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TECHNICAL PAPERS

Wind Tunnel Aeroacoustic Tests of Six Airfoils for Use on Small Wind Turbines*

[+] Author and Article Information
Paul Migliore

National Renewable Energy Laboratory, National Wind Technology Center, 1617 Cole Boulevard, Golden, Colorado 80401e-mail: paul_migliore@nrel.gov

Stefan Oerlemans

National Aerospace Laboratory NLR, Department of Aeroacoustics, P.O. Box 153, 8300 AD Emmeloord, The Netherlandse-mail: stefan@nlr.nl

J. Sol. Energy Eng 126(4), 974-985 (Nov 18, 2004) (12 pages) doi:10.1115/1.1790535 History: Received January 26, 2004; Revised June 15, 2004; Online November 18, 2004
Copyright © 2004 by ASME
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References

Selig, M., and McGranahan, B., 2004, Wind Tunnel Aerodynamic Tests of Six Airfoils for Use on Small Wind Turbines, NREL SR-500-34515.
Oerlemans, S., 2004, Wind Tunnel Aeroacoustic Tests of Six Airfoils for Use on Small Wind Turbines, NREL SR-500-35339.
Moriarty, P., and Migliore, P., 2003, Semi-empirical Aeroacoustic Noise Prediction Code for Wind Turbines, NREL TP-500-34478.
Wagner, S., Bareiß, R., and Guidati, G., 1996, Wind Turbine Noise, Springer-Verlag, Berlin, pp. 14–21.
Hagg, F., Dassen, A., Parchen, R., and Bruggeman, J., 1996, Influence of the Airfoil Shape and Thickness on the Emission of Turbulence Inflow Noise as Measured in the Wind Tunnel, 1996 European Wind Energy Conference, Göteborg, Sweden.
Guidati, G., Bareiß, R., Wagner, S., Dassen, T., and Parchen, R., 1997, Simulation and Measurement of Inflow-Turbulence Noise on Airfoils, AIAA-97-1698-CP.
Brooks, T., Pope, D., and Marcolini, M., 1989, Airfoil Self-Noise and Prediction, NASA Reference Publication 1218.
Brooks, T., and Hutcheson, F., 2004, Effects of Angle of Attack and Velocity on Trailing-edge Noise, AIAA-2004-1031.
Moreau,  S., Henner,  M., Iaccarino,  G., Wang,  M., and Roger,  M., 2003, Analysis of Flow Conditions in Free Jet Experiments for Studying Airfoil Self-Noise, AIAA J., 41(10).
Amiet,  R., 1978, “Refraction of Sound by a Shear Layer,” J. Sound Vib., 58(2), pp. 467–482.
Oerlemans, S., and Sijtsma, P., 2002, Determination of Absolute Levels from Phased Array Measurements Using Spatial Source Coherence, AIAA-2002-2464.
Oerlemans, S., and Migliore, P., 2004, Aeroacoustic Wind Tunnel Tests of Wind Turbine Airfoils, AIAA-2004-3042.
Pott-Pollenske, M., Dobrzynski, W., Buchholz, H., Gehlar, B., and Walle, F., 2002, Validation of a Semi empirical Airframe Noise Prediction Method through Dedicated A319 Flyover Noise Measurements, AIAA 2002-2470.
Pott-Pollenske, M., Alvarez-Gonzalez, J., and Dobrzynski, W., Effect of Slat Gap on Far Field Radiated Noise and Correlation with Local Flow Characteristics, AIAA-2003-3228.

Figures

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Wind tunnel airfoil models
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S822 airfoil model accuracy (difference between specified and measured coordinates)
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NLR anechoic wind tunnel with acoustically lined endplates and microphone array
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Acoustic source plots for the untripped NACA 0012 airfoil at 39.6 m/s and α=0° (array on pressure side) illustrating prominent trailing-edge emissions. Flow direction is from left to right. x [m] and y [m] are distances from the nozzle exit and the model centerline, respectively, in meters. The dynamic range is shown on the vertical scale in dB. Figures 5, 6, and 9 are similarly labeled.
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Acoustic source plot (left) indicating noise source locations in the plane of the model. The model contour is indicated by the (black) vertical rectangle. Flow moves from left to right. The (pink) horizontal rectangle indicates the trailing-edge integration contour used to translate acoustic source plots to airfoil noise spectra. For measurements with the turbulence grid, a leading-edge integration contour was used.
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Acoustic source plots for tripped S822 airfoil at 47.9 m/s and α=0° (array on suction side). Note the extraneous “corner sources” in contrast to the uniform sources shown in Fig. 4.
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Trailing-edge noise spectra for the S834 airfoil (array on suction side) plotted versus frequency in Hz. _ 22.4 m/s; _._ 32.0 m/s;[[ellipsis]] 47.9 m/s. As explained in the text under Extraneous Noise Sources, upper limits are indicated by the absence of a plotting symbol. Symbols indicate absolute noise levels.
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Trailing-edge noise spectra for S822 airfoil at 32 m/s. _ array on pressure side; _._ array on suction side. Note the symmetry about the chord, suggesting uniform directivity
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Leading-edge noise from SD2030 airfoil with trip, with turbulence grid, at a tunnel speed of 32.0 m/s and α=18° (array on suction side). Note the dominance of the leading-edge sources
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Leading-edge noise spectra for S834 airfoil (array on suction side). _22.4 m/s; _._ 32.0 m/s;[[ellipsis]] 47.9 m/s. Note that the levels are much higher than the trailing-edge noise spectra shown in Fig. 7.
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Normalized trailing-edge noise spectra for the S834 airfoil (array on suction side) plotted versus Strouhal number, St=f⋅i÷U. _ 22.4 m/s; _._ 32.0 m/s;[[ellipsis]] 47.9 m/s
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Normalized leading-edge noise spectra for tripped S822 (left) and S834 (right) airfoils (array on suction side). _ 22.4 m/s; _._ 32.0 m/s;[[ellipsis]] 47.9 m/s; __ 63.9 m/s
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Trailing-edge noise spectra for the NACA 0012 airfoil at 55.5 m/s. _ NLR data (array on suction side); _._ NASA data 7
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Narrowband trailing-edge noise spectra for three untripped airfoils that showed intense tones (U=22.4 m/s;α=10° for S834, α=0° for SG6043 and SD2030)
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Narrowband trailing-edge noise spectra for S834 airfoil at 22.4 m/s and α=10° as a function of trip thickness on pressure side (PS) and suction side (SS). A thin line indicates that these spectral values are an upper limit for the trailing-edge noise level.
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A-weighted overall trailing-edge noise levels at 32 m/s
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A-weighted overall leading-edge noise levels at 32 m/s. Airfoils are presented from left to right in the order of decreasing thickness (and increasing inflow turbulence noise at α=0°).

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