Meeting Abstract
Gliding has evolved numerous times in different lineages of animals, from lizards, squirrels, and frogs, to more unexpected species like ants and snakes. All gliders convert potential energy to kinetic energy, but there seems to be little commonality in the body plans and force-producing structures across all gliders. This makes identification of salient glide parameters and interspecies comparison difficult. Here we aim to discover a common dynamical framework for gliding in order to answer the question, what role does equilibrium play for animal gliders? We construct a reduced-order model of gliding that captures the large-scale features of the motion seen in a velocity-polar diagram, using force coefficients and launch velocities from experimental glide data as model inputs. By non-dimensionalizing the equations of motion, we find a common set of equations that we analyze via a dynamical systems approach. We look for equilibrium points, their stability, and other phase space structures that affect glide dynamics. For our analysis, we compare theory to experimental data from flying snakes (Chrysopelea) and northern flying squirrels (Glaucomys). The model shows that different gliding modes are possible in the velocity-polar space, even though the glide paths look similar in both theory and experiments. We attribute this to intricacies in the lift and drag curves and how pitch affects equilibrium glide angles. This suggests that natural gliders have more velocity-space complexity than shown in previous studies. This research was partially supported by NSF 1351322 to JJS, NSF 1150456 to SDR, and an NSF IGERT training grant (0966125) for IJY.
