In the field of supersonic jet noise, measurements of full-scale afterburning jet engines are infrequent and provide unique opportunities to better understand jet noise phenomena. This thesis represents a phenomenological jet noise analysis using far-field noise data collected from a T-7A-installed GE F404-103 turbofan engine. One issue with the far-field acoustic data from the T-7A was the effects of ground reflections present in the spectra generated from the measured waveforms. A previously developed ground reflection model was implemented into the data to account for this interference. This work represents the first time this model has been implemented in data collected from a full-scale aircraft. Spectra and spatiospectral maps are used to show that, while imperfect, this model represents a step in the right direction for accounting for ground reflections. From the ground reflection-corrected data, sound power values were calculated at varying engine powers. These values were compared against mechanical power values calculated using provided engine parameters at the corresponding engine conditions. It is shown that the observed increase in sound power with mechanical power at supersonic engine conditions follows classical jet noise theory, while the increase between transonic engine conditions is much greater than predicted by classical jet noise theory. This divergence is currently unexplained. Finally, far-field noise directivity measured from the T-7A is connected back to both physics-based and empirically derived definitions of the convective Mach number, a dimensionless parameter used to describe the velocities of coherent structures in the turbulent mixing layer of a jet. For supersonic jets, where Mach wave radiation is the dominant noise source, the convective Mach number should be useful for predicting peak directivity angles. The evaluated definitions show that the convective Mach number associated with Kelvin-Helmholtz instability waves best predicts the peak directivity of the T-7A.
| Identifer | oai:union.ndltd.org:BGMYU2/oai:scholarsarchive.byu.edu:etd-11185 |
| Date | 21 November 2023 |
| Creators | Christian, Matthew Austin |
| Publisher | BYU ScholarsArchive |
| Source Sets | Brigham Young University |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | Theses and Dissertations |
| Rights | https://lib.byu.edu/about/copyright/ |
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