Hello,
I have a question regarding the reynolds numbers used, in the generation of steady airfoil coefficients,for the reference turbine NREL 5MW. In the chapter 2 of the document “Definition of a 5-MW Reference Wind Turbine for Offshore System Development”, it is mentioned that the blade structural properties are based on DOWEC LM blade. In the document “DOWEC 6 MW Pre-Design”, the steady airfoil coefficinets are generated for the airfoils DU40, DU35, DU30, DU25, DU21 at Re 7E6 and for NACA64 at Re 6E6. However, for the NREL 5MW reference turbine, the steady airfoil coefficients are generated at Re 0.75E6, for all the airfoils (as mentioned in the arifoils *.dat files). I did not found the reason for consideration of constant Reynolds number through out the blade span. It would be very helpful if someone could provide me some information on this.
Thanks in advance.
Best Regards,
Chaitanya Majjari
Dear Chaitanya Majjari,
I dug into this a bit and found that the original airfoil data files in the old AeroDyn format did not contain Reynolds number. Instead, as described in the NREL 5-MW specifications report (nrel.gov/docs/fy09osti/38060.pdf), and as stated in the files, the uncorrected (two-dimensional) airfoil data simply came from the DOWEC study, and the airfoil data contained within the file simply contain the three-dimensionally corrected data (for rotational augmentation etc.). When these airfoil data were converted to the new AeroDyn v15 format, the Reynold’s number seems to have been assigned randomly, as it is not currently used by AeroDyn v15. That is, the Reynold’s number was never specifically treated and is only assigned a value in the AeroDyn-v15-formatted airfoil data files out of necessity.
Best regards,
Hello Mr.Jason Jonkman,
First of all I wish you Happy New Year!!!
Thank you very much for your time and effort to reply. The information, you have provided is very helpful to me. I’m implementing the three dimensional correction method dynamically in a load simulation tool, for that I need the steady airfoil coefficients without correction for rotational augmentation. At first, I wondered to find the same reynolds number for all the airfoils, in the NREL 5MW wind turbine aifoils data. However, I’m also referring to DOWEC 6MW predesign document at the same time for certain turbine properties of NREL 5MW, which helped me abit. I just needed some confirmation, which you have provided me.
Best Regards,
Chaitanya Majjari
Hello,
I’m using FAST v7.02 to perform a time-marching simulation on a small wind turbine (radius = 2.33m). I’m currently using Prof. Selig’s airfoil series (SG 6040, 6041, 6042, 6043) and used AirfoilPrep to extrapolate the airfoil data to the relevant range of the AoA in the required AeroDyn format. The airfoil data I’ve extrapolated is for varying Reynolds numbers from 100,000 to 500,000 for each of the 4 airfoils.
I tried to input multiple tables into a single airfoil input file, however, I believe, the table formatting is inconsistent and subsequently AeroDyn is unable to read through the lines. Here’s the format I’ve followed for inputting 3 tables (of varying Re no. [100,000; 150,000; 200,000]) in a single input file, for a single airfoil design:
Any suggestions on the input file format? Or how I could potentially include multiple Re no. data in a single input file?
SG6042 airfoil data for 45% radius from hub.
Data came from PROPID.
3 Number of airfoil tables in this file
0.1 Table ID parameter, Re in millions
13 Stall angle (deg)
0 No longer used, enter zero
0 No longer used, enter zero
0 No longer used, enter zero
-8.5876 Angle of attack for zero Cn for linear Cn curve (deg)
2.9519 Cn slope for zero lift for linear Cn curve (1/rad)
1.1122 Cn at stall value for positive angle of attack for linear Cn curve
-0.8000 Cn at stall value for negative angle of attack for linear Cn curve
-5.00 Angle of attack for minimum CD (deg)
-0.0431 Minimum CD value
-180.00 0.000 0.2845 0.0000
-170.00 0.484 0.3043 0.4000
-160.00 0.969 0.3609 0.5897
-150.00 1.012 0.4464 0.4968
-140.00 0.744 0.5485 0.3588
-130.00 0.552 0.6523 0.2973
-120.00 0.391 0.7422 0.2659
-110.00 0.244 0.8037 0.2452
-100.00 0.111 0.8253 0.2251
-90.00 0.000 0.8000 0.2000
-80.00 -0.111 0.8253 0.1909
-70.00 -0.244 0.8037 0.1741
-60.00 -0.391 0.7422 0.1531
-50.00 -0.552 0.6523 0.1301
-40.00 -0.744 0.5485 0.1025
-30.00 -1.012 0.4464 0.0529
-20.00 -0.869 0.2898 -0.0644
-10.00 -0.186 0.0679 -0.0802
-5.00 0.156 0.0100 0.0000
-4.00 0.214 0.0100 0.0000
-3.00 0.271 0.0100 0.0000
-2.00 0.327 0.0100 0.0000
-1.00 0.382 0.0100 0.0000
0.00 0.437 0.0066 0.0000
1.00 0.491 0.0160 0.0000
2.00 0.545 0.0224 0.0000
3.00 0.602 0.0291 0.0000
4.00 0.659 0.0298 0.0000
5.00 0.714 0.0257 0.0000
6.00 0.769 0.0217 0.0000
7.00 0.824 0.0187 0.0000
8.00 0.877 0.0179 0.0000
9.00 0.931 0.0165 0.0000
10.00 0.983 0.0187 0.0000
11.00 1.034 0.0214 0.0000
12.00 1.086 0.0263 0.0000
13.00 1.136 0.0374 0.0000
14.00 1.185 0.0530 0.0000
15.00 1.235 0.0705 0.0000
16.00 1.284 0.0899 0.0000
17.00 1.334 0.1164 0.0000
18.00 1.383 0.1447 0.0000
19.00 1.433 0.1748 0.0000
20.00 1.483 0.2067 0.0000
21.00 1.532 0.2417 0.0000
22.00 1.582 0.2786 0.0000
23.00 1.631 0.3173 0.0000
24.00 1.681 0.3580 0.0000
25.00 1.730 0.4007 0.0000
30.00 1.445 0.4464 -0.0709
40.00 1.063 0.5485 -0.1296
50.00 0.789 0.6523 -0.1532
60.00 0.558 0.7422 -0.1684
70.00 0.348 0.8037 -0.1815
80.00 0.159 0.8253 -0.1928
90.00 0.000 0.8000 -0.2000
100.00 -0.111 0.8253 -0.2251
110.00 -0.244 0.8037 -0.2452
120.00 -0.391 0.7422 -0.2659
130.00 -0.552 0.6523 -0.2973
140.00 -0.744 0.5485 -0.3588
150.00 -1.012 0.4464 -0.4968
160.00 -0.969 0.3609 -0.5897
170.00 -0.484 0.3043 -0.5000
180.00 0.000 0.2845 0.0000
0.15 Table ID parameter, Re in millions
13.00 Stall angle (deg)
-9.9867 Zero Cn angle of attack (deg)
2.6756 Cn slope for zero lift (dimensionless)
1.0734 Cn extrapolated to value at positive stall angle of attack
-0.8000 Cn at stall value for negative angle of attack
-5.00 Angle of attack for minimum CD (deg)
-0.0566 Minimum CD value
-180.00 0.000 0.1871 0.0000
-170.00 0.467 0.2232 0.4000
-160.00 0.934 0.3267 0.5644
-150.00 1.025 0.4846 0.5108
-140.00 0.831 0.6763 0.4166
-130.00 0.673 0.8773 0.3842
-120.00 0.513 1.0611 0.3730
-110.00 0.343 1.2031 0.3649
-100.00 0.167 1.2836 0.3499
-90.00 0.000 1.2900 0.3225
-80.00 -0.167 1.2836 0.2967
-70.00 -0.343 1.2031 0.2590
-60.00 -0.513 1.0611 0.2147
-50.00 -0.673 0.8773 0.1681
-40.00 -0.831 0.6763 0.1190
-30.00 -1.025 0.4846 0.0543
-20.00 -0.812 0.2858 -0.0605
-10.00 -0.100 0.0575 -0.0445
-5.00 0.256 0.0100 0.0000
-4.00 0.297 0.0100 0.0000
-3.00 0.341 0.0100 0.0000
-2.00 0.385 0.0100 0.0000
-1.00 0.430 0.0100 0.0000
0.00 0.474 0.0013 0.0000
1.00 0.519 0.0101 0.0000
2.00 0.563 0.0161 0.0000
3.00 0.608 0.0188 0.0000
4.00 0.653 0.0196 0.0000
5.00 0.698 0.0196 0.0000
6.00 0.743 0.0189 0.0000
7.00 0.789 0.0175 0.0000
8.00 0.835 0.0171 0.0000
9.00 0.882 0.0174 0.0000
10.00 0.929 0.0177 0.0000
11.00 0.976 0.0198 0.0000
12.00 1.024 0.0251 0.0000
13.00 1.073 0.0361 0.0000
14.00 1.123 0.0522 0.0000
15.00 1.173 0.0700 0.0000
16.00 1.222 0.0895 0.0000
17.00 1.272 0.1160 0.0000
18.00 1.321 0.1442 0.0000
19.00 1.371 0.1743 0.0000
20.00 1.420 0.2062 0.0000
21.00 1.470 0.2411 0.0000
22.00 1.519 0.2780 0.0000
23.00 1.569 0.3167 0.0000
24.00 1.619 0.3574 0.0000
25.00 1.668 0.4000 0.0000
30.00 1.465 0.4846 -0.0726
40.00 1.187 0.6763 -0.1493
50.00 0.961 0.8773 -0.1963
60.00 0.733 1.0611 -0.2348
70.00 0.490 1.2031 -0.2694
80.00 0.239 1.2836 -0.2996
90.00 0.000 1.2900 -0.3225
100.00 -0.167 1.2836 -0.3499
110.00 -0.343 1.2031 -0.3649
120.00 -0.513 1.0611 -0.3730
130.00 -0.673 0.8773 -0.3842
140.00 -0.831 0.6763 -0.4166
150.00 -1.025 0.4846 -0.5108
160.00 -0.934 0.3267 -0.5644
170.00 -0.467 0.2232 -0.5000
180.00 0.000 0.1871 0.0000
0.20 Table ID parameter, Re in millions
13.00 Stall angle (deg)
-12.1582 Zero Cn angle of attack (deg)
2.6822 Cn slope for zero lift (dimensionless)
1.1778 Cn extrapolated to value at positive stall angle of attack
-0.8000 Cn at stall value for negative angle of attack
-5.00 Angle of attack for minimum CD (deg)
-0.0742 Minimum CD value
-180.00 0.000 0.1887 0.0000
-170.00 0.498 0.2247 0.4000
-160.00 0.996 0.3282 0.5977
-150.00 1.085 0.4859 0.5344
-140.00 0.867 0.6775 0.4277
-130.00 0.694 0.8783 0.3892
-120.00 0.525 1.0618 0.3750
-110.00 0.348 1.2036 0.3655
-100.00 0.169 1.2839 0.3500
-90.00 0.000 1.2900 0.3225
-80.00 -0.169 1.2839 0.2968
-70.00 -0.348 1.2036 0.2595
-60.00 -0.525 1.0618 0.2159
-50.00 -0.694 0.8783 0.1703
-40.00 -0.867 0.6775 0.1221
-30.00 -1.085 0.4859 0.0569
-20.00 -0.846 0.2825 -0.0627
-10.00 -0.047 0.0447 -0.0224
-5.00 0.352 0.0100 0.0000
-4.00 0.396 0.0100 0.0000
-3.00 0.440 0.0100 0.0000
-2.00 0.485 0.0100 0.0000
-1.00 0.530 0.0100 0.0000
0.00 0.575 0.0100 0.0000
1.00 0.621 0.0075 0.0000
2.00 0.666 0.0136 0.0000
3.00 0.711 0.0171 0.0000
4.00 0.757 0.0185 0.0000
5.00 0.803 0.0183 0.0000
6.00 0.849 0.0168 0.0000
7.00 0.896 0.0158 0.0000
8.00 0.943 0.0148 0.0000
9.00 0.990 0.0139 0.0000
10.00 1.038 0.0138 0.0000
11.00 1.086 0.0151 0.0000
12.00 1.134 0.0207 0.0000
13.00 1.184 0.0327 0.0000
14.00 1.233 0.0501 0.0000
15.00 1.283 0.0693 0.0000
16.00 1.332 0.0902 0.0000
17.00 1.382 0.1168 0.0000
18.00 1.431 0.1451 0.0000
19.00 1.481 0.1752 0.0000
20.00 1.531 0.2072 0.0000
21.00 1.580 0.2422 0.0000
22.00 1.630 0.2791 0.0000
23.00 1.679 0.3179 0.0000
24.00 1.729 0.3587 0.0000
25.00 1.778 0.4014 0.0000
30.00 1.550 0.4859 -0.0762
40.00 1.238 0.6775 -0.1537
50.00 0.992 0.8783 -0.1994
60.00 0.749 1.0618 -0.2365
70.00 0.497 1.2036 -0.2700
80.00 0.241 1.2839 -0.2997
90.00 0.000 1.2900 -0.3225
100.00 -0.169 1.2839 -0.3500
110.00 -0.348 1.2036 -0.3655
120.00 -0.525 1.0618 -0.3750
130.00 -0.694 0.8783 -0.3892
140.00 -0.867 0.6775 -0.4277
150.00 -1.085 0.4859 -0.5344
160.00 -0.996 0.3282 -0.5977
170.00 -0.498 0.2247 -0.5000
180.00 0.000 0.1887 0.0000
Thank you for the help.
Sincerely,
Angadvir Paintal
Dear Angadvir,
Test15 through Test17 in the FAST v7.02 CertTest are models of the SWRT turbine that uses airfoil data across a range of Reynolds number. I suggest you use those examples for the required format.
Best regards,
Take care with this machine:
I read: Rated Power at 11.4 m/s and 5MW. This means a cp of 0.442.
If it is a gearbox machine it is extremely questionable. IMO impossible.
0.442 can be maybe the optimum cp- but at RP the TSR drops and one will get maybe 0.40.
OK- if the machine rotates with a tip speed of 110 m/s then it will work.
Anyway- the machine is 400 W/m^2 and the efficiency for a high-wind-machine is lower.
Next: the 2D-airfoil-Reynolds-Number is the most important number of a rotor. If you ignore -the rotor/machine will fail.
If you use the “Optimum Betz Shape” for a rotor blade the Re-Number will be in reality a constant (Except very tip and root).
For the structure people it’s a desaster, but it is often done.
Next: Pretty often the error is made that for the rotor the Reynolds Number is taken where machine reaches R.P…
This provides huge problems.
An example:
When a machine reaches R.P at 12m/s, then it’s most probably around Wind Class III - Average Wind is 7.5 m/s.
This means that 2D-Airfoil data must work from about a Wind speed of >= 5.0 m/s.
The Reynolds number is there less or more half of the Re-number at Rated speed (depending on machine control).
That has to be determined iteratvely and that’s the optimization loop.
Kind regards
Hermann
BTW- The Re-problem is the reason why I published airfoils for small WTs.
Hi
I have collected my wind turbine data and I want to import it into FAST to do the simulation
But my question is, does it matter which tests I work with (Test01 to Test26 in the certtest folder of FAST software)?
Will I get different results if I enter my input data into two different tests?
Dear @Ali.Rouhbakhsh,
The various FAST CertTest or OpenFAST r-test examples are based on wind turbines of various configurations and sizes. If you are modeling a wind turbine that is different than any of these examples, I would pick the example (test case) that most closely resembles the wind turbine whose data you are trying to simulate and edit the input files based on your own data accordingly.
Best regards,