Aeroelastic analysis of a flexible airfoil with a freeplay non-linearity

Abstract

A two-dimensional flexible airfoil with a freeplay non-linearity in pitch has been analyzed in the subsonic flow range. Structurally, the airfoil is modelled as finite beam elements and two spring elemens in pitch and plunge. A doublet lattice method is used for the two-dimensional unsteady aerodynamics to include the camber deflection effect. The fictitious mass modal approach is adopted in order to use the consistent modal co-ordinates for the structures with non-linearity. Non-linear aeroelastic analyses for both the frequency domain and time domain are performed for rigid and flexible airfoil models to investigate the flexibility effect. Results are shown for models of different pitch-to-plunge frequency ratio. Responses involving limit cycle oscillation and chaotic motion are observed and they are highly influenced by the pitch-to-plunge frequency ratio. (C) 1996 Academic Press Limited