Influence of Wing-Propeller Aerodynamic Interactions on Aeroelastic Damping

This paper investigates the influence of wing-propeller aerodynamic interactions on the aeroelastic damping of a wing-propeller system. The system is modeled in the Rotorcraft Comprehensive Analysis System using the viscous vortex particle method for the propeller aerodynamics and the uniform inflow model for the wing. The aeroelastic damping characteristics are identified from simulated time-history data using a recently developed method that captures amplitude effects due to system nonlinearity. The damping characteristics identified using conventional methods based on linear assumptions are also presented for comparison. The results show that, at lower airspeeds, the local damping decreases with increasing propeller hub displacements, both with and without aerodynamic interactions. This amplitude-dependent behavior cannot be captured by conventional damping identification methods that average amplitude effects. Amplitude-dependent trends are exacerbated by wing flexibility. However, they become slight as the system approaches flutter, resulting in linear behavior close to the stability boundary. For a flexible wing, wing-propeller aerodynamic interactions destabilize the system. The impact of aerodynamic interactions on local damping decreases with larger propeller hub displacements, which might be attributed to the skewness of the propeller wake and the extent of its wash over the wing.