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Wavepacket intermittency and its role in turbulent jet noise

Schmidt, Oliver T. and Colonius, Tim and Brès, Guillaume A. (2017) Wavepacket intermittency and its role in turbulent jet noise. In: 55th AIAA Aerospace Sciences Meeting, 9-13 January 2017, Grapevine, TX.

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The intermittent behavior of large-scale coherent structures in turbulent jets is studied. These structures are the primary source of jet noise, and their emitted sound is in turn characterized by rapid amplitude modulations of the pressure field. These high-energy bursts are well portrayed in the frequency-time domain by means of time-local analysis techniques. Scaleograms obtained from wavelet transforms of a single-point pressure signals, for example, enable the identification of such loud events at specific locations. Our interest, however, is in the time-local behavior of the coherent structures as a whole to gain a physical understanding of jet noise generation. For that purpose, a time series of large-eddy simulation snapshots is projected onto two sets of modal basis functions that describe the large-scale structures in the frequency-domain. The first modal basis consists of frequency-domain, or spectral, POD modes that are empirically deduced from the data. The second basis is comprised of resolvent response modes that are obtained from a linear frequency-response analysis of the mean flow. The proposed method allows us to visualize the intermittent behavior of the modal solutions in the frequency-time domain in terms of magnitude contours of the projection coefficient. The results can then be interpreted in an analogous way to wavelet scaleograms. The limitations, benefits and the potential of the method to yield a low-order representation of the flow in the time domain are discussed.

Item Type:Conference or Workshop Item (Paper)
Related URLs:
URLURL TypeDescription Paper Paper
Schmidt, Oliver T.0000-0002-7097-0235
Colonius, Tim0000-0003-0326-3909
Brès, Guillaume A.0000-0003-2507-8659
Additional Information:© 2017 by Oliver T. Schmidt, Tim Colonius, Guillaume A. Bres. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. Published Online: 5 Jan 2017. This research was supported in part by a grant from the Office of Naval Research (grant No. N00014-16-1-2445) with Dr. Knox Millsaps as program manager. Oliver Schmidt was supported by DFG grant No. SCHM 3114/1-1. The LES study was performed at Cascade Technologies, with support from NAVAIR SBIR project, under the supervision of Dr. John T. Spyropoulos. The main LES calculations were carried out on DoD HPC systems in ERDC DSRC.
Funding AgencyGrant Number
Office of Naval Research (ONR)N00014-16-1-2445
Deutsche Forschungsgemeinschaft (DFG)SCHM 3114/1-1
Naval Air Systems Command (NAVAIR)UNSPECIFIED
Subject Keywords:Aeroacoustics
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Other Numbering System NameOther Numbering System ID
AIAA Paper2017-0686
Record Number:CaltechAUTHORS:20190709-092100791
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:96971
Deposited By: Melissa Ray
Deposited On:11 Jul 2019 16:47
Last Modified:16 Nov 2021 17:25

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