Influence of nonlinear aerodynamic effects on high aspect ratio aircraft model

This paper studies the influence of stall effects and follower forces on High Aspect Ratio (HAR) aircraft model for different load cases and aircraft flexibility levels. The Modeling and Simulation Group Toolbox created by the Chair of Flight Mechanics, Flight Control and Aeroelasticity of Technical University Berlin (ModSiG-FMRA) is used for modeling and analyzing the aerodynamic nonlinearities on the TU-Flex aircraft model. TU-Flex is a scaled flight demonstrator embodying a HAR transport aircraft configuration with modular construction, allowing different flexibility levels (for instance, in this paper a flexible and very flexible set). The ModSiG-FMRA framework uses mean axes formulation, modal uperposition for structural dynamics, therefore considered linear, nonlinear flight mechanics, and quasi-steady or unsteady strip theory for incremental aerodynamics due to elastic deformations. The aerodynamic formulation permits to incorporate stall effects and/or follower forces. The follower forces effect does not show an influence on the load cases simulations of the TU-Flex flight envelope while considering geometrically linear structure. On the other side, stall effects influence the TU-Flex dynamic behaviour by the coupling rigid body and structure, not captured by linear aerodynamics formulations. This coupling mechanism is emphasised by increasing the flexibility level.