Investigations of Partially Immersed Spinning Spheres in a Liquid Bath and Butterfly Flight
This thesis examines two important problems in fluid dynamics: that of a partially immersed sphere spinning in a bath of liquid and the measurement of flow velocities around a free flying butterfly. Although the actual problems are quite different, each problem incorporates many of the same principl...
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| Format: | Others |
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BYU ScholarsArchive
2013
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| Online Access: | https://scholarsarchive.byu.edu/etd/3948 https://scholarsarchive.byu.edu/cgi/viewcontent.cgi?article=4947&context=etd |
| Summary: | This thesis examines two important problems in fluid dynamics: that of a partially immersed sphere spinning in a bath of liquid and the measurement of flow velocities around a free flying butterfly. Although the actual problems are quite different, each problem incorporates many of the same principles and techniques. When a hard-boiled egg spins through a pool of milk on the kitchen counter, the milk rises up the sides of the egg and droplets are ejected. This phenomenon occurs when any partially submerged object whose radius increases upward from the fluid surface (e.g., spheres, inverted cones, rings, etc.), spins in a shallow bath of fluid. The fluid ejects from the surface at the maximum diameter in one of three ejection modes: jets, sheets, or sheet breakup. Additionally, a surprisingly large flow rate is induced by the spinning object. Spheres are used in this study to determine the effects of experimental parameters on the induced flow rate. High-speed imaging is used to experimentally characterize the modes of ejection and measure sheet breakup distance and velocities of liquid within liquid sheets. A theoretical model is derived using an integral momentum boundary layer analysis both beneath the free surface and in the thin film attached to the sphere. Experimental results are presented in comparison with predicted behavior with good agreement. The suitability of using a spinning sphere as a pump is also discussed. Second, the use of PIV to measure flow velocities around living species is becoming more widely adopted. Current efforts are starting to measure 3D, time-resolved velocities around insects in tethered flight. This work investigates the use of Synthetic Aperture PIV (SAPIV) in obtaining 3D, time-resolved volumetric velocity fields around a painted lady butterfly in free flight. Results are presented from several time steps during both the down stroke and upstroke of the butterfly showing the development of the leading edge vortex. The velocity field results have limited spatial resolution; however, the results show that SAPIV has potential in further investigating these flow structures. The reconstructed visual hull of the butterfly is also discussed. |
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