title: Tonal noise of a controlled-diffusion airfoil at low angle of attack and Reynolds number.
abstract: The acoustic signature of a controlled-diffusion airfoil immersed in a flow is experimentally characterized. Acoustic measurements have been carried out in an anechoic open-jet-wind-tunnel for low Reynolds numbers (from 5 × 10(4) to 4.3 × 10(5)) and several angles of attack. As with the NACA0012, the acoustic spectrum is dominated by discrete tones. These tonal behaviors are divided into three different regimes. The first one is characterized by a dominant primary tone which is steady over time, surrounded by secondary peaks. The second consists of two unsteady primary tones associated with secondary peaks and the third consists of a hump dominated by several small peaks. A wavelet study allows one to identify an amplitude modulation of the acoustic signal mainly for the unsteady tonal regime. This amplitude modulation is equal to the frequency interval between two successive tones. Finally, a bispectral analysis explains the presence of tones at higher frequencies.
authors.affiliation: Department of Mechanical Engineering, Université de Sherbrooke, 2500 Boulevard de l'Université, Sherbrooke, Quebec J1K 2R1, Canada thomas.padois@usherbrooke.ca, paul.laffay@usherbrooke.ca, alexandre.idier@usherbrooke.ca, Stephane.Moreau@usherbrooke.ca.
authors.forename: Thomas
authors.initials: T
authors.lastname: Padois
authors.affiliation: Department of Mechanical Engineering, Université de Sherbrooke, 2500 Boulevard de l'Université, Sherbrooke, Quebec J1K 2R1, Canada thomas.padois@usherbrooke.ca, paul.laffay@usherbrooke.ca, alexandre.idier@usherbrooke.ca, Stephane.Moreau@usherbrooke.ca.
authors.forename: Paul
authors.initials: P
authors.lastname: Laffay
authors.affiliation: Department of Mechanical Engineering, Université de Sherbrooke, 2500 Boulevard de l'Université, Sherbrooke, Quebec J1K 2R1, Canada thomas.padois@usherbrooke.ca, paul.laffay@usherbrooke.ca, alexandre.idier@usherbrooke.ca, Stephane.Moreau@usherbrooke.ca.
authors.forename: Alexandre
authors.initials: A
authors.lastname: Idier
authors.affiliation: Department of Mechanical Engineering, Université de Sherbrooke, 2500 Boulevard de l'Université, Sherbrooke, Quebec J1K 2R1, Canada thomas.padois@usherbrooke.ca, paul.laffay@usherbrooke.ca, alexandre.idier@usherbrooke.ca, Stephane.Moreau@usherbrooke.ca.
authors.forename: Stéphane
authors.initials: S
authors.lastname: Moreau