The aeroelastic response and stability of hingeless rotor blades in hover are investigated using both refined structural and aerodynamic models. Finite elements based on a large deflection-type beam theory are used for structural analysis. No kinematical limitations are imposed on the magnitude of displacements and rotations in the strain-displacement relations. Various two-dimensional strip theories and a three-dimensional aerodynamic theory are used to evaluate the aerodynamic loads. Three-dimensional aerodynamic model, based on the unsteady vortex lattice method with a prescribed wake geometry, can predict the unsteady airloads of multi-bladed rotors and the effect of the interblade unsteady wake dynamics beneath the rotor blades on the aeroelastic response.
In the two-dimensional case, numerical results of the steady deflections and stability boundaries are compared with those based on the previous moderate deflections theories. The agreement between two results is good except at very high thrust levels where the structural modeling, which is valid for large deflections, is required. In the three-dimensional case, it is found that the three-dimensional aerodynamic tip-relief and unsteady wake dynamics effects, not predicted in the two-dimensional strip theory, play an important role in the hingeless rotor aeroelastic analysis in hover.
