UNSTEADY AERODYNAMIC REDUCED-ORDER MODELS FOR THE ANALYSIS OF PROPROTORS WHIRL FLUTTER INSTABILITY

This work deals with the aeroelastic modeling for the analysis of whirl flutter instability, that is one of the limiting factors to cruise velocity for tiltrotors. The emphasys is on the examination of the influence of the accuracy of the aerodynamic model included in the analysis, with particular attention to those models that can conveniently be applied to preliminary design and control purposes. To this aim, a methodology for deriving reduced-order models from aerodynamic unsteady solvers is used. Considering a simple pylon/proprotor structure, whirl flutter boundaries are identified by applying reduced-order models obtained both from the 2D Loewy/Greenberg theory, and from a 3D unsteady, potential flow BEM solver. Results from the quasi-steady aerodynamics model are included for comparison.