Bio-Inspired Trailing Edge Noise Control: Acoustic and Flow Measurements

Trailing edge noise control is an important problem associated mainly with wind turbines. As turbulence in the air flows over a wind turbine blade, it impacts the trailing edge and scatters, producing noise. Traditional methods of noise control involve modifying the physical trailing edge, or the scattering efficiency. Recently, inspired by the downy covering of owl feathers, researchers developed treatments that can be applied to the trailing edge to significantly reduce trailing edge noise. It was hypothesized that the noise reduction was due to manipulating the incoming turbulence, rather than the physical trailing edge itself, representing a new method of noise control. However, only acoustic measurements were reported, meaning the associated flow physics were still unknown. This thesis describes a comprehensive wall jet experiment to measure the flow effects near the bio-inspired treatments, termed “finlets” and “rails,” and relate those flow effects to the noise reduction. This was done using far-field microphones, a single hot-wire probe, and surface pressure fluctuation microphones. The far-field noise results showed that each treatment successfully reduced the noise, by up to 7 dB in some cases. The surface pressure measurements showed that the spanwise coherence was slightly reduced when the treatments were applied to the trailing edge. The velocity measurements clearly established the presence of a shear layer near the top of the treatments. As a whole, the dataset led to the shear-sheltering hypothesis: the bio-inspired treatments are effective based on reducing the spanwise pressure correlation and by sheltering the trailing edge from turbulent structures with the shear layer they create.

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

2017

Author dc:creator

• Millican, Anthony J.

Chair dc:contributor.committeechair

• Devenport, William J.

Committee members dc:contributor.committeemember

• Lowe, K. Todd
• Alexander, William Nathan

• Aeroacoustics
• Trailing Edge Noise
• Noise Control
• Bio-Inspired
• Shear Sheltering
• Turbulent Wall Jet
• Hot-Wire Anemometry
• Mixing Layer

Statement dc:rights

• Creative Commons Attribution-ShareAlike 3.0 United States

Licence dc:rights.uri

• http://creativecommons.org/licenses/by-nc-sa/3.0/us/

Language dc:language.iso

en_US

Handle dc:identifier.uri

http://hdl.handle.net/10919/78376

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/78376