Nonlinear Aeroelasticity and Unsteady Aerodynamics

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The discipline of aeroelasticity is concerned with the interaction of a flexible structure and the fluid it is surrounded with. The flow around a structure induces forces on it. If the structure is flexible, it will deform in response to these loads and subsequently this deformation will modify the flow, and so on until some type of equilibrium state is achieved. An example is the vibrations of an aircraft wing as it enters a zone of atmospheric turbulence, or in response to a single gust. This is very similar to the fluttering motion of venitian blinds when a gust of wind occurs through a window. Many aspects of the aeroelastic motions are well known. Many others are, however, still problematic. For instance, sustained oscillations of a wing can occur, sometimes without apparent external cause. Other times, the cause is known but it is very difficult to model, hence to predict and control. These oscillations may have dramatic consequences on the performance and safety of the aircraft. Flying insects and birds are also experiencing fluid-elastic interactions due to their flexible wings. However, these interactions often have a positive impact on the ability of the animal to fly. Another benefit of these aeroelastic oscillations is their potential use for energy harvesting. This research aims at understanding these fluid-elastic interactions phenomena via a range of models, simple to more complex. It mainly focuses on low airspeed flight regimes, which are well suited to unmanned air vehicles (UAV), larger and very flexible high altitude long endurance (HALE) aircraft and wind/hydrodynamic energy harvesters.