CFD/CSD Coupling for Camber Morphed Rotor Blades

This paper presents a modular and extensible CFD/CSD loose coupling approach that was developed for passive and active rotor blades. The aerodynamic loads were computed with the CFD solver TAU. The blade motion during the CFD simulation was determined by the CSD solver CAMRAD II, including a trim calculation and blade dynamics calculation. The capability of this CFD/CSD coupling approach was demonstrated by means of a passive and an active single-bladed isolated rotor operated at an advance ratio of μ=0.15. The active section was integrated between 25% and 95% of the rotor radius, also comprising a linear transition region from passive to fully active section of the rotor blade inboard and outboard,respectively. In chordwise direction, the dynamic camber morphing extended from 75% of the chord to the trailing edge. A non-harmonic actuation schedule was applied which yielded a reduction in required rotor power in a previous comprehensive analysis study. The results obtained with the CFD/CSD coupling approach were verified with stand alone comprehensive analysis results(CAMRAD II) using free wake and linear inflow models. The results from CFD/CSD and free wake simulations were in good agreement when comparing the thrust distribution for both passive and active rotor blades. The linear inflow based computations resulted in greater peak loads near the blade tip on the retreating side. The dynamic morphing led to a redistribution of the thrust over the rotor disk and, in particular, an offloading of the blade tip and higher loading in the region where high camber deflections were applied. The developed CFD/CSD coupling framework was demonstrated to be suitable for the investigation of active camber morphing on helicopter rotors.