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Streaks and coherent structures in jets from round and serrated nozzles

Rigas, Georgios and Pickering, Ethan and Schmidt, Oliver and Nogueira, Petrônio A. S. and Cavalieri, André V. G. and Brès, Guillaume A. and Colonius, Tim (2019) Streaks and coherent structures in jets from round and serrated nozzles. In: 25th AIAA/CEAS Aeroacoustics Conference, 20-23 May 2019, Delft, Netherlands.

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Hydrodynamic instabilities are directly related to large-scale coherent structures that are correlated with jet noise emission. Unravelling and accurately predicting their fundamental dynamics shows a promising direction for designing quieter jet engines. In this study, we analyze high-fidelity large-eddy simulation data of a turbulent Mach 0.4 round jet and a Mach 1.5 chevron jet. Using spectral proper orthogonal decomposition we identify, beyond the well-known Kelvin–Helmoholtz and Orr mechanisms, elongated alternating streamwise streaks of high and low-speed fluid that have been associated with a non-modal lift-up effect in wall-bounded shear flows. In the global three-dimensional domain, the most energetic streaks manifest for azimuthal wavenumber m = 1 and frequency St → 0. Furthermore, for the chevron jet, streaks and streamwise vortices appear due to the presence of the serrated nozzle, and they inherit the periodicity of the nozzle geometry. Finally, local (planar) spectral proper orthogonal decomposition is used to analyze the coherent structures of the chevron jet flow. Near the nozzle exit, antisymmetric and symmetric modes appear to be amplified and linked to the presence of the chevrons/streaks. Further downstream, the most energetic modes share similar characteristics to the ones observed in round jets.

Item Type:Conference or Workshop Item (Paper)
Related URLs:
URLURL TypeDescription Paper Paper
Rigas, Georgios0000-0001-6692-6437
Pickering, Ethan0000-0002-4485-6359
Schmidt, Oliver0000-0002-7097-0235
Cavalieri, André V. G.0000-0003-4283-0232
Brès, Guillaume A.0000-0003-2507-8659
Colonius, Tim0000-0003-0326-3909
Additional Information:© 2019 by the American Institute of Aeronautics and Astronautics, Inc. Published Online: 18 May 2019. This research was supported in part by a grant from the Office of Naval Research (grant No. N00014-16-1-2445) with Dr. Steven Martens as program manager. The LES study was performed at Cascade Technologies, with additional support from NAVAIR, under the supervision of Dr. John T. Spyropoulos. The main LES calculations were carried out on DoD HPC systems in ERDC DSRC. G.R. and T.C. also acknowledge the support of the Boeing Company through a Strategic Research and Development Relationship Agreement CT-BA-GTA-1.
Funding AgencyGrant Number
Office of Naval Research (ONR)N00014-16-1-2445
Naval Air Systems Command (NAVAIR)UNSPECIFIED
Boeing Company Strategic Research and Development RelationshipCT-BA-GTA-1
Subject Keywords:Aeroacoustics
Other Numbering System:
Other Numbering System NameOther Numbering System ID
AIAA Paper2019-2597
Record Number:CaltechAUTHORS:20190709-092102068
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:96975
Deposited By: Melissa Ray
Deposited On:11 Jul 2019 23:04
Last Modified:16 Nov 2021 17:25

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