Study of vortex stability in swept wing configurations using theory, experiment and simulation

后掠翼平台能够在飞机和无人机中实现高度灵活和高升力的飞行。这种平面上最重要的流动特征是非定常前缘涡(LEV)，它是由于流动与机翼边缘分离而产生的。这在机翼的吸力侧创造了一个低压区域，从而实现了高升力和操纵性。然而，狮子座容易受到不稳定因素的影响，这可能会导致涡旋破裂。更好地了解不稳定以及开发流量控制方法来缓解或消除它们，可能有助于扩大基于三角翼的无人机和飞机的飞行范围。该项目旨在开发新的解析和低阶数值方法来表示后掠翼布局上的涡基飞行。该研究的创新之处在于从完全非定常的意义上研究流动，并基于流动中的临界点(如半鞍点、满鞍点和结点)建立系统的动力学模型。为了支持理论和数值模型的发展，我们将通过实验系统地研究三维LEOS中的临界点。实验工作将利用格拉斯哥大学的亚音速风洞设施进行。将使用先进的流动诊断技术(立体粒子图像测速仪、烟雾流动可视化、3D激光多普勒测速仪和非稳定压敏涂料)和6组分平衡。将特别寻找涡旋增强、破裂和轨迹的位置和特征。该实验装置包括一个定制的俯仰俯仰俯冲装置，该装置由三个通过LabVIEW控制的线性执行器组成，用于创建不同的运动以研究前沿分离的瞬变CFD模拟(使用内部OpenFOAM植入)，还将用于相互验证实验和支持模型开发。进一步了解Levs之间的相互作用机制将使机翼设计得更高效、更安全。了解不同类型的稳定级别构型存在的条件将有助于避免和控制涡旋破裂事件，并使安全运行在有利级别存在的条件范围内。利用所获得的知识，将在项目的最后阶段研究维持稳定旋涡的流动控制。将考虑被动(涡旋产生器、表面粗糙度元素)和主动(吸气/吹气、等离子体激励器)策略。

Swept wing planforms enable highly-agile and high-lift flight in aircraft and UAVs. The most important flow feature on such planforms is the unsteady leading-edge vortex (LEV) which is created owing to flow separation from the edges of the wing. This creates a low-pressure area on the suction side of the wing, enabling high lift and maeuverability. LEVs however are subject to instabilities which could lead to vortex breakdown. A better understanding of the instabilities and the development of flow-control methods to alleviate or eliminate them could contribute to an extension of the flight envelope in delta-wing based UAVs and aircraft. This project aims to develop new analytical and low-order numerical methods for representing vortex-based flight on swept-wing configurations. The novel aspects of the proposed research are to study the flow in a fully unsteady sense, and to develop a dynamical model for the system based on critical points (such as half saddles, full saddles and nodes) in the flow. To support the development of theoretical and numerical models, the critical points in 3D LEVs will be systematically studied using experiments. Experimental work will be conducted using the University of Glasgow's subsonic wind tunnel facilities. Advanced flow diagnostic techniques (stero-Particle Image Velocimetry, smoke flow visualisation, 3D Laser Doppler Anemometry, and unsteady Pressure Sensitive Paints) and a 6 component sting balance will be used. The locations and characteristics of vortex enhancement, breakdown and trajectories in particular will be looked for. The experimental setup includes a custom-built pitch-plunge-surge facility developed that is comprised of three linear actuators, controlled through LabVIEW, to create the different motions to investigate leading edge separation Transient CFD simulations (using an in-house OpenFOAM implmentation) will also be used to mutually validate experiments and to support model development. Further understanding of the interaction mechanisms between LEVs will allow wings to be designed to operate more efficiently and safely. Understanding of the conditions in which different types of stable LEV configurations exist will aid in avoidance and control of vortex breakdown events, and enable safe operation within the envelope of conditions where favorable LEVs exist. Using the knowledge gained, flow control for sustaining stable vortices will be investigated in the final phase of the project. Passive (vortex generators, surface roughness elements) and active (suction/blowing, plasma actuators) strategies will be considered.