The influence of nozzle-exit boundary-layer state on evolution and radiation of wavepackets in subsonic jets

Vempati, C and Hemchandra, S and Samanta, A (2022) The influence of nozzle-exit boundary-layer state on evolution and radiation of wavepackets in subsonic jets. In: 28th AIAA/CEAS Aeroacoustics Conference, 2022, 14 - 17 June 2022, Southampton.

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Abstract

The influence of the nozzle lip on the potentially-radiating turbulent structures in its vicinity is investigated in addition to investigating the radiating characteristics of the small-scale turbulent structures in the nozzle boundary layer. Studies are conducted by considering two sets of permeable Ffowcs Williams and Hawkings (FW-H) surfaces which instead of encapsulating the nozzle are inside it and their farfield spectra is compared against the “true” farfield spectra of the configuration. In the first set of FW-H surfaces, the nozzle lip is outside the FW-H surface while in second set, turbulent structures in the nozzle boundary layer are left outside it. We find that the nozzle lip has no role in the farfield spectra for tt <≈ 2 and thus for peak frequencies. At high frequencies, significant deviations from the true spectra of the configuration are found due to not including the nozzle lip in the FW-H surface. We also observe that turbulent structures inside the nozzle radiate to the far-field at mid to high frequencies (St >≈ 0.7). Comparisons against previous studies suggest that the ability of the turbulent structures inside the nozzle to radiate is a function of Mach number of the flow. Further, both the small-scale structures in the nozzle and near-nozzle lip sources do not contribute to low frequency noise.

Item Type:	Conference Paper
Publication:	28th AIAA/CEAS Aeroacoustics Conference, 2022
Publisher:	American Institute of Aeronautics and Astronautics Inc, AIAA
Additional Information:	The copyright for this article belongs to the American Institute of Aeronautics and Astronautics Inc, AIAA.
Keywords:	Atmospheric thermodynamics; Aviation; Boundary layer flow; Boundary layers, Far field spectra; High frequency HF; Nozzle exits; Peak frequencies; Radiating characteristic; Small scale; Subsonic jets; Turbulent structures; Williams, Nozzles
Department/Centre:	Division of Mechanical Sciences > Aerospace Engineering(Formerly Aeronautical Engineering)
Date Deposited:	23 Aug 2022 05:44
Last Modified:	23 Aug 2022 05:44
URI:	https://eprints.iisc.ac.in/id/eprint/76176

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