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A CAA Based Approach to Tone Haystacking

Ewert, R. and Kornow, O. and Delfs, J.W. and Yin, J. and Röber, T. and Rose, M. (2009) A CAA Based Approach to Tone Haystacking. In: AIAA Paper 2009-3217. 15th AIAA/CEAS Aeroacoustics Conference, 11 - 13 May 2009, Miami, Florida.

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The far-field noise spectra of jet engines show for certain jet configurations and turbine tones a characteristic spectral broadening effect, causing a reduction of tone peaks in favor of a more distributed spectral hump around each tone frequency. This haystacking effect likely occurs due to the interaction of the turbine tones with the unsteady turbulent jet shear layer. A better understanding of this effect may help to utilize it for noise reduction purposes. Furthermore, the effect is of interest for the measurement of tone sources in an open acoustic wind tunnel test section, since the tone will be scattered in the open jet shear layer. A correction for this measured broadening effect is desirable. A non-empirical computational approach to predict tone haystacking as a function of Reynolds number/jet shear layer characteristics is currently missing. This paper reports about ongoing work to utilize Computational Aeroacoustics (CAA) methods for the prediction of haystacking. In a first step CAA techniques are applied to simulate the propagation of tones through the time averaged steady exhaust of a jet engine. To simulate the haystacking effect with CAA, the unsteady turbulent base-flow is modeled with a 4D synthetic turbulence method. The employed RPM approach generates turbulence with all local statistical features as predicted by time-averaged RANS. To study the spectral broadening effect computationally, the experimental set-up of Candel is considered first, which involves an omnidirectional sound source located on the axis of a round jet. The analytical predictions show very good agreement with the general trends as measured by Candel for an observer position normal to the jet axis. The computations reveal a spectral shape, which is in good agreement with those found in the experiments. In a next step the methodology is combined with the exhaust problem to simulate sound propagation through the unsteady turbulent exhaust.

Item URL in elib:https://elib.dlr.de/60951/
Document Type:Conference or Workshop Item (Paper)
Title:A CAA Based Approach to Tone Haystacking
AuthorsInstitution or Email of AuthorsAuthor's ORCID iD
Ewert, R.Institute of Aerodynamics and Flow Technology, Technical Acoustics, roland.ewert (at) dlr.deUNSPECIFIED
Kornow, O.Institute of Aerodynamics and Flow Technology, Technical AcousticsUNSPECIFIED
Delfs, J.W.Institute of Aerodyanmics and Flow Technology, Technical AcousticsUNSPECIFIED
Yin, J.Institute of Aerodynamics and Flow Technology, Technical AcousticsUNSPECIFIED
Röber, T.Institute of Propulsion Technology, Numerical MethodsUNSPECIFIED
Rose, M.Rolls-Royce Deutschland, Eschenweg 11, Dahlewitz, 15827, Blankenfelde-Mahlow, GermanyUNSPECIFIED
Journal or Publication Title:AIAA Paper 2009-3217
Refereed publication:No
Open Access:No
Gold Open Access:No
In ISI Web of Science:No
Keywords:CAA, Haystacking, RANS, Candel Experiment, ISVR, FRPM
Event Title:15th AIAA/CEAS Aeroacoustics Conference
Event Location:Miami, Florida
Event Type:international Conference
Event Dates:11 - 13 May 2009
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Aeronautics
HGF - Program Themes:L VU - Air Traffic and Environment (old)
DLR - Research area:Aeronautics
DLR - Program:L VU - Air Traffic and Environment
DLR - Research theme (Project):L - Quiet Air Traffic (old)
Location: Braunschweig
Institutes and Institutions:Institute of Aerodynamics and Flow Technology > Technical Acoustics
Deposited By: Ewert, Dr.-Ing. Roland
Deposited On:26 Nov 2009 11:21
Last Modified:12 Dec 2013 20:45

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