A method for nonlinear aeroelasticity trim and stability analysis of very flexible aircraft based on co-rotational theory

Very flexible aircraft with high aspect ratio wings subjected to aerodynamic loads undergoes large deformation, which will lead to distinct changes on the mass distributions, stiffness characteristics and aerodynamic characteristics of the complete aircraft. The aeroelasticity and flight dynamics of such aircrafts are nonlinear and the linear elastic theory model cannot be used. A new method is developed for the analysis of nonlinear aeroelasticity and flight dynamics of very flexible aircraft through combining the co-rotational beam theory with the modified ONERA dynamic stall model. Based on a form of co-rotational technique which is external to the element, a spatial two-node beam element, which depicts the geometrically nonlinear dynamic characteristics of the flexible wing, is developed. Both tangential stiffness matrix and mass matrix of the beam element are formulated to establish the nonlinear dynamic equations. In addition, the modified ONERA dynamic stall model is adapted to evaluate the unsteady nonlinear aerodynamic loading of the very flexible wing. Using the present method, the nonlinear aeroelastic response, trim and stability characteristics of a very flexible aircraft are predicted in this paper. The obtained results show a good agreement to the literature, which indicates that the present method is accurate and efficient.