Data Driven Parametrization for Flexible Airfoils and Predictive Aerodynamics

NASA achieved an important milestone in aircraft design the past year by flight testing a shapeshifting wing. The design moved the rear region of the wing through large deflection to provide flap operation for takeoff and landing. The next step is inflight surface modification of the entire wing. Underlying the three dimensional wing is the two-dimensional airfoil shape that anchors the wing aerodynamic performance. Many parametric definition of airfoils have been used for optimizing airfoil and wing aerodynamics but these analysis were made for fixed wing configurations. For flexible airfoils, it is important to recognize that the lofting of shapes in flight will happen around a parent airfoil. From a practical perspective it is likely that only a narrow range of shapes will be possible because of limited actuator locations. With this in mind a new Bézier parameterization scheme is introduced that can reproduce current airfoils with the assurance that original aerodynamics is maintained if not improved. Two Bézier curves are used to define the airfoil. One for the top surface and the other for the bottom surface. It is shown that this parametrization lends itself to fixed abscissa placement of control points for all airfoils, identifying possible actuator locations. Bézier curves change globally to local variation in geometry so a few points can generate an effective flexible airfoil. Coupling these changes with a simple analysis program can easily generate aerodynamic sensitivity information to physical shape changes based on the changes in a limited set of control points. This will provide the ability to create a shape based on a new aerodynamic demand while in flight. This paper presents the development of the parameterization scheme only.