Airfoil in a high amplitude oscillating stream

dc.contributor.authorStrangfeld, Christoph
dc.contributor.authorMüller-Vahl, Hanns
dc.contributor.authorNayeri, Christian Navid
dc.contributor.authorPaschereit, Christian Oliver
dc.contributor.authorGreenblatt, D.
dc.date.accessioned2017-10-27T12:54:55Z
dc.date.available2017-10-27T12:54:55Z
dc.date.issued2016
dc.descriptionDieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.de
dc.descriptionThis publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.en
dc.description.abstractA combined theoretical and experimental investigation was carried out with the objective of evaluating theoretical predictions relating to a two-dimensional airfoil subjected to high amplitude harmonic oscillation of the free stream at constant angle of attack. Current theoretical approaches were reviewed and extended for the purposes of quantifying the bound, unsteady vortex sheet strength along the airfoil chord. This resulted in a closed form solution that is valid for arbitrary reduced frequencies and amplitudes. In the experiments, the bound, unsteady vortex strength of a symmetric 18 % thick airfoil at low angles of attack was measured in a dedicated unsteady wind tunnel at maximum reduced frequencies of 0.1 and at velocity oscillations less than or equal to 50 %. With the boundary layer tripped near the leading edge and mid-chord, the phase and amplitude variations of the lift coefficient corresponded reasonably well with the theory. Near the maximum lift coefficient overshoot, the data exhibited an additional high-frequency oscillation. Comparisons of the measured and predicted vortex sheet indicated the existence of a recirculation bubble upstream of the trailing edge which sheds into the wake and modifies the Kutta condition. Without boundary layer tripping, a mid-chord bubble is present that strengthens during flow deceleration and its shedding produces a dramatically different effect. Instead of a lift coefficient overshoot, as per the theory, the data exhibit a significant undershoot. This undershoot is also accompanied by high-frequency oscillations that are characterized by the bubble shedding. In summary, the location of bubble and its subsequent shedding play decisive roles in the resulting temporal aerodynamic loads.en
dc.identifier.eissn1469-7645
dc.identifier.issn0022-1120
dc.identifier.urihttps://depositonce.tu-berlin.de//handle/11303/7069
dc.identifier.urihttp://dx.doi.org/10.14279/depositonce-6378
dc.language.isoen
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/
dc.subject.ddc530 Physik
dc.subject.otheraerodynamicsen
dc.subject.othergeneral fluid mechanicsen
dc.subject.othervortex sheddingen
dc.titleAirfoil in a high amplitude oscillating streamen
dc.typeArticle
dc.type.versionpublishedVersion
dcterms.bibliographicCitation.doi10.1017/jfm.2016.126
dcterms.bibliographicCitation.journaltitleJournal of fluid mechanics
dcterms.bibliographicCitation.originalpublishernameCambridge University Press
dcterms.bibliographicCitation.originalpublisherplaceCambridge
dcterms.bibliographicCitation.pageend108
dcterms.bibliographicCitation.pagestart79
dcterms.bibliographicCitation.volume793
tub.accessrights.dnbdomain
tub.affiliationFak. 5 Verkehrs- und Maschinensysteme>Inst. Strömungsmechanik und Technische Akustik (ISTA)>FG Experimentelle Strömungsmechanikde
tub.affiliation.facultyFak. 5 Verkehrs- und Maschinensystemede
tub.affiliation.groupFG Experimentelle Strömungsmechanikde
tub.affiliation.instituteInst. Strömungsmechanik und Technische Akustik (ISTA)de
tub.publisher.universityorinstitutionTechnische Universität Berlin
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