Separation control with Air Jet Vortex Generator arrays in transonic and supersonic flow

激波诱导的流动分离强烈地影响着许多航空航天应用的气动性能，从跨声速机翼和超音速吸气推进到高超声速飞行器的控制面。当压力振荡激发共振频率时，相关的高度非定常流场会导致进口不稳定，以及抖振和结构疲劳。这些流动在航空航天运输中的重要性促使人们作出巨大努力，开发减少分离有害影响的方法。这个Emmy Noether小组研究了一项很有前途的新技术：喷气涡发生器（ajvg）。一组连续的小气流将涡旋插入边界层。涡流携带高动量流体，增加湍流混合，从而减少分离并控制相关的不稳定性。ajvg有很多优点：不像边界层泄油，内部质量流率不会降低。该系统相对简单，但比机械装置更灵活，可以在不需要时关闭，以减少寄生阻力。在生成二维激波/边界层相互作用（SWBLI）的AJVG控制所需的专业知识方面取得了进展。然而，在大多数应用程序中，几何图形和swbli是3D的，因此更加复杂。三维SWBLI对分离控制的响应机制以及有效的控制机制和参数尚不清楚。因此，在本项目阶段，我们继续系统地增加整个项目中所追求的配置复杂性：在名义上的2D相互作用以及随后从侧壁和曲率添加的3D效果之后，我们现在分析AJVG在全3D swbli上的分离控制，即扫描-压缩-斜坡相互作用，以更全面地了解AJVG控制。本项目阶段的核心目标是：1)描述ajvg对三维SWBLI中平均和湍流拓扑结构的影响，并确定控制参数；2)了解ajvg对三维SWBLI机制的影响；3)制定合适的控制策略。这些目标的解决方法结合了尖端的实验技术，高保真数值模拟，和先进的后处理。在上一个项目阶段开发的立体双粒子图像测速（S-D-PIV）系统提供的速度场也包括时间信息。大涡模拟提供了时间分辨的流场和对空气射流的详细见解。结合先进的后处理方案（特别是动态模态分解），最终可以获得湍流结构的行为和流场中的动力机制。通过促进对相关复杂流动的基本理解，艾美·诺特小组参与了为新的令人兴奋的航空航天运输概念和负担得起的太空访问做好准备的工作。

Shock-induced flow separation strongly influences the aerodynamic behavior of many aerospace applications, from transonic airfoils and supersonic air-breathing propulsion to control surfaces on hypersonic vehicles. The associated highly unsteady flow field can cause inlet instability, as well as buffeting and structural fatigue when pressure oscillations excite a resonant frequency. The importance of these flows in aerospace transportation motivated great efforts to develop methods that reduce the detrimental effects of separation. This Emmy Noether group investigates a promising new technique: air jet vortex generators (AJVGs). An array of small continuous air jets inserts vortices into the boundary layer. The vortices entrain high-momentum fluid and increase turbulent mixing, which reduces separation and controls the associated unsteadiness. AJVGs have many advantages: unlike with boundary-layer bleed, internal mass-flow rates are not reduced. The system is relatively simple, yet more flexible than mechanical devices and can be turned off when not needed, to decrease parasitic drag. Progress has been made in generating the required expertise on AJVG control for 2D shock-wave/boundary-layer interactions (SWBLI). In most applications, however, geometries and SWBLIs are 3D and thus more complex. The mechanisms in 3D SWBLI that are responsive to separation control, as well as effective control mechanisms and parameters, are unclear. In this project phase, we therefore continue the systematic increase in configuration complexity pursued in the overall project: after nominally 2D interactions and the subsequent addition of 3D effects from side walls and curvature, we now analyze separation control with AJVGs on fully 3D SWBLIs, namely swept-compression-ramp interactions, to approach a more general understanding of AJVG control. The core goals of this project phase are to 1) describe the influence of AJVGs on the mean and turbulent flow topology in 3D SWBLI and identify control parameters, 2) understand the effects of AJVGs on the mechanisms of the 3D SWBLI, and 3) develop a suitable control strategy. These objectives are addressed with an approach combining cutting-edge experimental techniques, high-fidelity numerical simulations, and advanced post processing. The stereo-dual particle-image-velocimetry (S-D-PIV) system developed in the previous project phase provides velocity fields that also include temporal information. Large-eddy simulations provide time-resolved flow fields and detailed insights into the air-jet flow. Together with advanced post-processing schemes (inter alia dynamic mode decomposition), the behavior of turbulent structures and the dynamic mechanisms in the flow fields are finally accessible. By contributing to the fundamental understanding of the related complex flows, this Emmy Noether group participates in preparing the ground for new exciting aerospace-transportation concepts and affordable access to space.