Measurement and analysis of aerodynamic forces of an Ornithopter in free flight

Abstract

This paper presents an experimental approach to measure the aerodynamic forces acting on an ornithopter during free flight. An ornithopter is a mechanical replica of a bird which flies by flapping its wings. Lift and thrust is solely produced from the flapping of the wings but unlike a fixed wing aircraft, the aerodynamic forces and moments vary with time. The overall effect of these time varying forces affects the kinematics of the vehicle and essential to understand the same to develop such a vehicle into bio-mimicking stealth surveillance UAV carrying a camera. Theoretical analysis has been done and compared with some existing methods for a given wing with a given flapping kinematics. Force measurements on an ornithopter are also carried out in a wind tunnel but since the model is rigidly fixed to the force transducer, the combined effect of the aerodynamic forces due to the movement of the vehicle while flight is obscured.