Virginia Tech
Rotor Inflow Noise Caused by a Boundary Layer: Inflow Measurements and Noise Predictions
Abstract
dc:description.abstractA rotor immersed in a thick turbulent boundary layer produces unsteady loading on the blades which generates unwanted noise and vibration. Two point velocity fluctuations were measured in detail to determine the full four-dimensional correlation function of a boundary layer generated over a smooth wall in the Virginia Tech Stability Wind Tunnel. The correlation function reveals anisotropy in the flow dominated by a large scale correlation structure elongated in the streamwise direction and inclined relative to the wall. This correlation function was then evaluated in the blade frame of reference of an idealized 10 bladed rotor partially immersed in the flow. Blade to blade upwash coherence shows significant asymmetry which is a direct result of the anisotropy of the flow. Using a newly developed theory, the correlation function was used to predict the far-field radiated noise from the rotor at various operating and flow conditions. Predictions show the sound field is dominated by the effects of "haystacking" which is further increased with the inclusion of the presence of the wall. Directivity predictions suggest the far-field sound field acts like a monopole/dipole combination.
Degree
thesis:*- Name thesis:degree_name
- Master of Science
- Level thesis:degree_level
- masters
- Discipline thesis:degree_discipline
- Aerospace and Ocean Engineering
- Department dc:contributor.department
- Aerospace and Ocean Engineering
- Grantor dc:publisher
- Virginia Tech
- Year dc:date.issued
- 2012
Author and committee
dc:creator, dc:contributor.*- Author dc:creator
-
- Morton, Michael Andrew
- Chair dc:contributor.committeechair
-
- Devenport, William J.
- Committee members dc:contributor.committeemember
-
- Lowe, K. Todd
- Glegg, Stewart A. L.
Subjects
dc:subject × 5Rights
dc:rights- Statement dc:rights
-
- In Copyright
- Licence dc:rights.uri
Identifiers
dc:identifier.*- Dc Identifier Other
- etd-08102012-103032
- OAI identifier oai:identifier
- oai:vtechworks.lib.vt.edu:10919/34467