Large-eddy simulations (LESs) of low-Reynolds-number flow ( Re = 50,000 ) over a NACA0018 airfoil are performed to investigate flow control at the stall angle of attack (15 deg) by low-amplitude surface waves (actuations) of different types (backward/forward traveling and standing waves) on the airfoil’s suction side. It is found that the backward (toward downstream) traveling waves, inspired from aquatic swimmers, are more effective than forward traveling and standing wave actuations. The results of simulations show that a backward traveling wave with a reduced frequency f * = 4 ( f * = f L / U , where f is frequency; L , chord length; and U , free flow velocity), a nondimensional wavelength λ * = 0.2 ( λ * = λ / L , where λ is dimensional wavelength), and a nondimensional amplitude a * = 0.002 ( a * = a / L , where a is dimensional amplitude) can suppress stall. In contrast, the flow over the airfoil with either standing or forward traveling wave actuations separates from the leading edge similar to the baseline. Consequently, the backward traveling wave creates the highest lift-to-drag ratio. For traveling waves at a higher amplitude ( a * = 0.008 ), however, the shear layer becomes unstable from the actuation point and creates periodic coherent structures. Therefore, the lift coefficient decreases compared with the low-amplitude case.


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    Title :

    Controlling Flow Separation on a Thick Airfoil Using Backward Traveling Waves


    Contributors:

    Published in:

    AIAA Journal ; 58 , 9 ; 3799-3807


    Publication date :

    2020-09-01




    Type of media :

    Conference paper , Article (Journal)


    Type of material :

    Electronic Resource


    Language :

    English






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