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Correction published on 12 January 2022, see Energies 2022, 15(2), 524.
Article

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

Institute of Mechanics and Fluid Dynamics, Lampadiusstraße 4, 09596 Freiberg, Germany
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Energies 2020, 13(5), 1077; https://doi.org/10.3390/en13051077
Received: 15 January 2020 / Revised: 10 February 2020 / Accepted: 24 February 2020 / Published: 1 March 2020 / Corrected: 12 January 2022
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. View Full-Text
Keywords: flexible flaps; separation control; stall delay flexible flaps; separation control; stall delay
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MDPI and ACS Style

Reiswich, A.; Finster, M.; Heinrich, M.; Schwarze, R. Effect of Flexible Flaps on Lift and Drag of Laminar Profile Flow. Energies 2020, 13, 1077. https://doi.org/10.3390/en13051077

AMA Style

Reiswich A, Finster M, Heinrich M, Schwarze R. Effect of Flexible Flaps on Lift and Drag of Laminar Profile Flow. Energies. 2020; 13(5):1077. https://doi.org/10.3390/en13051077

Chicago/Turabian Style

Reiswich, Artur, Max Finster, Martin Heinrich, and Rüdiger Schwarze. 2020. "Effect of Flexible Flaps on Lift and Drag of Laminar Profile Flow" Energies 13, no. 5: 1077. https://doi.org/10.3390/en13051077

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