Nonlinear Aeroelasticity and Unsteady Aerodynamics

气动弹性学科关注的是柔性结构与其周围流体的相互作用。结构周围的气流对结构产生作用力。如果结构是柔性的，它就会因这些载荷而变形，随后这种变形会改变流动，以此类推，直到达到某种平衡状态。一个例子是飞机机翼在进入大气湍流区域时的振动，或者对一股阵风的反应。这非常类似于当一阵风吹过窗户时百叶窗的抖动动作。气动弹性运动的许多方面是众所周知的。然而，其他许多项目仍然存在问题。例如，机翼的持续振荡可能发生，有时没有明显的外部原因。其他时候，原因是已知的，但很难建立模型，因此很难预测和控制。这些振荡可能对飞机的性能和安全造成严重后果。飞行的昆虫和鸟类由于其灵活的翅膀也经历了流体-弹性相互作用。然而，这些相互作用通常对动物的飞行能力有积极的影响。这些气动弹性振荡的另一个好处是它们在能量收集方面的潜在用途。本研究旨在通过一系列简单到复杂的模型来理解这些流体-弹性相互作用现象。它主要集中在低空速飞行制度，这是非常适合无人驾驶飞行器（UAV），更大的和非常灵活的高空长航时（HALE）飞机和风/流体动力能量采集器

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.**