Comprehensive Numerical and Experimental Tools at DLR-Göttingen

Abstract

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. These control concepts can only influence the complete rotor blade and therefore have 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 as well as transonic effects on the advancing blade are to be influenced favorably. The effiency of such an on-blade-control concept has recently been demonstrated by a nose-droop device acting under dynamic stall conditions. Adressing on-blade control concepts DLR-Göttingen has developed a set of necessary comprehensive numerical and experimental tools to investigate the unsteady aerodynamics of 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 windtunnel facilities to measure instantaneous pressure distributions and complete flow fields about oscillating blade models. In the following the main tools already available at DLR-Göttingen are described in some detail.