Unsteady, Motion-Induced Aerodynamic Interaction on Propeller–Wing System

Flutter stability assessment is a key part of propeller aircraft design, and advanced methods are available to model the aircraft and propeller within this analysis. Nevertheless, there is limited knowledge regarding the effect of aerodynamic interaction between the propeller and the wing on motion-induced aerodynamic loads and flutter. This work identifies the key elements of aerodynamic interaction and their influence on generalized aerodynamic forces and flutter. Potential aerodynamic modeling in the time domain is combined with forced-motion identification of unsteady loads in the frequency domain. By identifying transfer functions for propeller and wing individually while exciting either the wing or propeller, the interaction terms can be split into wing-to-propeller and propeller-to-wing interaction. The motion-induced aerodynamic loads are furthermore used to conduct flutter analyses for simple aeroelastic systems to show the effect of interaction on flutter stability. For the wing, steady interaction with the propeller slipstream is shown to have larger influence on unsteady aerodynamics, while for the propeller loads, the dominating interaction components are the unsteady loads induced by the oscillating wing. Despite accounting for interaction, changes in the flutter speed for isolated wing and whirl flutter remain small.