Morphlight Theory Inspired by Raptor: Flexible Effects of Flight Feather on Bionic Airfoil Aerodynamic Performances of Aquila Chrysaetos

The flight feather of Aquila Chrysaetos has large flexibility and usually deforms greatly during wing beating, which changes the aerodynamic performances of Aquila Chrysaetos dramatically. However, the flexible effects of flight feather on airfoil aerodynamic performances have not yet been fully conducted, nor the aeroelastic model of flexible feather ever been built. In the current study, the geometry of a wing section with a secondary flight feather of Aquila Chrysaetos was scanned using the tracking laser scanning system to establish the bionic airfoil. The flexibility of the flight feather was measured to obtain the nonlinear beam model. The radial basis function (RBF) mesh motion approach was adopted to dynamically generate the feather mesh with large deformations at each iteration. Thereafter, an aeroelastic approach was established by coupling the CFD method and the structural dynamic systems (CSD) method. In the method, airfoil aerodynamic forces were predicted by the CFD method followed by feather deformation calculations based on the CSD method, and the data was transferred via a fluid-structure interaction interface developed using the multi-point constraint (MPC) approach. Aeroelastic performances of the bionic airfoil with a flexible feather undergoing elastic deformation were simulated by the method proposed. Results showed that feather flexibility has a great influence on aerodynamics. Obtained flexible feather effects and flow mechanisms could be an inspiration for future aircraft design.