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Instability waves in a subsonic round jet detected using a near-field phased microphone array

Suzuki, Takao and Colonius, Tim (2006) Instability waves in a subsonic round jet detected using a near-field phased microphone array. Journal of Fluid Mechanics, 565 . pp. 197-226. ISSN 0022-1120. doi:10.1017/S0022112006001613.

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We propose a diagnostic technique to detect instability waves in a subsonic round jet using a phased microphone array. The detection algorithm is analogous to the beam-forming technique, which is typically used with a far-field microphone array to localize noise sources. By replacing the reference solutions used in the conventional beam-forming with eigenfunctions from linear stability analysis, the amplitudes of instability waves in the axisymmetric and first two azimuthal modes are inferred. Experimental measurements with particle image velocimetry and a database from direct numerical simulation are incorporated to design a conical array that is placed just outside the mixing layer near the nozzle exit. The proposed diagnostic technique is tested in experiments by checking for consistency of the radial decay, streamwise evolution and phase correlation of hydrodynamic pressure. The results demonstrate that in a statistical sense, the pressure field is consistent with instability waves evolving in the turbulent mean flow from the nozzle exit to the end of the potential core, particularly near the most amplified frequency of each azimuthal mode. We apply this technique to study the effects of jet Mach number and temperature ratio on the azimuthal mode balance and evolution of instability waves. We also compare the results from the beam-forming algorithm with the proper orthogonal decomposition and discuss some implications for jet noise.

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Colonius, Tim0000-0003-0326-3909
Additional Information:© 2006 Cambridge University Press. Reprinted with permission. (Received 11 January 2005 and in revised form 21 March 2006) 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 Centre for conducting the experiments and fruitful discussions. We would also like to thank Professor J. Freund for the DNS database and Drs S. Narayanan, R. Reba and R. Schlinker for technical discussions regarding jet noise experiments, as well as Professor P. Huerre for useful discussion.
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Aeroacoustics Research Consortium (AARC) of the Ohio Aerospace InstituteUNSPECIFIED
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:6100
Deposited By: Archive Administrator
Deposited On:17 Nov 2006
Last Modified:08 Nov 2021 20:31

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