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Comparison of non-modal-based and modalbased impedance eduction techniques

Weng, Chenyang and Enghardt, L. and Bake, Friedrich (2018) Comparison of non-modal-based and modalbased impedance eduction techniques. In: AIAA AVIATION 2018. 24th AIAA/CEAS Aeroacoustics Conference, 25.-29. June 2018, Atlanta, Georgia, USA. DOI: 10.2514/6.2018-3773

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A comparative study of four impedance eduction techniques is reported. Two of the techniques are based on numerically solving the 2-D convective Helmholtz equation as a non-modal-based boundary-value problem. The third technique is modal-based as it applies a mode expansion to reduce the dimension of the Helmholtz equation from 2-D to 1-D. The forth technique is also modal-based but the employed propagation model takes account of the boundary-layer viscothermal effects and allows for shear flow varying over a rectangular cross section. Measurements on a liner with and without mean-flow conditions are carried out using the DLR DUCT-R system. The measured data are used for the impedance eduction and the educed results are presented. The conclusions drawn from the limited number of test cases include: 1, all the eduction techniques, except for one, educe scattered impedance values when the resistance of the liner is low, 2, the non-modalbased and the modal-based techniques yield similar impedance values for the downstream-propagating waves (modes), but yield considerably different values for the upstream-propagating waves (modes), and 3, the model which includes a shear mean flow and the model which assumes uniform mean flow exhibit differences in their educed impedance; the differences are larger for the upstream-propagating modes than for the downstreampropagating modes.

Item URL in elib:https://elib.dlr.de/120827/
Document Type:Conference or Workshop Item (Speech)
Title:Comparison of non-modal-based and modalbased impedance eduction techniques
AuthorsInstitution or Email of AuthorsAuthors ORCID iD
Weng, Chenyangdlr, at-traUNSPECIFIED
Bake, FriedrichFriedrich.Bake (at) dlr.dehttps://orcid.org/0000-0002-3235-428X
Date:June 2018
Journal or Publication Title:AIAA AVIATION 2018
Refereed publication:Yes
Open Access:No
Gold Open Access:No
In ISI Web of Science:No
DOI :10.2514/6.2018-3773
Keywords:Impedance eduction, liner, modal and non-modal based methods
Event Title:24th AIAA/CEAS Aeroacoustics Conference
Event Location:Atlanta, Georgia, USA
Event Type:international Conference
Event Dates:25.-29. June 2018
Organizer:AIAA / CEAS
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Aeronautics
HGF - Program Themes:propulsion systems
DLR - Research area:Aeronautics
DLR - Program:L ER - Engine Research
DLR - Research theme (Project):L - Turbine Technologies
Location: Berlin-Charlottenburg
Institutes and Institutions:Institute of Propulsion Technology > Engine Acoustic
Deposited By: Bake, Dr.-Ing. Friedrich
Deposited On:09 Jul 2018 09:40
Last Modified:09 Jul 2018 09:40

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