Nonlinear Aeroelastic Study of Bending Divergence

In the beginning of the history of aviation, aeroelastic static instabilities were a problem in operating monoplane aircraft. After being discovered, they have been systematically avoided by design, since they would have led to large deformations and structural failure. A new research trend (active aeroelasticity) reverts this approach and utilizes — instead of avoiding — static instabilities to realize wing morphing. Another modern research trend are compliant systems (i.e. structures designed to achieve large deformations within its elastic range). Joining those two trends lead to a novel class of airfoil structures (compliant, active aeroelastic wings) enables operating at and beyond aeroelastic instabilities. Such structures need a new modeling approach, which includes nonlinearities of structural and aerodynamic kind. In this paper, a non linear analysis of aeroelastic bending divergence (a phenomenon which concerns forward-swept wings) is presented, initially based on so-called low-fidelity models. Such models are to some extent inaccurate, but allow a good insight into the physical behavior of the phenomenon. Experimental tests of a compliant airfoil will then be presented, performed to investigate the trans-critical and post-critical response of the airfoil model and to validate the low fidelity models. At the end, high-fidelity modeling is approached, which makes use of computational numerical simulations methods (FEM, CFD, FSI). Selected results will be presented, which allow to predict the system response more accurately and to reproduce the wind tunnel test results more closely.