The aerodynamic loads on a two-dimensional airfoil can be altered with an active Gurney flap placed at the trailing edge. The flap can be moved either to the suction side for lift reduction or to the pressure side for lift enhancement. Measurements on a FX 63 -137 airfoil with a finite as well as a full span active Gurney flap were conducted in the wind tunnel. The dynamic wake during the flaps movement was measured with a High Speed Mono PIV system at center-span location. Furthermore, the time-dependent stream-wise pressure distribution was measured with a wake rake at various spanwise positions. The time-dependent pressure measurements as well as the PIV snapshots were further analyzed with Fast Fourier Transformations as well as the Proper Orthogonal Decomposition technique. Results for the static non-moving Gurney flap have shown, that the position of the vortex street is altered depending on the position of the Gurney flap. The average flow-field showed the decamber mechanism which is responsible for altering the static loads. The frequency of the vortex street was found higher for the flap deflected to the suction side than to the pressure side. The wake development during the active flap deployment and retraction process was observed. Lift and drag development could be associated with a trigger to the wake development. It was found, that the change of lift was accompanied by a change of the vortex street in frequency as well as in vortex strength over the flap movement.
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