使用 Wiener-Hopf 方法对 Tollmien-Schlichting 波进行实验控制
Experimental control of Tollmien-Schlichting waves using the Wiener-Hopf formalism
AI总结：
本文提出使用 Wiener-Hopf 方法对机翼表面的 Tollmien-Schlichting 波进行实验性反应控制，通过在频域构建因果控制核以解决传统波消除技术依赖未来信息的非因果问题，实验证明该控制器能有效减弱波并优于传统方法。
摘要：
反应性流动控制已被证明是一种极具前景的工具，可用于改善飞行器的空气动力学特性等诸多方面。本文重点关注使用反应性流动控制来减弱机翼剖面上的 Tollmien-Schlichting (TS) 波。TS 波是一种不稳定性机制，是边界层向湍流转变的最初阶段之一。本工作采用 Wiener-Hopf 技术进行实验性边界层控制。该方法改进了以往的波消除技术，这些以往技术在频域内构建控制核会导致控制核包含非因果部分，即执行器需要未来的传感器信息才能构建。在实际应用中，获取此类信息是不可行的。忽略核的非因果部分会导致次优解，可能显著降低控制器性能。Wiener-Hopf 方法允许我们在控制问题的表述中考虑因果性约束，从而得出最优的、符合现实的解以及构造上即具因果性的控制核。此外，还可以在数据驱动方法中，仅基于实验获得的功率谱和交叉谱来构建控制策略。本工作展示了如何利用风洞实验信号在实验中应用基于 Wiener-Hopf 预解的方法，证明 Tollmien-Schlichting 波可以通过基于 Wiener-Hopf 的控制器有效减弱，且其效果优于典型的波消除方法。
英文摘要：
Reactive flow control has been shown as a promising tool to improve, among other aspects, the aerodynamic characteristics of an aircraft. This paper focuses on the use of reactive flow control to attenuate Tollmien-Schlichting (TS) waves over a wing profile. TS waves are an instability mechanism that is one of the first stages of boundary layer transition to turbulence. The Wiener-Hopf technique was used in this work for the experimental boundary layer control. The approach improves previous wave-cancellation techniques that, by constructing control kernels in the frequency domain, lead to control kernels with a non-causal part, i.e., actuation would need future sensor information to be constructed. In practical applications, it is unfeasible to access this type of information. Ignoring the non-causal part of the kernel leads to suboptimal solutions that might significantly degrade the performance of the controller. The Wiener-Hopf formalism allows us to take into account causality constraints in the formulation of the control problem, leading to an optimal realistic solution and a control kernel that is causal by construction. Moreover, it is possible to construct the control strategy based only on the power and cross-spectra obtained experimentally, in a data-driven approach. The present work shows how to apply experimentally the Wiener-Hopf resolvent-based formalism using signals from a wind tunnel experiment, demonstrating that the Tollmien-Schlichting waves can be effectively attenuated via a Wiener-Hopf based controller, which yielded better results than a typical wave-cancellation approach.
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