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Aeroacoustic sound generation in simple expansion chambers
Emmet J English1, Keith R Holland
1Institute of Sound and Vibration Research, University of Southampton, Southampton S017 1BJ, United Kingdom.
The Journal of the Acoustical Society of America
|November 30, 2010
Summary
This study introduces a novel method for measuring aeroacoustic source strength in ducts using coherent power flux. The findings reveal the generation of flow tones in expansion chambers, offering insights into duct acoustics.
Area of Science:
- Acoustics
- Fluid Dynamics
- Vibrations
Background:
- Measuring aeroacoustic source strength in ducts is crucial for understanding noise generation in systems with airflow.
- Existing methods may have limitations at specific frequencies or flow conditions.
- One-dimensional wave motion assumptions simplify analysis but require validation.
Purpose of the Study:
- To present a new method for measuring aeroacoustic source strength in ducts under one-dimensional flow conditions.
- To apply this method to an expansion chamber and analyze flow-excited tones.
- To compare experimental results with theoretical predictions.
Main Methods:
- Utilized coherent power flux measurements with upstream and downstream microphone pairs.
- Investigated an expansion chamber with varying flow velocities and lengths.
- Employed describing function theory for resonator analysis with grazing flow.
Main Results:
- Successfully measured aeroacoustic source strength in the duct system.
- Observed the generation of locked-on flow tones within the expansion chamber.
- Quantified the frequency of these flow tones across different experimental conditions.
Conclusions:
- The presented method is effective for measuring aeroacoustic source strength in ducts.
- Locked-on flow tones are a significant phenomenon in flow-excited expansion chambers.
- Experimental frequencies of flow tones show agreement with theoretical predictions, validating the approach.
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