Show simple item record

dc.contributor.authorNance, Donald Kirbyen_US
dc.date.accessioned2008-02-07T18:17:52Z
dc.date.available2008-02-07T18:17:52Z
dc.date.issued2007-08-24en_US
dc.identifier.urihttp://hdl.handle.net/1853/19768
dc.description.abstractThe 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.publisherGeorgia Institute of Technologyen_US
dc.subjectCore noiseen_US
dc.subjectTwo-noise source modelen_US
dc.subjectCorrelationen_US
dc.subjectTurbulenceen_US
dc.subjectCoherenceen_US
dc.subjectThree-microphone methoden_US
dc.subjectJet noise incoherenceen_US
dc.subject.lcshJet planes
dc.subject.lcshAerodynamic noise
dc.titleSeparating Contributions of Small-Scale Turbulence, Large-Scale Turbulence, and Core Noise from Far-Field Exhaust Noise Measurementsen_US
dc.typeDissertationen_US
dc.description.degreePh.D.en_US
dc.contributor.departmentAerospace Engineeringen_US
dc.description.advisorCommittee Chair: Ahuja, Krishan K.; Committee Member: Cunefare, Kenneth; Committee Member: Lieuwen, Tim C.; Committee Member: Mendoza, Jeff; Committee Member: Sankar, Lakshmien_US


Files in this item

Thumbnail

This item appears in the following Collection(s)

Show simple item record