Title:
Separating Contributions of Small-Scale Turbulence, Large-Scale Turbulence, and Core Noise from Far-Field Exhaust Noise Measurements

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dc.contributor.advisor Ahuja, Krishan K.
dc.contributor.author Nance, Donald Kirby en_US
dc.contributor.committeeMember Cunefare, Kenneth A.
dc.contributor.committeeMember Lieuwen, Timothy C.
dc.contributor.committeeMember Mendoza, Jeff
dc.contributor.committeeMember Sankar, Lakshmi N.
dc.contributor.department Aerospace Engineering en_US
dc.date.accessioned 2008-02-07T18:17:52Z
dc.date.available 2008-02-07T18:17:52Z
dc.date.issued 2007-08-24 en_US
dc.description.abstract The two-noise source model for predicting jet noise claims that the radiated jet noise is composed of two distinct sources one associated with the small-scale turbulence and another associated with the large-scale turbulence. The former source is claimed to radiate noise predominantly at larger angles with respect to the downstream jet axis, whereas the large-scale turbulence radiates predominantly at the shallower angles. A key objective of this effort is to experimentally validate this model using correlation and coherence measurements. Upon the successful validation of the two-noise source model for jets exhausting from multiple nozzle geometries driven at Mach numbers ranging from subsonic to supersonic, a three-microphone signal enhancement technique is employed to separate the contribution of the small-scale turbulence from that of the large-scale turbulence in the far-field. This is the first-ever quantitative separation of the contributions of the turbulence scales in far-field jet noise measurements. Furthermore, by suitable selection of far-field microphone positions, the separation of the contribution of any internal or core noise from that of the jet-mixing noise is achieved. Using coherence-based techniques to separate the contributions of the small-scale turbulence, large-scale turbulence, and any internal or core noise from far-field exhaust noise measurements forms the backbone of this effort. In the application of coherence-based multiple-microphone signal processing techniques to separate the contributions of the small-scale turbulence, large-scale turbulence, and any internal or core noise in the far-field, research efforts focus on three techniques (1) the coherent output power spectrum using two microphones, (2) an ordinary coherence method using the three-microphone technique, and (3) the partial-coherence method using five microphones. The assumption of jet noise incoherence between correlating microphone is included in each of these methods. In light of the noise radiation mechanisms described within the framework of the two-noise source model and their spatial characteristics as experimentally determined in the far-field, the assumption of jet noise incoherence is evaluated through a series of experiments designed to study jet noise coherence across a variety of nozzle geometries and jet Mach numbers ranging from subsonic to supersonic. Guidelines for the suitable selection of far-field microphone locations are established. en_US
dc.description.degree Ph.D. en_US
dc.identifier.uri http://hdl.handle.net/1853/19768
dc.publisher Georgia Institute of Technology en_US
dc.subject Core noise en_US
dc.subject Two-noise source model en_US
dc.subject Correlation en_US
dc.subject Turbulence en_US
dc.subject Coherence en_US
dc.subject Three-microphone method en_US
dc.subject Jet noise incoherence en_US
dc.subject.lcsh Jet planes
dc.subject.lcsh Aerodynamic noise
dc.title Separating Contributions of Small-Scale Turbulence, Large-Scale Turbulence, and Core Noise from Far-Field Exhaust Noise Measurements en_US
dc.type Text
dc.type.genre Dissertation
dspace.entity.type Publication
local.contributor.advisor Ahuja, Krishan K.
local.contributor.corporatename College of Engineering
local.contributor.corporatename Daniel Guggenheim School of Aerospace Engineering
local.relation.ispartofseries Doctor of Philosophy with a Major in Aerospace Engineering
relation.isAdvisorOfPublication 22e5838d-630c-400b-bee3-4ddf9759b86d
relation.isOrgUnitOfPublication 7c022d60-21d5-497c-b552-95e489a06569
relation.isOrgUnitOfPublication a348b767-ea7e-4789-af1f-1f1d5925fb65
relation.isSeriesOfPublication f6a932db-1cde-43b5-bcab-bf573da55ed6
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