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Transitional wall pressure fluctuations on axisymmetric bodies
Chinsuk Hong1, Ku-Kyun Shin, Jae-Jin Jeon
1Agency for Defense Development, P.O. Box 18, Chinhae, Kyungnam 645-600, Republic of Korea. cshong@pusan.ac.kr
The Journal of the Acoustical Society of America
|December 3, 2008
Summary
This study details wall pressure fluctuations in transitional boundary layers over axisymmetric bodies. Tollmien-Schlichting waves intensify downstream, with their characteristic frequency related to outer variables, showing higher peak levels than fully developed flows.
Area of Science:
- Fluid dynamics
- Aerodynamics
- Acoustics
Background:
- Understanding transitional boundary layers is crucial for predicting aerodynamic noise and performance.
- Wall pressure fluctuations are key indicators of flow instabilities like Tollmien-Schlichting waves.
Purpose of the Study:
- To characterize wall pressure fluctuations in the transitional flow regime over axisymmetric bodies.
- To investigate the spatial and temporal development of Tollmien-Schlichting waves.
- To establish relationships between flow parameters and pressure fluctuation characteristics.
Main Methods:
- Measurements in a low-noise wind tunnel using hot wires, micromanometers, and flush-mounted microphones.
- Time-domain analysis for spatial and temporal development of Tollmien-Schlichting (T-S) waves.
- Wigner-Ville distributions for joint time-frequency energy evolution analysis.
Main Results:
- Transitional wall pressure fluctuations appear as intermittent pulses, intensifying downstream at approximately 63% of upstream velocity.
- T-S wave center frequency decreases with increasing boundary-layer thickness.
- Energy distribution bandwidth broadens with increasing local Reynolds number.
- A characteristic T-S wave frequency relation: omegadelta(*)/U(infinity) ≈ 0.2.
- Peak pressure fluctuation levels in late transition are ~10 dB higher than in fully developed flow.
Conclusions:
- The study provides detailed insights into the nature and scaling of wall pressure fluctuations during flow transition.
- Findings contribute to improved modeling of aerodynamic noise and transition prediction in external flows.
- The identified characteristic frequency offers a valuable parameter for transition analysis.
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