Towards quieter supersonic flight : a computational aeroacoustic study of high-speed jets
Abstract/Contents
- Abstract
- Using large-eddy simulations (LES) and the Ffowcs Williams-Hawkings (FW-H) method, this thesis studies aeroacoustic phenomena in high-speed jet flows from supersonic aircraft engines. The work is divided to two parts. The first part focuses on jet screech in an underexpanded rectangular jet plume—a challenging aeroacoustic resonance emitting disruptive tonal noise. A detailed numerical study identifies optimal mesh designs and FW-H sampling, yielding accurate screech results with moderate computational and storage costs. This investigation reveals that screech involves energy transfer between the upstream-traveling guided jet mode and the downstream-traveling Kelvin-Helmholtz wave. Distinct regions in the spatially developing jet can be identified based on the wave energy of oppositely-moving waves. The near-nozzle region is found to be related to the receptivity of the initial shear layers, followed by a region further downstream where the wave energies reach maximal values. The SPOD modes can be used to reconstruct the amplitude and directivity of the fundamental screech tone with Lighthill's acoustic analogy. The second part of the thesis centers on dual-stream coaxial nozzles with internal mixing geometries for noise reduction in supersonic business aircraft. Analysis of nearfield flow turbulence highlights internal shear layers and wakes introduced by the mixing geometry, impacting the near-nozzle external jet flow even in absence of the temperature and velocity differences between the two streams. Two coaxial nozzles with an internal center plug and a mixing duct are studied: one with a 16-lobe mixer and one without. A comparison of the coaxial jet with its fully mixed equivalent single jet condition shows that the coaxial jet is louder in the downstream direction. The equivalent single jet emits acoustic tones in the upstream direction, likely due to the excitation of instability waves in the shear layers. Overall, this study improves the understanding of screech generation and coaxial jet aeroacoustics, offering insights for quieter supersonic aircraft design in the future.
Description
| Type of resource | text |
|---|---|
| Form | electronic resource; remote; computer; online resource |
| Extent | 1 online resource. |
| Place | California |
| Place | [Stanford, California] |
| Publisher | [Stanford University] |
| Copyright date | 2023; ©2023 |
| Publication date | 2023; 2023 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Author | Wu, Gao Jun |
|---|---|
| Degree supervisor | Lele, Sanjiva K. (Sanjiva Keshava), 1958- |
| Thesis advisor | Lele, Sanjiva K. (Sanjiva Keshava), 1958- |
| Thesis advisor | Alonso, Juan José, 1968- |
| Thesis advisor | Bres, Guillaume |
| Thesis advisor | Moin, Parviz |
| Degree committee member | Alonso, Juan José, 1968- |
| Degree committee member | Bres, Guillaume |
| Degree committee member | Moin, Parviz |
| Associated with | Stanford University, School of Engineering |
| Associated with | Stanford University, Department of Aeronautics and Astronautics |
Subjects
| Genre | Theses |
|---|---|
| Genre | Text |
Bibliographic information
| Statement of responsibility | Gao Jun (Gary) Wu. |
|---|---|
| Note | Submitted to the Department of Aeronautics and Astronautics. |
| Thesis | Thesis Ph.D. Stanford University 2023. |
| Location | https://purl.stanford.edu/ty736kn1173 |
Access conditions
- Copyright
- © 2023 by Gao Jun Wu
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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