Kinematic Variation and Modeling for Design in Ornithoptic Flight

During soaring forward flight, larger birds such as raptors generate most of their lift in a manner consistent with the lift generated by fixed-wing aircraft. However, in flapping flight there is an additional flow field that must be superimposed to account for thrust generated. The aerodynamic forces can be analyzed using conventional strip theory techniques and integrated across the wingspan and over the entire flapping cycle. Oscillating wing pitch causes the lift vector to contribute to forward thrust and effects useful angles of attack. This paper seeks to predict which kinematic parameters of flapping flight will allow for sustained forward flight. Using a mathematical model for flapping flight and a genetic algorithm, kinematic parameters are selected that provide sufficient lift and thrust while attenuating aerodynamic power consumption. The results show that separate degrees of freedom are necessary for twisting and heaving motions to yield acceptable flight conditions.