Enhanced unsteady vortex lattice aerodynamics for nonlinear flexible aircraft dynamic simulation

Several modelling extensions and numerical improvements to the unsteady vortex-lattice method are discussed for the simulation of very flexible aircraft dynamics. In particular, fuselage aerodynamics are included by means of linear source panels, polar corrections are incorporated on the aerodynamics under potentially large deformations, and a new wake discretization scheme is derived to accelerate the computations. The theory behind each approach is detailed and successfully verified on representative test cases. The resulting modelling environment is then exemplified in a study of the flight dynamics of a flexible aircraft demonstrator model. Results indicate that for large wing deformations, a noticeable effect of fuselage aerodynamic interference appears on the wing aeroelastic behaviour. The polar corrections improve the drag estimations and allow capturing lift decrements due to stall onset at high induced angles of attack, which then affects the gust loads. The wake discretisation scheme enables a reduction of the computational time for dynamic simulations on a full aircraft model by about 20 % while keeping the arising error negligible small