Abstract
dc:description.abstractThe wings of most species of owl have been shown to possess three unique physical attributes which allow them to hunt in effective silence: a comb of evenly-spaced bristles along the wing leading-edge; a compliant and porous fringe of feathers at the trailing-edge; and a velvety down material distributed over the upper wing surface. This investigation focuses on the last of the mechanisms as a means to reduce noise from flow over surface roughness. A microscopic study of several owl feathers revealed the structure of the velvety down to be very similar to that of a forest or a field of crops. Analogous surface treatments (suspended canopies) were designed which simulated the most essential geometric features of the velvety down material. The Virginia Tech Anechoic Wall-Jet Facility was used to perform far-field noise and surface pressure fluctuation measurements in the presence of various combinations of rough surfaces and suspended canopies. All canopies were demonstrated to have a strong influence on the surface pressure spectra, and attenuations of up to 30 dB were observed. In addition, all canopies were shown to have some positive effects on far-field noise, and optimized canopies yielded far-field noise reductions of up to 8 dB across all frequencies at which roughness noise was observed. This development represents a new passive method for roughness noise control with possibility for future optimization and application to engineering structures.
Degree
thesis:*- Name thesis:degree_name
- Master of Science
- Level thesis:degree_level
- masters
- Discipline thesis:degree_discipline
- Aerospace Engineering
- Department dc:contributor.department
- Aerospace and Ocean Engineering
- Grantor dc:publisher
- Virginia Tech
- Year dc:date.issued
- 2015
Author and committee
dc:creator, dc:contributor.*- Author dc:creator
-
- Clark, Ian Andrew
- Chair dc:contributor.committeechair
-
- Devenport, William J.
- Committee members dc:contributor.committeemember
-
- Alexander, William Nathan
- Paterson, Eric G.
Subjects
dc:subject × 5Rights
dc:rights- Statement dc:rights
-
- In Copyright
- Licence dc:rights.uri
Identifiers
dc:identifier.*- Dc Identifier Other
- vt_gsexam:4367
- OAI identifier oai:identifier
- oai:vtechworks.lib.vt.edu:10919/51178