Dynamic Flow Control on Rotor Blades: Comprehensive Numerical and Experimental Tools at DLR-Göttingen

Dynamic flow control on rotor blades is a major subject in helicopter flow research and has recently been verified by HHC- (Higher Harmonic Control) and IBC- (Individual Blade Control) concepts. With these control devices only the complete rotor blade can be influenced leading to some severe limitations. Further improvements can be expected if the blades are controlled locally, i.e. by dynamic airfoil deformations at blade sections of high aerodynamic efficiency. The latter concept has advantages if detailed flow events like dynamic stall on the retreating blade or transonic effects on the advancing blade are to be influenced favorably. The efficiency of such on-blade control concepts has recently been demonstrated by a nose-droop device acting under dynamic stall conditions.Addressing on-blade control concepts DLR-Goettingen has developed a set of necessary comprehensive numerical and experimental tools to investigate the unsteady aerodynamics about moving and deforming rotor airfoils and blades. These tools include design procedures to define the suitable shapes of rotor airfoils and blades, the time-accurate calculation of unsteady flows by CFD-codes and experimental tools and wind tunnel facilities to measure instantaneous pressure distributions and complete flow fields about oscillating blade models. In the present paper the main tools already available at DLR-Goettingen are described in detail