Active Dynamic Flow Control Studies on Rotor Blades

Higher Harmonic Control (HHC) and Individual Blade Control (IBC) technologies have reduced noise and vibration levels of rotors considerably. Further improvements are expected with on-blade devices, i.e. the rotor blade is active only along a limited spanwise section of high aerodynamic efficiency. On both advancing and retreating sides of the rotor disc local supersonic areas terminated by shock waves play a dominant role with respect to separation (dynamic stall) and buffet (moving shock) problems.The present paper deals with new design methodologies to deform blade sections dynamically. The objective of airfoil deformation is to avoid strong shock waves which are responsible for shock induced separation (dynamic stall) on the retreating blade and which are the origin of high speed impulsive noise levels on the advancing blade. A combination of different software components available at DLR Institute of Fluid Mechanics, i.e. Geometry Generation Tools and 2D-Time Accurate Navier-Stokes Codes have already shown their strong potential for the development of dynamic flow control devices. This system will be used intensively in the present study and systematically applied to separation and shock control problems.