Active Flow Control with an Oscillating Dropped-Hinge Flap

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High-lift systems extend the flight envelope to low airspeeds and enable short take-off and landing distances. In order to further improve the performance of classical high-lift systems, active flow control systems are being investigated. The method for active flow control investigated in this project can suppress the separation of the flow, as was shown in preliminary work within a joint project between RWTH and TUM using numerical methods. To achieve active flow control, a dropped-hinge flap of an high-lift configuration is set into harmonic oscillating movement around the hinge point. The influence of an oscillating dropped-hinge flap on the lift coefficient strongly depends on the oscillation frequency. Thus, in our own preliminary work, the effect of the active flow influence was only shown in a certain frequency range. Effects of the oscillating gap size on the gap flow and of the oscillating flap surface on the boundary layer near the wall were identified as influencing variables. In order to better understand these effects, numerical and experimental studies are carried out to vary the oscillating gap width by tracking the spoiler on the one hand and the oscillation frequency and amplitude on the other. Parameter studies will be used to determine the potential for active flow control with an oscillating dropped-hinge flap over a wide range of angles of attack and flap angles. In addition, the influence of the Reynolds number will be considered by means of numerical studies.