Nonlinear Aeroelasticity of a Very Flexible Blended-Wing-Body Aircraft

This paper presents a study on the coupled aeroelastic/flight dynamic stability and gust response of a blended-wing-body aircraft that derives from the U.S. Air Force's High Lift-Over-Drag Active (HiLDA) wing experimental model. An effective method is used to model very flexible blended-wing-body vehicles based on a low-order aeroelastic formulation that is capable of capturing the important structural nonlinear effects and couplings with the flight dynamic degrees of freedom. A nonlinear strain-based beam finite element formulation is used. Finite state unsteady subsonic aerodynamic loads are coupled to all lifting surfaces, including the flexible body. Based on the proposed model, aeroelastic stability is studied and compared with the flutter results with all or partial rigid-body degrees of freedom constrained. The applicability of wind-tunnel aeroelastic results (where the rigid-body motion is limited) is discussed in view of the free-flight conditions (with all 6 rigid-body degrees of freedom). Furthermore, effects of structural and aerodynamic nonlinearities as well as wing bending/torsion rigidity coupling on the aircraft characteristics are also discussed in this paper.