Transonic buffet control by means of upper Gurney flaps

This study investigates the possibility of controlling transonic buffet by means of a Gurney Flap with an upward deflection at the trailing edge of the airfoil (UGF). Different geometries and dimensions of UGFs have been studied for their impact on the buffet behaviour. The effectiveness of the UGFs has been tested experimentally with Schlieren and PIV in the transonic-supersonic wind tunnel of TU Delft at Ma=0.7, a=3.5. It is found that the best performing UGF is a straight UGF with a height of 1.5% or 2% of the chord. These UGFs allow the reduction of the energy associated with buffet. This result has been corroborated by a flow description of the phases of buffet, a spectral analysis and a POD approach. In addition, the straight UGFs resulted to be effective in a less developed buffet condition too.