Stability of flapping flight dynamics of large birds
(2022)
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- Abstract
- Birds have inspired human innovation and technology for centuries. The first documented human flying attempt is in the late 800, from Abbas ibn Firnas who created what is considered the first aviation experiment. Later in the years, around the 15th century, Leonardo da Vinci dedicated long time of his research to formally understand bird's flight, leading him to the famous ornithopter invention. Biological fliers are still nowadays a source of scientific inspiration for unsolved research questions. Their capability of flying such a long range during migrations, responding to environmental perturbations and maneuvering are still beyond current engineering advances. This Thesis aims at contributing in the field of flight stability of migratory birds, trying to understand the biological and kinematic parameters that govern flapping flight. From a physical point of view, the flapping motion represents a forcing term in the equations of motion of bird flight. Generally speaking, due to this action, there are no fixed points of equilibrium. The problem of studying stability of bird flight therefore is re-formulated via a limit cycle analysis of such equations of motion. We tackled this problem via a numerical framework that relies on a multiple-shooting algorithm that both detects limit cycles, and assesses their stability via Floquet theory. We provide evidence that the generation and repartition of the pitching moment are the main mechanisms that regulate longitudinal stability. Our numerical results suggest that open loop stability cannot be achieved in absence of the tail surface. The open loop stability can however be achieved introducing the tail surface. Nevertheless we showed that the latter configuration is not ideal for long range flights, both in terms of power consumption and bird's agility. We deduced that to satisfy the observed flight configuration with furled tail, while maintaining stable flight, birds developed biocontrol schemes for continuosly adapting their wing kinematics.
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Citations
Ducci, G. (2022). Stability of flapping flight dynamics of large birds. https://hdl.handle.net/2078.5/103438