle
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AIAA Paper2006-622
Record Number:CaltechAUTHORS:20190718-165127273
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:97271
Deposited By: Melissa Ray
Deposited On:25 Jul 2019 14:57
Last Modified:16 Nov 2021 17:30

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