Applying multi-objective variable-fidelity optimization techniques to industrial scale rotors: blade designs for CleanSky

Abstract

A novel variable-fidelity multi-objective optimization technique is applied to the design problem of helicopter rotor blades of the Green RotorCraft research programme of CleanSky. The optimization technique utilizes information from aerodynamic low-fidelity tools, here a prescribed wake model in forward flight and inviscid CFD simulations in hover, to speed-up the high-fidelity optimization, which is based on RANS simulations including all five-rotor blades. In reference to a state-of-the-art single-fidelity optimization, this approach finds about 325% more viable data points. A choice of three rotor blades from the final Pareto frontier of the optimization is investigated in detail including the off-design performance as well as acoustic footprint in an overflight condition. The final outcome is that there does not exist one blade that fully satisfies all criteria at once, but feasible trade-offs are found when applying the variable-fidelity multi-optimization technique.