Water tunnel experiments on chordwise-flexible airfoils heaving with constant amplitude have been carried out for Reynolds numbers of 9000 to 27000. A degree of flexibility was found to increase both thrust coefficient and propulsive efficiency. Measurements of the flow field revealed stronger trailing-edge vortices corresponding to higher thrust coefficients, and weaker leading-edge vortices corresponding to higher efficiencies. By analogy with a rigid airfoil in coupled heave and pitch, thrust coefficient and propulsive efficiency were found to be functions of the Strouhal number and pitch phase angle. Propulsive efficiency peaks at a pitch phase angle of 95-100 deg (consistent with experimental and computational simulations of rigid airfoils in coupled heave and pitch), and a Strouhal number of 0.29, which lies in the middle of the range observed in nature. Thrust peaks at pitch phase angles in the region of 110-120 deg, but at higher Strouhal numbers. The results suggest the effect of chordwise flexibility is beneficial for purely heaving airfoils at low Reynolds numbers.


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    Title :

    Flexible flapping airfoil propulsion at low Reynolds numbers


    Additional title:

    Schuberzeugung mit einem vertikal schwingenden biegsamen Tragflügel bei niedrigen Reynoldszahlen


    Contributors:
    Heathcote, S. (author) / Gursul, I. (author)

    Published in:

    AIAA Journal (online) ; 45 , 5 ; 1066-1079


    Publication date :

    2007


    Size :

    14 Seiten, 21 Bilder, 55 Quellen




    Type of media :

    Article (Journal)


    Type of material :

    Print


    Language :

    English




    Flexible Flapping Airfoil Propulsion at Low Reynolds Numbers

    Heathcote, Sam / Gursul, Ismet | AIAA | 2005


    Flexible Flapping Airfoil Propulsion at Low Reynolds Numbers

    Sam Heathcote / Ismet Gursul | AIAA | 2007


    Flexible Flapping Airfoil Propulsion at Low Reynolds Numbers

    Heathcote, S. / Gursul, I. / American Institute of Aeronautics and Astronautics | British Library Conference Proceedings | 2005



    Aerodynamic Analysis of Flapping Airfoil Propulsion at Low Reynolds Numbers

    Windte, Jan / Radespiel, Rolf / Neef, Matthias | Springer Verlag | 2005