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Acoustic Resonances in Aircraft High Lift Configurations

Koch, Werner und Hein, Stefan und Hohage, Thorsten und Schöberl, Joachim (2006) Acoustic Resonances in Aircraft High Lift Configurations. 12th Conference on the Mathematics of Finite Elements and Applications (MAFELAP 2006), 2006-06-13 - 2006-06-16, Brunel University, West London (UK).

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High lift devices have been pinpointed as important source of airframe noise during aircraft landing and approach. In addition to broadband noise strong tones were observed. The occurrence of low- and high-frequency tones under different operating conditions suggests the presence of different source mechanisms which are usually traced to unstable shear layers. These sources can be enhanced by weakly damped resonances. The objective of the present investigation is the computation of such resonances in a generic two-element high lift configuration. Neglecting mean flow effects an eigenvalue problem for the Laplace operator has to be solved numerically subject to homogeneous Neumann boundary conditions on the airfoils in conjunction with a radiation condition at infinity. Using the finite element method the latter is approximated by perfectly matched layer (PML) absorbing boundary conditions at the necessarily finite grid boundaries. The calculation of resonances reduces then to solving a large eigenvalue problem via Arnoldi algorithm. The physics behind the low- and high-frequency resonances is first demonstrated for the simple model of a circular cylinder with a rectangular cut-out. Without the cut out cavity the resonances of the circular cylinder are simply highly damped resonances of surface waves which can be computed analytically and thus provide a good check of our numerical method. On the other hand if the rectangular cavity is considered by itself damped cavity resonances are obtained for longitudinal and transversal cavity modes. For the cylinder with cut out cavity these two different resonances interact but are dominated by the longitudinal cavity resonances. It is shown that similar resonances are behind the low- and high-frequency resonances of a high-lift configuration albeit the more complicated geometry and the not completely closed slat cove cavity obliterates this. The surface wave resonances correspond to the low-frequency peaks observed in model tests whereas the resonances of the slat cove cavity enhance the high-frequency peaks found for different operating conditions.

Dokumentart:Konferenzbeitrag (Vortrag)
Titel:Acoustic Resonances in Aircraft High Lift Configurations
AutorenInstitution oder E-Mail-AdresseAutoren-ORCID-iD
Hohage, ThorstenGeorg-August-Universität GöttingenNICHT SPEZIFIZIERT
Schöberl, JoachimJohannes Kepler Universität LinzNICHT SPEZIFIZIERT
Referierte Publikation:Nein
In Open Access:Nein
In ISI Web of Science:Nein
Stichwörter:acoustic resonances, aircraft high lift configuration, perfectly matched layer (PML), surface waves, cavity resonances
Veranstaltungstitel:12th Conference on the Mathematics of Finite Elements and Applications (MAFELAP 2006)
Veranstaltungsort:Brunel University, West London (UK)
Veranstaltungsart:internationale Konferenz
Veranstaltungsdatum:2006-06-13 - 2006-06-16
Veranstalter :BICOM: The Brunel Institute of Computational Mathematics
HGF - Forschungsbereich:Verkehr und Weltraum (alt)
HGF - Programm:Luftfahrt
HGF - Programmthema:L VU - Luftverkehr und Umwelt (alt)
DLR - Schwerpunkt:Luftfahrt
DLR - Forschungsgebiet:L VU - Luftverkehr und Umwelt
DLR - Teilgebiet (Projekt, Vorhaben):L - Flugphysik (alt)
Standort: Göttingen
Institute & Einrichtungen:Institut für Aerodynamik und Strömungstechnik > Hubschrauber
Hinterlegt von: Hein, Dr.-Ing. Stefan
Hinterlegt am:06 Mär 2007
Letzte Änderung:14 Jan 2010 23:23

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