Modelli aerodinamici per lu27analisi della stabilit? aeroelastica di veicoli propulsi ad elica

摘要

The present PhD Thesis is focused on the development of theoretical and numerical aerodynamic models devoted to the aeroelastic stability analysis of innovative complex propeller-based propulsive systems for aircrafts and ships. Specifically, considering propulsive configurations in which the propeller is mounted on a flexible structure (such as a wing in Tiltrotor airplanes or a strut/gondola in a marine podded propulsor), the main result of this work is a general methodology for the identification of a periodic-coefficient reduced-order model (ROM) for the prediction of unsteady aerodynamic loads on the propeller. It is a state-space model that is based on an approximation of a frequency domain aerodynamic solution and it relates the motion of a propeller/fixed-wing system with blade aerodynamic forces. In addition to simple quasi-steady and unsteady aerodynamic 2D solutions, a fully unsteady 3D solver for potential flows around complex interacting rotating/fixed bodies is herein used as kernel of the ROM model in order to enhance accuracy of the numerical predictions with reduced computational effort. This ROM model is coupled with suitable structural modelling of a propeller/pylon/wing system of a Tiltrotor airplane in order to derive a simple and efficient mathematical description that is very well suited for control applications and aeroelastic analyses in the preliminary design phase. Validation exercises using the developed numerical tools to predict rotor/pylon whirl-flutter and rotor/pylon/wing aeroelastic stability margins are successfully performed in the thesis.