The Dynamics of Non-Equilibrium Gliding in Flying Snakes
| Autor: | Yeaton, Isaac J. |
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| Rok vydání: | 2018 |
| Předmět: | |
| Druh dokumentu: | Dissertation |
| Popis: | This dissertation addresses the question, how and why do 'flying' snakes (Chrysopelea) undulate through the air? Instead of deploying paired wings or wing-like surfaces, flying snakes jump, splay their ribs into a bluff-body airfoil, and undulate through the air. Aerial undulation is the dominant feature of snake flight, but its effects on locomotor performance and stability are unknown. Chapter 2 describes a new non-equilibrium framework to analyze gliding animals and how the pitch angle affects their translational motion. Chapter 3 combines flying snake glide experiments and detailed dynamic modeling to address what is aerial undulation and how each kinematic component affects rotational stability and translational performance. Chapter 4 combines the kinematic data of Chapter 3, with elements of the non-equilibrium framework of Chapter 2, to examine the kinematics of snake flight in greater detail. This chapter also tests if our current understanding of flying snake aerodynamics is sufficient to explain the observed center of mass motion. Ph. D. Flying snakes can move unlike any other flying or slithering animal. Flying snakes have evolved the ability to glide safely to the ground by undulating through the air. Flapping flyers, like birds, bats, and insects, move through the air using wings and powerful flight muscles. In contrast, gliding animals fall through the air, using gravity to increase their speed, and air resistance to produce lift and drag forces such that they move over the ground. Flying snakes glide by jumping, flattening their bodies (similar to a cobra hooding), and undulating through the air using an ‘S’-shaped body. This dissertation addresses the question, how and why do flying snakes undulate through the air? First, I describe a new mathematical analysis of gliding animals, which provides a framework to understand how an animal’s size and orientation to the oncoming airflow affect its glide performance. Second, I describe glide experiments where the bodies of flying snakes were measured as they flew through a large indoor glide arena. From these measurements, we quantified how the body bends in the horizontal and vertical directions. Next, I describe a detailed mathematical model used to test how the different body configurations we measured affect glide performance and flight stability. The model result indicate that flying snakes likely use aerial undulation to stabilize their rotational motion. Third, I tested if our current measurements of the lift and drag properties of flying snakes, based on the quasi-steady assumption, can account for the trajectories we recorded. The force analysis suggests that flying snakes produce more force than the quasi-steady assumption can account for, and that future work is needed to understand unsteady aerodynamic mechanisms relevant for snake flight. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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