Study of Vortex Structures in 3D Unsteady Aerodynamics using Experiment and Simulation

涡旋结构是非定常空气动力学最吸引人的方面之一。动态失速中的前缘涡流(在直升机和风力涡轮机上可见)会导致剧烈振动和机械故障。另一方面，前缘涡(LEV)被认为是昆虫高升力飞行的唯一原因，也是使用三角翼的飞机提供高升力的唯一原因。在昆虫飞行和三角翼上，都可以看到翼型上固定的前缘涡。这是非常有趣的，就像在2D空气动力学中，可以从数学上证明稳定的水平不存在，它会倾向于在弦上对流。然而，在3D中，可以看到这种静止的Levs，它们存在的条件并不清楚。实验和CFD方法已经揭示了3D中的涡旋结构，但由于时间和费用的考虑，这些方法不能用于研究参数空间和识别存在这种有利的Levs的条件。Kiran Ramesh发展了一种降阶离散旋涡方法，可以模拟前缘旋涡，但同时计算成本较低。在本项目中，建议将该方法与涡格法相结合，以便将其扩展到3D。利用这种方法，将研究一系列机翼运动学和平面形状，以分析非定常涡流行为，并确定可能存在静止低涡的条件。将进行实验工作，以支持降阶方法的开发，并利用格拉斯哥大学的亚音速风洞设施进行验证。一系列通用型号配置将使用先进的流动诊断技术(粒子图像测速仪、压敏涂料、3D LDA等)和6分量平衡进行测试。

Vortical structures are amongst the most fascinating aspects of unsteady aerodynamics. Leading-edge vortices in dynamic stall (seen on helicopters and wind turbines), result in violent vibrations and mechanical failure. On the other hand, leading-edge vortices (LEVs) have been credited for being solely responsible for high-lift flight in insects and for providing high lift on aircraft employing delta wings.In both insect flight and on delta wings, a stationary leading-edge vortex on the airfoil is seen. This is very interesting, as in 2D aerodynamics, it can be mathematically shown that a stable LEV cannot exist and that it would tend to convect over the chord. In 3D however, such stationary LEVs are seen, and the conditions under which they exist are not clear. Experiments and CFD methods have shed some light on vortical structures in 3D, but because of time and expense considerations, these methods cannot be used to study the parameterspace and identify conditions where such favourable LEVs exist.Dr. Kiran Ramesh has developed a reduced-order discrete vortex method which models leading-edge vortices, but at the same time is computationally inexpensive. In this project, it is proposed to combine this methodology with a vortex-lattice formulation, so as to extend it to 3D. With the method thus developed, a range of wing kinematics and planform shapes will be studied to analyse unsteady vortical behaviour, and identify conditions where stationary LEVs may exist.Experimental work will be conducted to support the development of the reduced-order method and for validation, using the University of Glasgow's subsonic wind tunnel facilities. A range of generic model configurations will be tested using advanced flow diagnostics (Particle Image Velocimetry, Pressure Sensitive Paints, 3D LDA etc) and a 6 component sting balance.