In comparison with the flutter problem of the elastic wing in case of a fixed wing aircraft, there are additional coupling mechanisms consisting of rotating parts for the rotor blade flutter in rotor craft. For hinged rotor blades, the classical bend-torsion coupling is the most important. On the other hand, for mount-less rotor concepts, flutter mechanisms can also occur by coupling of the bend shapes in the lead and lag directions through rotational effects with following kinematic changes of the blade angulation. By placing the centre of mass of the individual sections at the aerodynamic pressure point on the blade axis and additional mechanical lead damping, the rotor blade is generally not flutter critical. Nevertheless, the lack of flutter must be examined for new blade shapes and rotor concepts. This requires the exact mapping of the stiffening and gyroscopic coupling effects for the mechanical system as well as the retroactive effect of the rotor trail on the unsteady aerodynamic forces on the rotor in hover and forward flight.
To analyse the aeroelastic behaviour of the rotor of rotor crafts, a CFD/MKS coupling using the coupling software PyCSM with MKS SIMPACK, developed by the Institute, and the flow solver TAU, was built for the STELAR project. The first application was to determine blade deformation for the isolated rotor of the ERATO-configuration in hover flight, as is shown in the above figure in the CFD-model, which was coupled with the structural model.