The role of coherent structures inside a subsonic jet nozzle on the radiated sound

Vempati, C and Hemchandra, S and Samanta, A (2023) The role of coherent structures inside a subsonic jet nozzle on the radiated sound. In: AIAA SciTech Forum and Exposition, 2023, 23 January 2023through 27 January 2023, Orlando.

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Abstract

The nature of the wavepackets in the nozzle boundary layer and their influence on the wavepackets downstream of the nozzle exit is studied in a M = 0.9, ReD = 106 jet issued from a cylindrical nozzle with a transitional boundary layer. Coherent wavepackets are educed from LES data by performing Spectral Proper Orthogonal Decomposition (SPOD) in a global sense with the nozzle and jet flowfields considered together. We find that dynamics in the near-nozzle exit region is modulated by three types of coherent structures: wavepackets in the nozzle boundary layer, KH-type wavepackets in the initial shear layer region and the trapped acoustic modes inside the potential core of the jet. Further, the wavepackets in the nozzle boundary layer are directly linked to the KH-type wavepackets in the initial shear layer of the jet. We find that the wavepackets in the nozzle boundary layer are characterised by a change of phase in the wall-normal direction consistent with observations in previous investigations in the literature. Further, these structures become stretched and perturbed as they approach the nozzle exit possibly due to disturbances from the nozzle exit and scattering from the nozzle lip. © 2023, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.

Item Type:	Conference Paper
Publication:	AIAA SciTech Forum and Exposition, 2023
Publisher:	American Institute of Aeronautics and Astronautics Inc, AIAA
Additional Information:	The copyright for this article belongs to American Institute of Aeronautics and Astronautics Inc, AIAA.
Keywords:	Aeroacoustics; Nozzles; Principal component analysis; Shear flow; Wave packets, Coherent structure; Down-stream; Jet nozzle; Nozzle exits; Orthogonal decomposition; Proper Orthogonal; Radiated sound; Shear layer; Subsonic jets; Transitional boundary layers, Boundary layers
Department/Centre:	Division of Mechanical Sciences > Aerospace Engineering(Formerly Aeronautical Engineering)
Date Deposited:	11 Oct 2024 13:19
Last Modified:	11 Oct 2024 13:19
URI:	http://eprints.iisc.ac.in/id/eprint/86443

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