This dissertation aims to contribute toward the understanding of water-entry and -exit behaviors in nature. Since water is nearly a thousand times denser than air, transitioning between the two mediums is often associated with significant changes in force. Three topics with implications in water-entry are discussed, along with a fourth topic on water-exit. For a plunge-diving seabird, the first two stages of water-entry (initial impact and air-cavity formation) create large stresses on the bird's neck. Linear stability analysis of a cone-beam system impacting water shows buckling and non-buckling behaviors on the beam, which is extended to the diving birds. The next topic is related to the third stage of water-entry (air-cavity pinch-off), in which the chest feathers come in contact with the water. Here, the elasticity of Northern Gannet contour feathers is calculated using the nonlinear bending equation. The third topic will explore the formation of ripples along air cavity walls and their resulting force after pinch-off. An acoustic model predicts the observed wavelengths of the ripples. The final topic will delve into the mechanics of how animals leap out of water. A scaling law that balances the power of thrust and drag will predict the height of the jump. Finally, a bio-inspired robot was built to help identify physical conditions required to jump out of water. / Ph. D. / In nature, animals use enter and exit water (water-entry and water-exit, respectively) as a strategy for hunting prey and/or escaping predators. In this dissertation, we focus on the fluid mechanics of water-entry and water-exit phenomena as it pertains to animals. First, we study how seabirds plunge-dive into water at high speeds without neck injuries. Second, we discuss calculating the elasticity of bird feathers. Next, the rippling behavior of air-cavities is studied in the context of force production. Finally, we study the water-exit phenomenon of animals leaping out of water. The topics of this dissertation have implications in the water-entry and -exit of vehicles and autonomous robotics.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/83445 |
| Date | 01 June 2018 |
| Creators | Chang, Brian Lida |
| Contributors | Engineering Science and Mechanics, Jung, Sunghwan, Socha, John J., Abaid, Nicole, Ragab, Saad A., Barone, Justin R. |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Detected Language | English |
| Type | Dissertation |
| Format | ETD, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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