Tonal generation by an airfoil at low to moderate Reynolds numbers

Gijsman, F. (2014) Tonal generation by an airfoil at low to moderate Reynolds numbers.

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Abstract:This test report describes tonal noise generation by an airfoil at low to moderate Reynolds numbers. Acoustic and PIV measurements were carried out on a NACA0012 profile in NLR’s Small Anechoic Wind Tunnel KAT. The main objective was to provide insight into the aeroacoustic source mechanism using PIV measurements. Airfoil tonal noise and flow properties around a NACA0012 profile with a moderately blunt trailing edge for different wind speeds and angles of attack were determined. In order to isolate airfoil tonal noise sources, acoustic measurements were done using a 48-microphone phased array. PIV measurements were performed in a frame of 24 mm by 24 mm around the trailing edge to analyse the flow phenomena in the source region. The measurements were carried out for the velocity range of 15 m/s to 35 m/s, representing Reynolds numbers of 1 ⋅ 105 to 2.5 ⋅ 105. Laminar boundary layer vortex shedding and trailing edge bluntness vortex shedding were observed and investigated. Intense narrow band tones were found that could be related to both laminar boundary layer- and trailing edge bluntness vortex shedding noise. From 15 m/s till 27.5 m/s the phenomena worked separately, at higher speeds they start to interact. A linear scaling of the peak frequencies with the velocity is found. All deviations of this pattern can be explained by different flow patterns, shown by the PIV measurements
Item Type:Internship Report (Master)
Clients:
NLR, the Netherlands
Faculty:ET: Engineering Technology
Subject:52 mechanical engineering
Programme:Mechanical Engineering MSc (60439)
Keywords:Noise propagation, PIV, Acoustic measurements, airfoils
Link to this item:http://purl.utwente.nl/essays/69268
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