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

University Of Illinois At Urbana-Champaign, Urbana IL

Investigators

Abstract

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.