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Flexible flaps for separation control on a wing with low aspect ratio

Flexible flaps for separation control on a wing with low aspect ratio. Dipl. Ing. G. Patone Dr. W. Müller Dr. R. Bannasch Prof. Dr. Ing. I. Rechenberg. bionics pilot project:. Aeroflexible surface flaps as "eddy-breaks" built after the covert feathers of birds. Project partners:

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Flexible flaps for separation control on a wing with low aspect ratio

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  1. Flexible flaps for separation control on a wing with low aspect ratio Dipl. Ing. G. PatoneDr. W. MüllerDr. R. BannaschProf. Dr. Ing. I. Rechenberg

  2. bionics pilot project: Aeroflexible surface flaps as "eddy-breaks" built after the covert feathers of birds • Project partners: • DLR Abt. Turbulenzforschung • Firma Stemme GmbH • Fachgebiet Bionik und Evolutionstechnik an der TU-Berlin

  3. main objective: eddy

  4. Brown Skua with “eddy-flaps” eddy lifted covert feathers eddy- flaps

  5. aerofoil with eddy- flaps eddy- flaps

  6. goal: not like this but like this cL cL cD a cL cL cD a

  7. research goal • improving the stall behavior of an aerofoil • flaps should not have any negative effects while not active • flaps should work without external controls

  8. experimental setup at the wind tunnel lift-balance wind tunnel 10m/s NACA 2412 aerofoil with an aspect ratio of 3.5 Re= 130.000 drag-balance pressure sensor and scanivalve

  9. porosity schematic pressure distribution px > py impervious materials are lifted off by the pressure differences porous materials remain on the surface

  10. aerofoil with silk flaps silk steel wire

  11. silk flaps

  12. polar diagram for ‘perforated plastic sheet’ flaps

  13. aerofoil for pressure distribution

  14. pressure distribution at 16 degrees without flaps with flaps incident airflow

  15. pressure distribution at 19 degrees without flaps with flaps incident airflow

  16. flow visualisation trapped vortex trapped eddy

  17. pressure distribution at 36 degrees without flaps with flaps incident airflow

  18. polar diagram (calculated from all measuring rows) a

  19. lift distribution without flaps at different angles of attack

  20. lift distribution with flaps at different angles of attack

  21. summary: • eddy flaps prevent sudden drop in lift generation during stall • pressure distribution indicates: eddy-flaps restrict eddy to hind part of aerofoil outlook: • automatic contour adapting flaps • dynamic stall behaviour

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