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Published May 27, 2016 | Published
Conference Paper Open

Super- and multi-directive acoustic radiation by linear global modes of a turbulent jet

Abstract

The mean flow stability of a Mach 0.9 turbulent jet is investigated by means of global linear theory with a focus on acoustic effects. A novel class of resonant acoustic modes that are trapped within the potential core, and whose eigenvalues appear as discrete branches in the global stability spectrum, is studied in detail. A dispersion relation is reconstructed from the global modes, and shown to accurately predict energy bands observed in the PSD of a high-fidelity LES. Similarly, the acoustic far-field radiation patterns of the trapped modes are compared to the LES. A favorable agreement between the global mode waveforms and coherent structures educed from the LES is found for both the trapped acoustic wave component inside the core and the far-field radiation.

Additional Information

© 2016 by Oliver T. Schmidt. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. Published Online: 27 May 2016. OTS gratefully acknowledges support by DFG grant no. 3114/1-1. AT and TC gratefully acknowledge support from the Office of Naval Research under contract N0014-11-1-0753. AVGC and PJ acknowledge support from the Science Without Borders program (project number A073/2013). The LES study was supported by NAVAIR SBIR project, under the supervision of Dr. John T. Spyropoulos. The main LES calculations were carried out on CRAY XE6 machines at DoD HPC facilities in ERDC DSRC.

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August 20, 2023
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October 20, 2023