Effect of external acoustic excitation on NACA0015 discrete tonal noise
The purpose of this work is to investigate the effect of external acoustic excitation on the discrete tonal noise generated by laminar boundary layer instability. Experimental testing inside anechoic wind tunnel was done on NACA0015 in order to measure the sound spectrum at low Reynolds number of...
| Main Authors: | , |
|---|---|
| Format: | Article |
| Language: | English English |
| Published: |
Elsevier Ltd.
2018
|
| Subjects: | |
| Online Access: | http://irep.iium.edu.my/69945/ http://irep.iium.edu.my/69945/ http://irep.iium.edu.my/69945/1/%5B2018%5DEffect%20of%20external%20acoustic%20excitation%20on%20NACA0015%20discrete%20tonal%20noise.pdf http://irep.iium.edu.my/69945/7/69945_Effect%20of%20external%20acoustic%20excitation_SCOPUS.pdf |
| Summary: | The purpose of this work is to investigate the effect of external acoustic excitation on the discrete tonal noise
generated by laminar boundary layer instability. Experimental testing inside anechoic wind tunnel was done on
NACA0015 in order to measure the sound spectrum at low Reynolds number of Re∼104 and angle of attack of 0°,
3° and 5°. The effects of excitation amplitude of 70 dB and 90 dB and excitation frequency of 3000 Hz and
2000 Hz on the airfoil discrete tones were investigated. Exciting at excitation frequency closed to the primary
frequency was found able to suppress tonal noise, however, is highly dependent on the angle of attack and
freestream velocity. The airfoil was found to have a strong preference in its tonal frequency regardless of excitation.
No change was found on the dependency of the secondary frequency. Each individual frequency was
found to have ∼U0.8 dependency with freestream velocity that is similar to that without excitation. In general,
observation shows acoustic excitation only affect the behavior of the primary frequency. The primary frequency
dependency at α =0° was found changed to∼U2.0 with acoustic excitation at 3000 Hz and 90 dB and at 2000 Hz
and 70 dB. |
|---|