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Passive low-aspect ratio cylinders mounted near the leading edge of an airfoil have been found to significantly improve the performance under dynamic stall conditions. In order to clarify the principle of operation these cylindrical disturbance generators (DG), high speed PIV and simultaneous pressure measurements have been performed on the pitching rotary aircraft wing profile OA209. Time resolved information for the flow field at mid chord and the pressure distribution was taken. In addition to the best configuration found in previous experiments, various geometries and sizes of these devices have been investigated. The experiments showed the effectiveness of the disturbance generators in reducing the negative pitching moment peak and hysteresis effects. Moreover, the development of stall compared to the clean case has been investigated and it was found that the disturbance generators reduce the strength and the distance normal to the chord of the vortices.

Passive low-aspect ratio cylinders mounted near the leading edge of an airfoil have been found to significantly improve the performance under dynamic stall conditions. In order to clarify the principle of operation these cylindrical disturbance generators (DG), high speed PIV and simultaneous pressure measurements have been performed on the pitching rotary aircraft wing profile OA209. Time resolved information for the flow field at mid chord and the pressure distribution was taken. In addition to the best configuration found in previous experiments, various geometries and sizes of these devices have been investigated. The experiments showed the effectiveness of the disturbance generators in reducing the negative pitching moment peak and hysteresis effects. Moreover, the development of stall compared to the clean case has been investigated and it was found that the disturbance generators reduce the strength and the distance normal to the chord of the vortices.

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