TurbSim: incorrect flow angle at zero turbulence

Hi,

I encountered an inconsistency when generating FF wind fields using TurbSim:
Setting turbulence intensity (IECturbc) to 0 produces uniform wind fields that can easily be analyzed.
When setting a mean flow angle in the input file, for example VFlowAng = 5, the resulting wnd-file contains wind vectors, all with 0.2° uptilt only.
My wnd-reading and calculation of angle works, because if I use turbulent wind fields, say TI=10%, I get a mean uptilt of around 5°.

How can I produce FF wind fields with zero turbulence and correct flow angles?

Btw, shear seems correct for TI=0…

Best regards,
Stefan

Hi, Stefan.

The problem you describe is really an artifact of the scaling method used to store/retrieve data in the BLADED-style binary output files (".wnd" files). The scaling method doesn’t work very well (or at all!) when you have files with very low standard deviations or very high shears. I’ve made some modifications to the scaling in the past, which has helped a bit, but the method still has numerical issues in some cases. This is a big part of the reason we have added the “.bts” output format in TurbSim.

I recommend that you use the “.bts” output format if you can (it is available in AeroDyn v13.00.00a-bjj and the codes that link with it). It uses a much more accurrate scaling method.

Regards,
Bonnie

Hello,

I found the same problems that Stefan had. I have understood the solution but unfortunately it does not work in my case. It seems that AeroDyn continues to look for a *.wnd file and it does not accept the *.bts generated in TurbSim.

AeroDyn could not initialize. I am using latest versions of the codes:

  • FAST_v7.02.00d-bjj_AeroDyn_v13.00.02a-bjj_BladedDLLInterface_OC3Hywind.exe
  • AeroDyn_v13.00.02a-bjj
  • InflowWind v1.01.00b-bjj
  • NWTC Subroutine Library v1.07.00b-mlbI

It seems that these versions should work, I think. Do I have to switch any other input parameter to allow AeroDyn read this *.bts file?

Thank you for your help.

If you specify your wind file using the “.bts” extension in the AeroDyn input file, it should read it. If there is no file extension, it will assume it is a file ending in “.wnd” (because the files with “.wnd” extensions also require a file ending in “.sum”)

This is one of those error that I can not find even if it is in front of me!

Thank you Bonnie!