Aeroacoustics of turbulent mixing layers
Abstract/Contents
- Abstract
- Jet noise is an important contributor to overall aircraft noise. The flow near the jet nozzle is a spatially developing mixing layer and influences flow dynamics further downstream. The present study focuses on the influence of inflow conditions on mixing layer development and noise generation mechanisms using large-eddy simulations. Large-eddy simulations of spatially developing, turbulent mixing layers with splitter plate included in the computational domain are presented. Different inflow condition cases with initially laminar boundary layers (abbreviated as LBL) and turbulent boundary layers (abbreviated as TBL) are considered. Effect of heating, keeping the velocity ratio fixed, is analyzed for both. For each case, the mean and turbulent intensity profiles collapse when plotted in similarity coordinates. The development distance to achieve self-similarity in the mean velocity profile is found to be shortest for cases with turbulent exit boundary layers. The growth rate of the shear layer and peak self-similar values of the turbulent intensities are found to be in agreement with available experiments. It is observed that with heating, the initial instability is accelerated but the saturation self-similar amplitude of Reynolds stress components do not vary. The saturation amplitudes of density fluctuations were found to increase proportionally to difference in free-stream densities whereas near-field pressure fluctuations were found to decrease with heating. A simple scaling is suggested for the near-field pressure fluctuation amplitude. The observed scaling laws were also confirmed by simulation data from two-dimensional direct numerical simulations. For LBL, sound radiation is observed in downstream direction peaked roughly at 30 degrees. The vortex pairing and breakdown to turbulence contribute significantly to the radiated sound. For TBL, the acoustic field near the shear layer is significantly weaker and noise due to passage of boundary layer eddies over the trailing edge is observed. For both the cases, a reduction in overall sound pressure levels in the far-field is observed with heating. Analysis of relative importance of Reynolds stress autocorrelation tensor components is presented to explain the effects of heating.
Description
| Type of resource | text |
|---|---|
| Form | electronic; electronic resource; remote |
| Extent | 1 online resource. |
| Publication date | 2011 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Associated with | Sharma, Arjun |
|---|---|
| Associated with | Stanford University, Department of Mechanical Engineering |
| Primary advisor | Lele, Sanjiva K. (Sanjiva Keshava), 1958- |
| Thesis advisor | Lele, Sanjiva K. (Sanjiva Keshava), 1958- |
| Thesis advisor | Cantwell, Brian |
| Thesis advisor | Moin, Parviz |
| Advisor | Cantwell, Brian |
| Advisor | Moin, Parviz |
Subjects
| Genre | Theses |
|---|
Bibliographic information
| Statement of responsibility | Arjun Sharma. |
|---|---|
| Note | Submitted to the Department of Mechanical Engineering. |
| Thesis | Ph. D. Stanford University 2011 |
| Location | electronic resource |
Access conditions
- Copyright
- © 2011 by Arjun Sharma
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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