Active flow control for leading-edge vortex configurations

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The flow around delta wing configurations is characterized by the formation of large-scale leading edge vortices, linked to attached and separated, laminar and turbulentshear layers. These flow structures are associated with unsteadiness over a broad range of scales and comprise non-linear interaction. From an aerodynamic point of view, influencing the characteristic vortex flow instabilities, namely those related to the rolling up shear layer and to vortex burtsing, is of great interest due to the possibility of increasing the performance of such configurations as well as the stability at the borders of the flight envelope. Here, periodic oscillations of sectional, leading-edge active flap elements and pulsed blowing using slanted slots near the leading edge are used to manipulate and control the vortex flow. Actuation frequencies are correlated to the frequencies of the flow instability mechanisms. The investigations are conducted for a generic delta wing geometry used in a previous research program (BR 1511/1) featuring a large experimental and numerical data base. This data base comprises the case of partly developed, fully developed and burst leading-edge vortices depending geometrically fixed or free primary separation and angle of attack. Flow control is aimed to increase the aerodynamic efficiency and longitudinal and lateral stability in the high angle-of-attack regime (stall and post-stall regime) and to reduce structural dynamic loads by alleviating unsteady aerodynamic loads.