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Experimental study of turbulent-jet wave packets and their acoustic efficiency

Breakey, David E. S. and Jordan, Peter and Cavalieri, André V. G. and Nogueira, Petrônio A. and Léon, Olivier and Colonius, Tim and Rodríguez, Daniel (2017) Experimental study of turbulent-jet wave packets and their acoustic efficiency. Physical Review Fluids, 2 (12). Art. No. 124601. ISSN 2469-990X. https://resolver.caltech.edu/CaltechAUTHORS:20171201-152324924

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Abstract

This paper details the statistical and time-resolved analysis of the relationship between the near-field pressure fluctuations of unforced, subsonic free jets (0.4 ≤ M ≤ 0.6) and their far-field sound emissions. Near-field and far-field microphone measurements were taken on a conical array close to the jets and an azimuthal ring at 20∘ to the jet axis, respectively. Recent velocity and pressure measurements indicate the presence of linear wave packets in the near field by closely matching predictions from the linear homogenous parabolized stability equations, but the agreement breaks down both beyond the end of the potential core and when considering higher order statistical moments, such as the two-point coherence. Proper orthogonal decomposition (POD), interpreted in terms of inhomogeneous linear models using the resolvent framework allows us to understand these discrepancies. A new technique is developed for projecting time-domain pressure measurements onto a statistically obtained POD basis, yielding the time-resolved activity of each POD mode and its correlation with the far field. A single POD mode, interpreted as an optimal high-gain structure that arises due to turbulent forcing, captures the salient near-field–far-field correlation signature; further, the signatures of the next two modes, understood as suboptimally forced structures, suggest that these POD modes represent higher order, acoustically important near-field behavior. An existing Green's-function-based technique is used to make far-field predictions, and results are interpreted in terms of POD/resolvent modes, indicating the acoustic importance of this higher order behavior. The technique is extended to provide time-domain far-field predictions.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1103/PhysRevFluids.2.124601DOIArticle
https://journals.aps.org/prfluids/abstract/10.1103/PhysRevFluids.2.124601PublisherArticle
ORCID:
AuthorORCID
Colonius, Tim0000-0003-0326-3909
Additional Information:© 2017 American Physical Society. Received 15 June 2017; published 1 December 2017. D.E.S.B. thanks Dr. Craig Meskell for his discussions concerning the analysis of the data. Science Foundation Ireland supported this work under Contract No. 09/RFP/ENM2469. D.E.S.B. was also supported by the Natural Sciences and Engineering Research Council of Canada. This work was partially supported through the EU-Russian program ORINOCO (FP7-AAT-2010-RTD-Russia; Project No. 266103) and by the Agence Nationale de la Recherche (ANR) Project No. ANR-12-BS09-0024 through the project Cool Jazz (COntrol-Oriented Linear and nonlinear models for Jet Aeroacoustic ZZ).
Funders:
Funding AgencyGrant Number
Science Foundation, Ireland09/RFP/ENM2469
Natural Sciences and Engineering Research Council of Canada (NSERC)UNSPECIFIED
European Research Council (ERC)266103
Agence Nationale de la Recherche (ANR)ANR-12-BS09-0024
Issue or Number:12
Record Number:CaltechAUTHORS:20171201-152324924
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20171201-152324924
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:83637
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:02 Dec 2017 04:43
Last Modified:03 Oct 2019 19:08

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