Validation of a Finite Element Analysis of a Flapping Wing Against Inertial and Aeroelastic Responses

摘要

Small unmanned aerial systems are being designed to emulate the flapping kinematics of insects and birds which show superior control in slow speed regimes compared to fixed wing or rotorcraft aircraft. The flight of flapping wing vehicles is characterized by aeroelastic effects because wing membranes are highly flexible. The large deformations influence aerodynamics in a significant manner and predicting deformations is essential for evaluating design in early phases. Most research has been dedicated towards understanding the aerodynamic side of the aeroelastic response with minimal effort spent towards validating the structural response. Finite element simulations of a commercial flapping wing are tuned via modal testing and compared to vacuum data to isolate the inertial response. Wing tip displacement amplitude was matched to within 8%. The finite element solver predicted less membrane bellow than observed. Billow in the vacuum was also more asymmetric. Modeling the wing membrane dynamics proved to be difficult because of the high sensitivities associated with the flexible membrane. Additional work is shown on capturing the wing shape during flapping. In the other direction, observed wing billow could be used to predict aerodynamic forces. This research shows that significant focus must be placed on validating the structural side of a flexible structure in order to correctly model the complete aeroelastic response.