Description
- Abstract:
- We present a study of the aeromechanics of highly compliant structures in the context of animal flight, with special attention paid to bat flight. Bats are unique among animal flyers because of their highly articulated wings that are composed of a thin skin membrane and a skeletal structure that contains many long and slender bones. Therefore, signicant shape change occurs throughout the wingbeat cycle as a consequence of a strong coupling between the aerodynamic forces and the wing structure. Using high speed videography and photogrammetry techniques, the in-flight shape, motion and articulation of the wing were measured for wind tunnel flights of several individuals of Cynopterus brachyotis for wind speeds ranging from U = 2.6 - 6.6 m/s. The inboard portion of the wing membrane exhibited large, anisotropic strains with the membrane area increasing to nearly three times the minimum area for the wingbeat cycle, but with little to no flight speed dependence. In addition, the leading edge was found to nearly align with the oncoming flow for flight conditions tested perhaps limiting or controlling flow separation that would lead to the formation of a leading edge vortex (LEV). The aeromechanics of the bat wing is distilled into a system consisting of two components: 1) a compliant membrane and 2) an elastic structure with a resonant frequency near the natural vortex shedding frequency. The steady aerodynamic and unsteady aeromechanical behavior of a latex membrane wing were measured in a series of wind tunnels tests, which showed the enhanced lift behavior due the adaptive cambering of these elastic membrane wings. We modulate the strength and stability of the flat plate leading edge vortex using only one degree of freedom (pitching) in both passive and forced plate motion. We measure the resultant aerodynamic moment as an indicator of the vortex strength and near-plate residence time. We conclude with a description and implementation of a cyberphysical flat plate that is mounted to a virtual spring-damper system that enables software control of the torsion spring stiffness and damping.
- Notes:
- Thesis (Ph.D. -- Brown University (2013)
Access Conditions
- Rights
- In Copyright
- Restrictions on Use
- Collection is open for research.
Citation
Song, Arnold J.,
"Aeromechanics of highly compliant structures: Bat wings, compliant membranes and flexibly mounted flat plates"
(2013).
Fluid, Thermal, and Chemical Processes Theses and Dissertations.
Brown Digital Repository. Brown University Library.
https://doi.org/10.7301/Z0BC3WWH
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Fluid, Thermal, and Chemical Processes Theses and Dissertations
Theses and Dissertations for the Fluid, Thermal, and Chemical Processes department....