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A Study of Bio-Inspired Canopies for the Reduction of Roughness Noise

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dc.contributor.authorClark, Ian Andrewen
dc.contributor.committeechairDevenport, William J.en
dc.contributor.committeememberAlexander, William Nathanen
dc.contributor.committeememberPaterson, Eric G.en
dc.contributor.departmentAerospace and Ocean Engineeringen
dc.date.accessioned2015-01-10T09:00:23Zen
dc.date.available2015-01-10T09:00:23Zen
dc.date.issued2015-01-09en
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.en
dc.description.degreeMaster of Scienceen
dc.format.mediumETDen
dc.identifier.othervt_gsexam:4367en
dc.identifier.urihttp://hdl.handle.net/10919/51178en
dc.publisherVirginia Techen
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subjectRoughness Noiseen
dc.subjectBio-Inspireden
dc.subjectNoise Reductionen
dc.subjectNoise Controlen
dc.subjectCanopiesen
dc.titleA Study of Bio-Inspired Canopies for the Reduction of Roughness Noiseen
dc.typeThesisen
thesis.degree.disciplineAerospace Engineeringen
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen
thesis.degree.levelmastersen
thesis.degree.nameMaster of Scienceen

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