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OpenFAST / openfast

Main repository for the NREL-supported OpenFAST whole-turbine and FAST.Farm wind farm simulation codes.
http://openfast.readthedocs.io
Apache License 2.0
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Airfoil Data #1936

Open EVElove444 opened 10 months ago

EVElove444 commented 10 months ago

In the given example of NREL5MW, have the data cl and cd of airfoil DU21 been tested and verified when Re=7000000 or Re=6000000? Is there any experimental data to support it?

jjonkman commented 10 months ago

Dear @EVElove444,

See a similar question asked and answered on our forum: https://forums.nrel.gov/t/original-nrel-5-mw-2d-airfoil-data/713. My understanding is that the original 2D airfoil data for the DU airfoils of the NREL 5-MW baseline wind turbine were wind tunnel tested between approximate -10 to +20 deg angle of attack and a Reynolds number of 7M.

Best regards,

EVElove444 commented 10 months ago

Hello, the answer you gave did not directly give the data of DU airfoil, angle of attack of -10 to +20 degrees and RE=7M wind tunnel test, such as the relationship between angle of attack and CL/CD, etc. Are there any references? Thank you again.

jjonkman commented 10 months ago

My post dated Jun 26, 2013 in the forum topic I linked to contains zip archive with the airfoil data you seek.

EVElove444 commented 5 months ago

Greetings, Do the aerodynamic data for the airfoil in the 5MW baseline file, which are presented at a Reynolds number of 7,500,000, originate from wind tunnel experiments and subsequently extrapolated to the range of -180-180°? Discontinuities in the drag coefficient are observed in the NACA64A17 airfoil input file between 4 and 12 degrees, as well as after 10 degrees, resulting in significant fluctuations in the lift-to-drag ratio. Is this typical? The discrepancy between the wind tunnel data and the calculated results utilizing XFOIL and SST transition models at the identical Reynolds number of 7500000 is substantial, and the ideal range of lift to drag ratios differs. Does this appear to be accurate?

jjonkman commented 5 months ago

Dear @EVElove444

The airfoil data of the NACA64 airfoil is actually for a Reynolds number of 6M.

Regardless, the DOWEC report from which the original 2D data came mentions the following:

the airfoil data for the NACA 64-618 as copied from appendix IV of Abbott and Von Doenhoff, apply to a Reynolds number of 6 million

These data were then extended to the full AoA range, as also mentioned in the DOWEC report:

For all airfoils measured coefficients were available between angles of attack of approximately -10° and +20°, depending on the airfoil. These coefficients were extended to -180° and +180° using results from the ECN tool StC (Stall Coefficients), release "MAR-2001"

The aspect ratio of the blade used for the StC calculations was (A) = 17, which is on the conservative side when comparing it with the PHATAS estimation (A) = 16.4.

The NREL version of the data includes corrections for rotational stall delay based on the Selig and Eggars method and to drag using the Viterna method.

Best regards,