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dc.contributor.advisorKerschen, Eden_US
dc.contributor.authorMYERS, MATTHEW RONALD.
dc.creatorMYERS, MATTHEW RONALD.en_US
dc.date.accessioned2011-10-31T16:56:54Z
dc.date.available2011-10-31T16:56:54Z
dc.date.issued1987en_US
dc.identifier.urihttp://hdl.handle.net/10150/184032
dc.description.abstractThis dissertation investigates the effect of airfoil steady loading on the sound generated by the interaction of an isolated, zero-thickness airfoil with a high-frequency convected disturbance. The analysis is based on a linearization of the inviscid equations of motion about a nonuniform mean flow. The mean flow is assumed to be two-dimensional and subsonic. Throughout most of the dissertation, we assume that the Mach number is 0(1), though in one section we concentrate on the leading-edge region and study the behavior of the sound field as the Mach number tends to zero. The small parameter representing the amount of airfoil camber and incidence angle, and the large parameter representing the ratio of airfoil chord to disturbance wavelength, are utilized in a singular perturbation analysis. The analysis shows that essentially all of the sound is generated at the leading and trailing edges, in regions the size of the disturbance wavelength. The solution in the local-leading-edge region reveals several sound-generating mechanisms which do not exist for an airfoil with no mean loading. These mechanisms are not present at the trailing edge; the trailing edge is important only as a scatterer of the sound produced at the leading edge. The propagation of sound away from the airfoil edges is described by geometric acoustics, with the amplitude varying on the scale of the airfoil chord and the phase varying on the much smaller scale of the disturbance wavelength. In addition, a diffraction-type transition region exists downstream of the airfoil. Calculations of radiated acoustic power show that the sound field depends strongly on Mach number, gust characteristics, and airfoil steady loading. Small changes in these properties can produce large changes in radiated power levels. Most importantly, we find that the amount of power radiated correlates very well with the strength of the mean flow around the leading edge.
dc.language.isoenen_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.subjectAerofoils.en_US
dc.subjectGust loads.en_US
dc.subjectAtmospheric turbulence.en_US
dc.titleEFFECT OF AIRFOIL MEAN LOADING ON HIGH-FREQUENCY GUST INTERACTION NOISE (AEROACOUSTICS, FAN, TURBOMACHINERY).en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.identifier.oclc698378558en_US
thesis.degree.grantorUniversity of Arizonaen_US
thesis.degree.leveldoctoralen_US
dc.contributor.committeememberBulsa, Thomasen_US
dc.identifier.proquest8711642en_US
thesis.degree.disciplineApplied Mathematicsen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.namePh.D.en_US
refterms.dateFOA2018-08-22T14:46:46Z
html.description.abstractThis dissertation investigates the effect of airfoil steady loading on the sound generated by the interaction of an isolated, zero-thickness airfoil with a high-frequency convected disturbance. The analysis is based on a linearization of the inviscid equations of motion about a nonuniform mean flow. The mean flow is assumed to be two-dimensional and subsonic. Throughout most of the dissertation, we assume that the Mach number is 0(1), though in one section we concentrate on the leading-edge region and study the behavior of the sound field as the Mach number tends to zero. The small parameter representing the amount of airfoil camber and incidence angle, and the large parameter representing the ratio of airfoil chord to disturbance wavelength, are utilized in a singular perturbation analysis. The analysis shows that essentially all of the sound is generated at the leading and trailing edges, in regions the size of the disturbance wavelength. The solution in the local-leading-edge region reveals several sound-generating mechanisms which do not exist for an airfoil with no mean loading. These mechanisms are not present at the trailing edge; the trailing edge is important only as a scatterer of the sound produced at the leading edge. The propagation of sound away from the airfoil edges is described by geometric acoustics, with the amplitude varying on the scale of the airfoil chord and the phase varying on the much smaller scale of the disturbance wavelength. In addition, a diffraction-type transition region exists downstream of the airfoil. Calculations of radiated acoustic power show that the sound field depends strongly on Mach number, gust characteristics, and airfoil steady loading. Small changes in these properties can produce large changes in radiated power levels. Most importantly, we find that the amount of power radiated correlates very well with the strength of the mean flow around the leading edge.


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