Navier-Stokes Prediction of Helicopter Rotor Performance Including Aero-Elastic Effects

Two numerical methods (the DLR code FLOWer and the ONERA code CANARI), based on the resolution of the Reynolds Averaged Navier-Stokes equations, are applied in this paper in order to compute the performance of helicopter rotors in hover. The comparison of computed performance with experimental results of the scale-1 BO-105 rotor and the model 7A rotor assuming rigid blades show a significant overestimation of rotor thrust and power. An easy and efficient way to account for the blades elasticity in torsion is then described. The new aero-elastic computations show much better agreement with experiment, especially for the hingeless BO-105 rotor, even if the rotors figures of merit are underestimated for a given thrust coefficient. It is finally shown that accounting for a laminar-turbulent boundary layer (instead of a fully turbulent boundary layer) in the Navier-Stokes code significantly increases the estimated figure of merit, thus improving the correlation between computations and experiment