Geometric Properties of the NREL 5-MW baseline blade

Hallo,

I currently try to retrace the definition of the blade properties used for the NREL 5MW Reference Wind Turbine. In specific I would like to understand where the values given in the CertTest\5MW_Baseline folder of the FAST v8.16 archive come from.
As mentioned in the report “Definition of a 5-MW Reference Wind Turbine for Offshore System Development” the blade properties are based on the values given in the report “Aeroelastic Modelling of the LMH64-5 Blade” by Lindenburg, C.

Using this information I managed it to understand how to obtain the distributed blade properties required for ElastoDyn.
However I get problems when trying to derive the blade properties required for AeroDyn v15.
While I am able to calculate the BlTwist and BlChord values given in the CertTest folder, I didn’t find any connection between the values in the reports and the values for BlCrvAC, BlSwpAC and BlCrvAng in the CertTest folder.

Could you tell me, how I can obtain the values for BlCrvAC, BlSwpAC and BlCrvAng?

Kind regards,
Paul Schünemann

Dear Paul,

The blades of the NREL 5-MW baseline turbine are not curved, so, BlCrvAng is zero.

BlCrvAC and BlSwpAC were set so as to obtain the proper offset of the aerodynamic center from the pitch axis. These were derived based on the values of AeroCent and StrTwst (= aerodynamic twist) from Table 2-1 in the NREL 5-MW specifications report: nrel.gov/docs/fy09osti/38060.pdf.

I hope that helps.

Best regards,

Dear Jason,

thank you very much for your answer and sorry for the late reply.

Your hint was really helpful, as I was now able to calculated the values of BlCrvAC and BlSwpAC based on your information. For that I used the values for PitchAxis and AeroRef given in your post from Sat Jan 29, 2011 4:28 am in http://forums.nrel.gov/t/nrel-5mw-rotor-geometry/330/3

However than I compared the values of PitchAxis from that post with the values given in die ElastoDyn Individual Blade Input File NRELOffshrBsline5MW_Blade.dat given in the CertTest folder of the FAST v8.16 archive. By doing this I found that the do not agree with each other (at least for the first couple of radius).

I think, this is because for the ElastoDyn file the relation PitchAxis = 0.5 - AeroCent from README_FAST8.pdf was used (with AeroCent from Table 2-1 in NREL 5MW definition). However, I think, this relation assumes that the Aerodynamic Reference Point AeroRef lies at 25% chord, which is not the case for the first couple of radius where the values of PitchAxis disagree between the ElastoDyn and the AeroDyn input file.

What do you think about this issue?
Do you agree with me, that it would be more appropriate to use the PitchAxis from the above mentioned post also in the ElastoDyn input file?

Kind regards,
Paul Schünemann

Dear Paul,

As described under “CompAero” in the FAST v8 ReadMe file (wind.nrel.gov/nwtc/docs/README_FAST8.pdf), ElastoDyn input PitchAxis is unused when CompAero=2 i.e. when AeroDyn v15 is enabled.

Best regards,

Dear Jason,

Thank you very much again for your really fast answer.
When reading it, I prompt remembered that I read this fact some time ago in the README file. I just forgot it and didn’t check this file before writing my last post.

Sorry for that and thanks again for your help.

Kind regards,
Paul Schünemann