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Boundary layers over wing sections
KTH, School of Engineering Sciences (SCI), Mechanics, Stability, Transition and Control. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, Centres, SeRC - Swedish e-Science Research Centre.
2017 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

The understanding of developing boundary layers over wings is an important topic from the perspective of industrial applications. An increased understanding would be consequential not only for achieving higher fuel efficiency but also in the design of aircraft control strategies. With these aims in mind, the current work aims to further the understanding of developing boundary layer over wingsections. The study is performed with two particular perspectives in mind -unsteady aerodynamic effects in a pitching airfoil and turbulent boundary layerstructure in non-equilibrium boundary layers over a stationary airfoil.The boundary layer evolution in unsteady natural laminar flow airfoils undergoing small-amplitude pitch-oscillations is investigated. For high Reynolds numbers the origins of the non-linear unsteady aerodynamic response of laminar airfoils is explained on the basis of quasi-steady assumptions. Temporal nonlinearitiesin aerodynamic forces are shown to be inherently linked to thenon-linearities of static aerodynamic force coefficients and that a simple phaselagconcept can model the observed non-linear unsteady response. On the other hand at lower Reynolds numbers, when there exists an unstable leading edgelaminar separation bubble, the unsteady response is dynamically rich and changes in boundary layer characteristics can be abrupt. Such quasi-steadyphase-lag concepts are no longer appropriate to explain the unsteady flow physics in such a case. For the case of stationary airfoils, flow statistics for flow around an airfoil at two different Reynolds numbers are compared to assess Reynolds number effects in non-equilibrium flows. Pressure gradient effects found to be stronger at low Reynolds numbers, leading to higher energy in the larger structures present  in the outer part of the turbulent boundary layer.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2017. , p. 25
Series
TRITA-MEK, ISSN 0348-467X ; 2017:15
National Category
Fluid Mechanics and Acoustics Aerospace Engineering
Research subject
Engineering Mechanics
Identifiers
URN: urn:nbn:se:kth:diva-217984ISBN: 978-91-7729-591-4 (print)OAI: oai:DiVA.org:kth-217984DiVA, id: diva2:1158507
Presentation
2017-12-13, D3, Lindstedtsvägen 5, KTH, Stockholm, 15:15 (English)
Opponent
Supervisors
Note

QC 20171121

Available from: 2017-11-21 Created: 2017-11-20 Last updated: 2017-11-22Bibliographically approved
List of papers
1. High-fidelity simulations of the flow around wings at high Reynolds numbers
Open this publication in new window or tab >>High-fidelity simulations of the flow around wings at high Reynolds numbers
Show others...
2017 (English)Manuscript (preprint) (Other academic)
National Category
Fluid Mechanics and Acoustics
Research subject
Engineering Mechanics
Identifiers
urn:nbn:se:kth:diva-217981 (URN)KTH/MEK/TR-17/15-SE (ISRN)978-91-7729-591-4 (ISBN)
Conference
10th International Symposium on Turbulence & Shear Flow Phenomenon
Note

QC 20171121

Available from: 2017-11-20 Created: 2017-11-20 Last updated: 2017-11-21Bibliographically approved
2. A re-examination of filter-based stabilization for spectral-element methods
Open this publication in new window or tab >>A re-examination of filter-based stabilization for spectral-element methods
2017 (English)Report (Other academic)
Publisher
p. 19
Series
TRITA-MEK, ISSN 0348-467X
National Category
Mechanical Engineering
Research subject
Engineering Mechanics
Identifiers
urn:nbn:se:kth:diva-217972 (URN)KTH/MEK/TR-17/15-SE (ISRN)978-91-7729-591-4 (ISBN)
Note

QC 20171121

Available from: 2017-11-20 Created: 2017-11-20 Last updated: 2017-11-21Bibliographically approved
3. Unsteady aerodynamic effects in small-amplitude pitch oscillations of an airfoil
Open this publication in new window or tab >>Unsteady aerodynamic effects in small-amplitude pitch oscillations of an airfoil
Show others...
(English)Manuscript (preprint) (Other academic)
National Category
Fluid Mechanics and Acoustics
Research subject
Engineering Mechanics
Identifiers
urn:nbn:se:kth:diva-217976 (URN)KTH/MEK/TR-17/15-SE (ISRN)
Note

QC 20171121

Available from: 2017-11-20 Created: 2017-11-20 Last updated: 2017-11-21Bibliographically approved
4. Dynamic response of laminar flow airfoils
Open this publication in new window or tab >>Dynamic response of laminar flow airfoils
2017 (English)Report (Other academic)
Series
TRITA-MEK, ISSN 0348-467X
National Category
Aerospace Engineering
Research subject
Engineering Mechanics
Identifiers
urn:nbn:se:kth:diva-217975 (URN)KTH/MEK/TR-17/15-SE (ISRN)978-91-7729-591-4 (ISBN)
Note

QC 20171121

Available from: 2017-11-20 Created: 2017-11-20 Last updated: 2017-11-21Bibliographically approved

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