Bioinspired, Adaptive, and Self-Deploying Flaps for Distributed Aerodynamic Flow Control

下一代微型和鸟级无人机（uav）必须在非定常环境中航行并进行快速机动。在可能使无人机效率低下和不稳定的相同操作条件下，鸟类和昆虫不仅能够保持高空，而且还可以保持其空气动力学效率。受鸟类翅膀上的羽毛系统的启发，这项工作将使一种流动控制技术能够被动地适应和改变非稳态流动现象。当前的流量控制策略涉及相对较重的设备，这些设备必须主动供电，并且需要昂贵且复杂的流量信息。相比之下，羽毛启发的效应器不需要额外的功率来部署，而且它们对非定常流现象的被动响应能力提供了一个引人注目的低重量、自适应和简单的流动控制范例。控制这个效应系统的基本流动物理将被解释，使其能够在未来的空气动力飞行器中使用。这项工作的生物启发性质为STEM培训、招聘和推广提供了一个绝佳的机会。这项工作的更广泛影响包括大学水平的培训（通过本科生和研究生指导以及课程开发）和K-12外展（通过针对代表性不足的少数民族学生的夏季工程研讨会）。高保真模拟和一个典型系统的详细实验涉及一个翼型与效应器铰接在根部通过扭转弹性弹簧将进行。这种效应系统构成了一个鲜为人知的流固相互作用（FSI）问题。襟翼动力学将与剪切层和尾迹动力学相关，并量化这种相互作用对不同襟翼参数、翼型迎角和雷诺数下气动性能的影响。模拟将在低雷诺数下进行，Re = 1000，与微型无人机和昆虫飞行有关。实验将在更高雷诺数下进行，Re≈200,000，与鸟级无人机和鸟类飞行相关。在这一雷诺数范围内，将首先研究零刚度扭转弹簧铰接的单个襟翼，并将被动襟翼动力学与剪切层动力学、近体和尾流涡动力学以及气动力相互关联。然后，将研究这些FSI物理如何受到有限刚度扭转弹簧的影响，并将任何变化与弹性襟翼系统相关的共振和非共振机制联系起来。最后，将研究一个多襟翼系统，以确定在FSI设置下多个襟翼如何相互作用以改变所产生的气动力。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Next-generation micro- and avian-scale unmanned air vehicles (UAVs) must navigate unsteady environments and undergo rapid maneuvers. During the same operational conditions that may render UAVs inefficient and unstable, birds and insects are not only able to remain aloft, but can also maintain their aerodynamic efficiency. Inspired by a system of feathers on a bird’s wing, this work will enable a flow control technique that can passively adapt to and alter unsteady flow phenomena. Current flow control strategies involve relatively heavy devices that must be actively powered and require costly, complex information about the flow. In contrast, the proposed feather-inspired effectors do not require additional power to be deployed, and their ability to passively respond to unsteady flow phenomena offers a compelling low-weight, adaptive, and simple flow control paradigm. The fundamental flow physics that govern this effector system will be explained to enable its use in future aerodynamic vehicles. The bio-inspired nature of this work presents a prime opportunity for STEM training, recruitment, and outreach. Broader impacts of this work include university level training (via undergraduate and graduate student mentoring as well as course development) and K-12 outreach (via summer engineering workshops targeted towards underrepresented minority students).High-fidelity simulations and detailed experiments of a canonical system involving an airfoil with effectors hinged at the root via a torsional elastic spring will be performed. This effector system constitutes a poorly understood fluid-structure interaction (FSI) problem. The flap dynamics will be related to the shear layer and wake dynamics and quantify the impact of this interplay on aerodynamic performance for different flap parameters, airfoil angles of attack, and Reynolds numbers. Simulations will be carried out at low Reynolds numbers, Re = 1,000, relevant to micro UAVs and insect flight. Experiments will be conducted at higher Reynolds numbers, Re ≈ 200,000, relevant to avian-scale UAVs and bird flight. Over this range of Reynolds numbers, a single flap hinged with a zero-stiffness torsional spring will be first studied and the passive flap dynamics to the shear layer dynamics, near-body and wake vortex dynamics, and aerodynamic forces will be corelated. Then, it will be examined how these FSI physics are affected by a finite stiffness torsional spring and relate any changes to resonant and non-resonant mechanisms associated with the elastic flap system. Finally, a multi-flap system will be studied to determine how multiple flaps interact in this FSI setting to alter the resultant aerodynamic forces.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.