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Linear and nonlinear growth of secondary instabilities of crossflow vortices studied by PSE

Hein, Stefan (2014) Linear and nonlinear growth of secondary instabilities of crossflow vortices studied by PSE. Seminar on Math. Dept., Imperial College London, 2014-12-12, London, United Kingdom.

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Offizielle URL: http://www3.imperial.ac.uk/newsandeventspggrp/imperialcollege/naturalsciences/mathematics/ammpfluiddynamics/eventssummary/event_10-11-2014-15-11-27

Kurzfassung

Laminar-turbulent transition in (quasi-) three-dimensional boundary layers dominated by crossflow vortices is studied for the setup of the DLR swept-flat plate experiment. The linear and subsequent nonlinear stages of both the crossflow vortices and their high-frequency secondary instabilities are modelled by nonlinear parabolized stability equations (PSE). In the first part of the talk it is shown that those high-frequency secondary instabilities may develop from the interaction of stationary and low-frequency travelling crossflow vortices, a transition scenario usually more relevant in wind-tunnel experiments. In low-turbulence-level environments like free flight with stationary crossflow vortices being dominant in amplitude the high-frequency secondary instabilities presumably are triggered directly from environmental disturbances via a receptivity mechanism, however. Therefore, in the second part results from a different approach developed recently based on a bi-directional coupling between a secondary instability code and a PSE code are presented. Thereby, the nonlinear development of secondary instabilities including the generation of higher harmonics could be studied up to the stages where the feedback of the finite-amplitude secondary instability modes on the stationary crossflow vortices is no longer negligible and the skin-friction coefficient starts to deviate from that due to the mean flow distortion caused by the stationary crossflow modes alone. The latter could be used as a criterion for imminent laminar-turbulent transition within the saturation region of the stationary crossflow modes which was lacking in a nonlinear PSE analysis of crossflow-dominated transition until now.

elib-URL des Eintrags:https://elib.dlr.de/93725/
Dokumentart:Konferenzbeitrag (Vortrag)
Titel:Linear and nonlinear growth of secondary instabilities of crossflow vortices studied by PSE
Autoren:
AutorenInstitution oder E-Mail-AdresseAutoren-ORCID-iDORCID Put Code
Hein, Stefanstefan.hein (at) dlr.deNICHT SPEZIFIZIERTNICHT SPEZIFIZIERT
Datum:2014
Referierte Publikation:Nein
Open Access:Nein
Gold Open Access:Nein
In SCOPUS:Nein
In ISI Web of Science:Nein
Status:veröffentlicht
Stichwörter:laminar-turbulent transition, nonlinear PSE, crossflow vortices, secondary instability
Veranstaltungstitel:Seminar on Math. Dept., Imperial College London
Veranstaltungsort:London, United Kingdom
Veranstaltungsart:Andere
Veranstaltungsdatum:12 Dezember 2014
HGF - Forschungsbereich:Luftfahrt, Raumfahrt und Verkehr
HGF - Programm:Luftfahrt
HGF - Programmthema:Flugzeuge
DLR - Schwerpunkt:Luftfahrt
DLR - Forschungsgebiet:L AR - Aircraft Research
DLR - Teilgebiet (Projekt, Vorhaben):L - Militärische Technologien (alt)
Standort: Göttingen
Institute & Einrichtungen:Institut für Aerodynamik und Strömungstechnik > Hochgeschwindigkeitskonfigurationen
Hinterlegt von: Micknaus, Ilka
Hinterlegt am:17 Dez 2014 14:58
Letzte Änderung:24 Apr 2024 19:59

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