Active Control for Transition Delay of Two Dimensional Boundary Layers in In-Flight Experiments

减少飞机表面摩擦仍然是一个重要的经济和环境问题；然而，实现这种减排的积极方法仍然需要大量的研究和开发工作，以达到工业成熟。即使是非常基本的问题，如最合适的概念，执行器或可实现的效率，仍然是开放的讨论。正是在这种背景下，本项目提出应用等离子体致动器来调用二维边界层中的过渡延迟，在实验室中，但特别是在飞行中。以前的研究已经证明了实现过渡延迟的两个基本原则；边界层的稳定和有源波的对消，在四种不同的工作模式下得到了应用。许多这些前体实验都是在简单的风洞实验中进行的；然而，也非常精心和复杂的飞行运动与研究所的机动滑翔机已经证明延迟自然发生的过渡。这项非常广泛的初步工作强调了等离子体作动器在飞机主动控制方面的巨大潜力。提出的工作方案将风洞中平板和翼型的一般构型的理论、数值和实验研究与飞机实际条件下的实验复杂地交织在一起。边界层方程的数值解，连同实验确定的等离子体致动器引起的体力，允许理论上的稳定性分析，以协助配置致动器系统和阵列，以实现高效的过渡延迟。这种预先的设计和优化，然后通过风洞平板实验进行验证和改进。随后在全尺寸机翼手套上进行的风洞实验可以直接进行飞行实验。分析等离子体致动器的功率、有效性和诱导力的新方法将用于评估能量平衡方面的各种操作模式，从而产生总体效率的估计。这是为了直接预测等离子体驱动在未来应用的可行性。

Reduction of skin friction on aircraft remains an economic and environmental issue of importance; however, active methods to achieve such reductions still require significant research and development efforts to reach industrial maturity. Even very basic questions regarding the most appropriate concept, actuator or the achievable efficiency are still open for discussion. It is within this context that the present project proposes the application of plasma actuators to invoke transition delay in two-dimensional boundary layers, in the laboratory, but especially in-flight. Previous studies have demonstrated two basic principles for achieving transition delay; a stabilization of the boundary layer, and the active wave cancellation, which have been used in four different operating modes. Many of these precursor experiments have been conducted in simple wind tunnel experiments; however also very elaborate and intricate in-flight campaigns with the institute's motorized gliders have demonstrated delay of naturally occurring transition. This very extensive preliminary work underlines the enormous potential of plasma actuators for active control on aircraft.The proposed work program intricately interweaves theoretical, numerical and experimental studies of generic configurations of flat plates and wing profiles in wind tunnels with experiments under realistic conditions on aircraft. Numerical solutions of the boundary-layer equations, together with the experimentally determined body force invoked by the plasma actuators, allow a theoretical stability analysis to assist in configuring actuator systems and arrays for energy efficient transition delay. This up-front design and optimization is then to be verified and improved using flat plate experiments in wind tunnels. Subsequent wind tunnel experiments on a full-scale wing glove can then be directly followed by in-flight experiments. Novel approaches for analyzing the power, effectiveness and induced forces of plasma actuators will then be used to evaluate the various operating modes in terms of energy balance, yielding estimates of overall efficiency. This is intended to provide a direct prognosis of how viable this application plasma actuation is in the future.