Shock-wave/Boundary-Layer Interactions (SBLI): Physics and Control

激波/边界层相互作用（SBLI）是未来航空航天系统发展的一个关键研究领域，因为它们在高速气动流动中无处不在。SBLI区域的异常压力和热负荷带来了各种各样的问题，包括航空结构和相关保护系统的损伤/快速疲劳、进口气流畸变和发动机无法启动，所有这些都可能产生不利后果。以往的研究指出，激波/分离区的低频非定常是主要现象，并指出如果不了解非定常，即使是平均性质的行为也不能完全理解。此外，由于所采用的模型的局限性，计算研究发现很难准确地捕捉到sbli的动力学。因此，利用最先进的实验技术对激波/边界层相互作用进行实验研究是至关重要的。该项目的目的是开发一个超音速设施，其中最先进的实验方法可以用来获得定性和定量信息。先进的光学诊断技术，包括粒子图像加速度测量（PIA）和多平面粒子图像速度测量（PIV）将得到发展。高质量的成像测量将与快速响应的表面压力测量一起进行，以表征各种流动配置中冲击波/边界层相互作用的不稳定性和三维性质。测量将在上游超音速边界层、相互作用区和激波诱导分离区进行。这些数据将被仔细分析，目的是建立一个物理框架来解释造成流场不稳定和三维性质的原因。一般的（涡发生器、流槽）和最先进的（压电致动器）控制方案将被用来控制激波非定常的频率和振幅。元件将被驱动并得到相平均速度、加速度和压力场。这些数据将用于了解流量对控制方案的响应，从而有助于开发改进的控制策略。采用闭环方案实现必要的局部控制的可行性也将被探讨。

Shock-wave/boundary-layer interaction (SBLI) is a critical area of research for the development of all future aerospace systems as they are ubiquitous in high-speed aerodynamic flows. The extraordinary pressure and thermal loads in the regions of SBLI poses a wide variety of problems including damage/rapid fatigue to aero-structures and associated protection systems, inlet flow distortion and engine unstart, all of which could have adverse consequences. Previous studies have noted that the low frequency unsteadiness of the shock-wave/separation region as a dominant phenomenon and indicated that even the behaviour of mean properties cannot be fully understood without some knowledge on the unsteadiness. Moreover, computational studies find it difficult to accurately capture the dynamics of SBLIs due to the limitations of the models employed. Therefore, it is vitally important to perform experimental investigations of shock-wave/boundary-layer interaction using state-of-the-art experimental techniques. The aim of this project is to develop a supersonic facility where state-of-the-art experimental methods can be employed to obtain qualitative and quantitative information. Advanced optical diagnostic techniques including Particle Image Accelerometry (PIA) and multiple-plane Particle Image Velocimetry (PIV) will be developed. High-quality imaging measurements will be performed together with fast-response surface pressure measurements to characterise the unsteadiness and the three-dimensional nature of shock-wave/boundary-layer interactions in a variety of flow configurations. Measurements will be obtained in the upstream supersonic boundary layer, the interaction region and in the shock induced separation region. The data will be carefully analysed with the aim of developing a physical framework to explain the causes responsible for the unsteadiness and the three-dimensional nature of the flow field.Generic (vortex generators, streamwise slots) and state-of-the-art (piezo actuators) control schemes will be employed to control the frequency and amplitude of shock-wave unsteadiness. The components will be actuated and phase-averaged velocity, acceleration and pressure fields will be obtained. The data will be used to understand the response of the flow to the control scheme, which in turn can help in development of improved control strategies. The feasibility of employing closed-loop schemes to achieve necessary localised control will also be explored.