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Spatial Stability Analysis of Subsonic Jets Modified for Low-Frequency Noise Reduction

Uzun, Ali and Alvi, Farrukh S. and Colonius, Tim and Hussaini, M. Yousuff (2015) Spatial Stability Analysis of Subsonic Jets Modified for Low-Frequency Noise Reduction. AIAA Journal, 53 (8). pp. 2335-2358. ISSN 0001-1452.

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This study performs a spatial stability analysis of several jets that have previously been investigated in terms of their noise radiation. The cases include a round jet and two chevron nozzle jets with varying penetration angle. The instability wave evolution in the near-nozzle region is examined to seek for clues as to how and why the mean flow azimuthal inhomogeneity introduced by chevrons modifies the low-frequency noise component. A biglobal stability analysis is performed to determine the most unstable modes on an initial plane. The downstream evolution of the most unstable modes is then computed via three-dimensional parabolized stability equations. The azimuthal mean flow inhomogeneity introduced by chevrons is found to modify instability wave growth rates and phase speeds. Findings indicate that the near-field hydrodynamic pressure oscillations of round jet instability modes are suppressed by chevron jets. For the same modal excitation amplitude at the inlet, the two chevron jets generate considerably lower pressure fluctuations than the round jet. It is also shown that the chevron jet with the lowest hydrodynamic pressure fluctuation levels is the jet with the lowest far-field low-frequency noise output among the three jets.

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Colonius, Tim0000-0003-0326-3909
Additional Information:© 2015 by the authors. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. Received 25 June 2014; revision received 30 March 2015; accepted for publication 1 April 2015; published online 20 May 2015. This work was supported by the Florida Center for Advanced Aero-Propulsion. This work was also supported partially by grants from the U.S. Army Research Office and the U.S. Air Force Office of Scientific Research. Some of the work was carried out while the first and the last authors visited the third author at the California Institute of Technology on several occasions. We acknowledge useful discussions with Aniruddha Sinha and Kristjan Gudmundsson during the course of this work. We thank both Philip Morris and graduate student Brian Davis for providing the data from their stability analysis calculations for comparison with our results. This work was also supported in part by the National Science Foundation through Extreme Science and Engineering Discovery Environment (XSEDE) resources provided by the National Institute for Computational Sciences (NICS) under grant TG-MCA06N043. The computations used NICS Cray XT5 System Kraken and the Department of Defense High Performance Computing Modernization Program supercomputers.
Funding AgencyGrant Number
Florida Center for Advanced Aero-PropulsionUNSPECIFIED
Army Research Office (ARO)UNSPECIFIED
Air Force Office of Scientific Research (AFOSR)UNSPECIFIED
Issue or Number:8
Record Number:CaltechAUTHORS:20150814-110653004
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Official Citation:Ali Uzun, Farrukh S. Alvi, Tim Colonius, and M. Yousuff Hussaini. "Spatial Stability Analysis of Subsonic Jets Modified for Low-Frequency Noise Reduction", AIAA Journal, Vol. 53, No. 8 (2015), pp. 2335-2358. doi: 10.2514/1.J053719
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:59533
Deposited By: Tony Diaz
Deposited On:14 Aug 2015 18:28
Last Modified:03 Oct 2019 08:48

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