Low-order Aeroelastic Modelling of a High Aspect Ratio Wing Aircraft Under Constrained Motion

The work presented in this paper describes the modelling of a low-order aeroelastic solver, built with the aim of analysing the dynamics of very flexible wing aircraft, with a focus on the coupling between the flight dynamics and the structural dynamics. The model implements a geometrically exact, low-order nonlinear beam solver based on beam shape functions coupled with Vortex Lattice Method (VLM), specifically adapted to account for large deformations. The static solution calculated by implementing the VLM was compared with the one calculated using strip theory as aerodynamic solver, showing good agreement in magnitude, but different load distribution. The aeroelastic solver was then used to analyse the dynamics of a flexible aircraft constrained to a circular trajectory with free pitch (resembling the motion on a Pendulum Rig) and on a spherical motion with free pitch and yaw (resembling the motion on the University of Bristol 5-DOF Manoeuvre Rig), for two different values of pitch stiffness and three different flexible wings (5% deflection, 10% deflection and 15% deflection with respect to the wing semispan). The results show that when the stiffness is high, it suppresses any interaction between the flight dynamics and the structural dynamics. Therefore there is no impact of the wing flexibility on the aircraft motion. On the other hand, when lowering the value of the pitch stiffness, the interaction between the wing dynamics and the pitch dynamics become evident. However, the impact of the wing flexibility was found to be always negligible on the yaw dynamics.