Abstract: An air vehicle trying to operate in adverse weather or wakes of urban canyons and mountainous terrains would be hit by strong large-scale atmospheric disturbances. In such extreme aerodynamic conditions, flight control becomes a great challenge, if not impossible, due to the enormous transient forces that the vehicle experiences. Currently, encounters with these extreme flow phenomena limit operations of fixed and rotating wing aircraft, especially those that are small to medium in size. The present study is focused on the analysis, modeling, and control of extreme aerodynamic flows, with unsteadiness far larger in amplitudes than those considered in traditional aerodynamics on a time scale comparable to that of the flow instabilities. A major challenge with extreme aerodynamic problems is the complete lack of theoretical foundation and a unified perspective to tackle such complex nonlinear problems. The high-dimensionality, strong nonlinearity, and multi-scale properties of these extreme flows make effective analysis and control a tremendous challenge. Without the reduction of the state variable dimension and extraction of dominant dynamics, the application of dynamical systems and control theory for flow control remains a difficult task. Our research group focuses on developing physics-based approaches to model and control complex fluid flows by leveraging data-driven techniques and high-performance computing. Equipped with these toolsets, we extract essential dynamics to facilitate the development of sparse and reduced-order models to design flow control techniques for high-dimensional unsteady fluid flows. We discuss some of the challenges and successes in characterizing, modeling, and controlling extreme aerodynamic flows for lifting surfaces.
This work is supported by the Vannevar Bush Faculty Fellowship and the Air Force Office of Scientific Research.