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This paper presents a study on aeroelastic analyses of composite laminated wings subject to large displacements through the coupling of a nonlinear corotational shell finite element (FE) with an unsteady vortex-lattice method (UVLM) formulation. A FE implemented for the analysis of flat plates has been extended to model laminated composites with different lamina orientations. An UVLM formulation that is capable of coupling with this large displacement structural model is implemented. An explicit partitioned method is evaluated for the coupling of both models, using spline functions to interpolate information from the structural operator to the aerodynamic one, inside a Generalized-a time-marching solution. The resulting aeroelastic formulation provides a framework for the nonlinear aeroelastic analyses of structures made of composite material allowing the characterization of their nonlinear behavior and simulation of the limit-cycle oscillation response. Flat plate laminated wings designed for high flexibility and low flutter speed onset are used as investigation models. Effects of nonlinearities are easily observed in the numerical results, which are promising for expansion of the work and application to the analysis of more refined and complex composite flexible wings.

The paper addresses further investigations on downwash correction methods for aeroelastic stability analyses in the transonic regime. The main concern is the investigation of the influence of the nature of the lifting surface motion, considering a general elastic body modal displacement to compute unsteady pressures. A finite-difference Navier-Stokes code is used to calculate the unsteady aerodynamic loads due to a three dimensional transonic flow. The unsteady pressure coefficients computed using this code are used as a reference state for flutter analyses based on a linearized aerodynamic theory using the downwash weighting method. The test case considered is the well-known AGARD wing 445.6 standard aeroelastic configuration. The results are compared with previous theoretical investigations.

The paper is concerned with downwash correction methods for aeroelastic stability analyses in the transonic regime. The effects of the formulation used in the calculation of nonlinear, unsteady reference pressures are addressed, together with the influence of the motion amplitude. A finite-difference Euler/Navier–Stokes code is used to calculate the unsteady aerodynamic loading due to dynamic angle of attack variations in three-dimensional transonic flow. The computed unsteady pressure coefficients are used as a reference state for flutter analyses using the downwash weighting method. The test case considered is the well-known AGARD wing 445.6 standard aeroelastic configuration. The configuration is subjected to rigid body pitching oscillation about the mid-chord point at the root section. Flutter boundaries are computed using either inviscid or viscous-based unsteady pressures in the downwash correction methodology. The results are compared with available experimental data and they indicate that both viscous and thickness effects play an important role on the flutter prediction capability.