Effect of Flexible Flaps on Lift and Drag of Laminar Profile Flow

Artur Reiswich, Max Finster, Martin Heinrich and Rüdiger Schwarze
Additional contact information
Artur Reiswich: Institute of Mechanics and Fluid Dynamics, Lampadiusstraße 4, 09596 Freiberg, Germany
Max Finster: Institute of Mechanics and Fluid Dynamics, Lampadiusstraße 4, 09596 Freiberg, Germany
Martin Heinrich: Institute of Mechanics and Fluid Dynamics, Lampadiusstraße 4, 09596 Freiberg, Germany
Rüdiger Schwarze: Institute of Mechanics and Fluid Dynamics, Lampadiusstraße 4, 09596 Freiberg, Germany

Energies, 2020, vol. 13, issue 5, 1-16

Abstract: Experiments with elastic flaps applied on a common airfoil profile were performed to investigate positive effects on lift and drag coefficients. An NACA0020 profile was mounted on a force balance and placed in a wind tunnel. Elastic flaps were attached in rows at different positions on the upper profile surface. The Reynolds number of the flow based on the chord length of the profile is about 2 × 10 5 . The angle of attack is varied to identify the pre- and post-stall effects of the flaps. Polar diagrams are presented for different flap configurations to compare the effects of the flaps. The results showed that flaps generally increase the drag coefficient due to the additional skin friction and pressure drag. Furthermore, a significant increase of lift in the stall region was observed. The highest efficiency was obtained for the configuration with flaps at the leading and trailing edges of the profile. In this case, the critical angle was delayed and lift was increased in pre- and post-stall regions. This flap configuration was used in a gust simulation in the wind tunnel to model unsteady incoming flow at a critical angle of attack. This investigation showed that the flow separation at the critical angle was prevented. Additionally, smoke–wire experiments were performed for the stall region in order to visualize the flow around the airfoil. The averaged flow field results showed that the leading-edge flaps lean the flow more towards the airfoil surface and reduce the size of the separated region. This reduction improves the airfoil performance in the deep stall region.

Keywords: flexible flaps; separation control; stall delay (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2020
References: View complete reference list from CitEc
Citations: View citations in EconPapers (2)

Downloads: (external link)
https://www.mdpi.com/1996-1073/13/5/1077/pdf (application/pdf)
https://www.mdpi.com/1996-1073/13/5/1077/ (text/html)

Related works:
This item may be available elsewhere in EconPapers: Search for items with the same title.

Export reference: BibTeX RIS (EndNote, ProCite, RefMan) HTML/Text

Persistent link: https://EconPapers.repec.org/RePEc:gam:jeners:v:13:y:2020:i:5:p:1077-:d:326767

Access Statistics for this article

Energies is currently edited by Ms. Agatha Cao

More articles in Energies from MDPI
Bibliographic data for series maintained by MDPI Indexing Manager ().