Far from Cruise: Avian Flapping-Flight Dynamics

Avian flight is so much more than just steady, level cruise. Some birds bound intermittently while they fly, and others dive while capturing prey. Some even fly upside down! This work describes the development of a theoretical model that can simulate these far-from-cruise conditions, and offers a pathway for future research into animal flight dynamics.
Recently, predictive simulation methods have been used to derive power-optimal wing motions in hover and cruise. The model developed here follows a similar philosophy, but extends the context to modes of flight that feature significant accelerations of the body. This includes both linear accelerations, such as in breaking flight, and rotational accelerations, as seen in pull-up and pushover manoeuvres. The model provides insight into how birds induce such extreme, yet graceful, dynamics using the flight apparatus available to them. Results from the model are presented as a series of animated flight trials, each focussing on a mode of flight that is observable in nature. The predictive methodology determines plausible wing and tail kinematics and also indicates the energetic cost of undertaking these different modes.