Airfoil Aerodynamic Performance Modification using Hybrid Surface Actuators

Global modifications of the aerodynamic characteristics of a commercial transport swept airfoil at cruise (low) angles of attack (when the baseline flow is fully attached) are achieved without moving control surfaces using hybrid actuators that are surface mounted on the pressure side of the airfoil 0.21c downstream of its leading edge. Control is effected by the manipulation of trapped vorticity concentrations that are induced by leveraging the presence of a miniature, O(0.01c) obstruction integrated with a synthetic jet actuator. At Rec = 1.3·10 6 , the operation of the hybrid actuators with maximum Cµ = 0.5 10 -3 results in continuous variation of the pressure drag from 15% greater to 50% less than the pressure drag of the baseline airfoil with minimal lift penalty and consequently an increase of the lift to pressure drag ratio in excess of a factor of two. High-resolution particle image velocimetry measurements at Rec = 6.7·10 5 are used to characterize the evolution of the boundary layer on the surface of the airfoil and estimate the total drag coefficient. It is shown that the overall drag is reduced by 29% and yields an increase in L/D of 27%.

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