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Numerical Simulation of a Passive Control of the Flow Around an Aerofoil Using a Flexible, Self Adaptive Flaplet
KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, Centres, SeRC - Swedish e-Science Research Centre.
City Univ London, Sch Math Comp Sci & Engn, London EC1V 0HB, England..
City Univ London, Sch Math Comp Sci & Engn, London EC1V 0HB, England..
2018 (English)In: Flow Turbulence and Combustion, ISSN 1386-6184, E-ISSN 1573-1987, Vol. 100, no 4, p. 1111-1143Article in journal (Refereed) Published
Abstract [en]

Self-activated feathers are used by almost all birds to adapt their wing characteristics to delay stall or to moderate its adverse effects (e.g., during landing or sudden increase in angle of attack due to gusts). Some of the feathers are believed to pop up as a consequence of flow separation and to interact with the flow and produce beneficial modifications of the unsteady vorticity field. The use of self adaptive flaplets in aircrafts, inspired by birds feathers, requires the understanding of the physical mechanisms leading to the mentioned aerodynamic benefits and the determination of the characteristics of optimal flaps including their size, positioning and ideal fabrication material. In this framework, this numerical study is divided in two parts. Firstly, in a simplified scenario, we determine the main characteristics that render a flap mounted on an aerofoil at high angle of attack able to deliver increased lift and improved aerodynamic efficiency, by varying its length, position and its natural frequency. Later on, a detailed direct numerical simulation analysis is used to understand the origin of the aerodynamic benefits introduced by the flaplet movement induced by the interaction with the flow field. The parametric study that has been carried out, reveals that an optimal flap can deliver a mean lift increase of about 20% on a NACA0020 aerofoil at an incidence of 20 (o) degrees. The results obtained from the direct numerical simulation of the flow field around the aerofoil equipped with the optimal flap at a chord Reynolds number of 2 x 10(4) shows that the flaplet movement is mainly induced by a cyclic passage of a large recirculation bubble on the aerofoil suction side. In turns, when the flap is pushed downward, the induced plane jet displaces the trailing edge vortices further downstream, away from the wing, moderating the downforce generated by those vortices and regularising the shedding cycle that appears to be much more organised when the optimal flaplet configuration is selected.

Place, publisher, year, edition, pages
Springer, 2018. Vol. 100, no 4, p. 1111-1143
Keywords [en]
NACA0020 wing, Passive control, Adaptive flap
National Category
Applied Mechanics
Identifiers
URN: urn:nbn:se:kth:diva-230481DOI: 10.1007/s10494-018-9914-6ISI: 000433113900014Scopus ID: 2-s2.0-85046017413OAI: oai:DiVA.org:kth-230481DiVA, id: diva2:1217718
Conference
European Drag Reduction and Flow Control Meeting (EDRFCM), APR 03-06, 2017, Monte Porzio Catone, Italy
Funder
EU, FP7, Seventh Framework Programme, 334954Swedish e‐Science Research Center
Note

QC 20180613

Available from: 2018-06-13 Created: 2018-06-13 Last updated: 2018-06-13Bibliographically approved

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Rosti, Marco E.

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