Effect of external acoustic excitation on NACA0015 discrete tonal noise

Andan, Amelda Dianne and Lee, Duck-Joo (2018) Effect of external acoustic excitation on NACA0015 discrete tonal noise. Applied Acoustics, 141. pp. 374-381. E-ISSN 0003-682X

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Abstract

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.

Item Type:	Article (Journal)
Additional Information:	8376/69945
Uncontrolled Keywords:	Airfoil discrete tonal noise, External acoustic excitation, Laminar boundary layer instability
Subjects:	T Technology > TL Motor vehicles. Aeronautics. Astronautics > TL500 Aeronautics
Kulliyyahs/Centres/Divisions/Institutes (Can select more than one option. Press CONTROL button):	Kulliyyah of Engineering > Department of Mechanical Engineering Kulliyyah of Engineering
Depositing User:	Dr. Amelda Dianne Andan
Date Deposited:	28 Jan 2019 10:58
Last Modified:	28 Jan 2019 10:58
URI:	http://irep.iium.edu.my/id/eprint/69945

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