User defined shear profile

Wind & Water Computer-Aided Engineering Software Tools
1

Hi,
I have been working on incorporating user defined shear exponents in IECWIND and have found that turbsim already has this capability. It appears from the turbsim code that there is also the means to have a USR (user) defined shear profile type, which has a file read-in in the GetUSR subroutine. Do you have any guidance/documentation on this functionality, I have not come across any reference to it in the manual, or did I miss something?

All the best,
Rebecca

2

Hi Rebecca,

TurbSim has a few features that I added to help with some projects I’ve previously worked on, but most of them haven’t been documented, yet. Some of the features require some work (especially more error checking) before I’m willing to support other people using them. :slight_smile: However, the user-defined wind profile is pretty straight forward:

WindProfileType = “USR”

  • This can be specified for any of the spectral models.
  • URef and RefHt input values are not used in this case.
  • The wind speed and direction values come from a lookup table at the end of the TurbSim input file. Here is a sample input file for TurbSim v1.50 (also v1.06.00) that uses this feature: wind.nrel.gov/public/bjonkman/Sa … rShear.inp
  • Heights in the table must be listed in increasing order. Only NumUSRz heights are read, so specify that value correctly!
  • TurbSim interpolates linearly between the heights specified in the table; it uses nearest-neighbor before the first and after the last values read.
  • The StdScale1, StdScale2, and StdScale3 parameters aren’t used with this feature, but they must be positive numbers to pass the error checking (you shouldn’t need to change them in the sample input file).

The summary file lists the wind speed and direction profiles that TurbSim uses, so check them to make sure they are what you expect.

[size=85]P.S. There is also a user-defined spectral model (spectra read from an input file) and a user-defined von Karman model.[/size]

3

Hi,

I am currently trying to implement several wind spectral models for offshore wind in Turbsim.
Is it possible to implement them without making changes to the Turbsim code?

Bonnie, you mentioned in your post above, that it is possible to include an user-defined spectral model read from an input file in Turbsim. Is there any sample file available or any user’s guide to implementing user defined spectra?

Thank you very much for your time! Best regards.

Maik

4

Hi, Maik.

My apologies for the long wait. I’ve been working on some big projects the last few months that have left me little time to read the forum.

The user-defined spectrum in TurbSim is an undocumented feature to get velocity spectra for the three wind components from a lookup table contained in a file called UsrSpec.inp. You can find a TurbSim input file that uses this feature here. This UsrSpec.inp file contains the IEC 61400-1, Ed. 3 Kaimal model for 12 m/s winds at 90 m hub height. You can modify it to use your own spectra.

Here are some basic instructions/comments:

  • To use the user-defined spectra, you enter “USRINP” for the spectral model in the TurbSim input file.
  • The spectra must be in a file named “UsrSpec.inp” and the file has to be in the directory from which you’re running TurbSim. (Note that it will only read NumUSRf lines of frequencies from the file, so be sure that number is specified correctly.)
  • TurbSim linearly interpolates the spectra to get the values it needs. If it needs a value for a frequency before the first one in the file or after the last one, it uses the nearest neighbor.
  • You can’t change the standard deviation from the TurbSim input file since it is determined by the spectrum. You can change the spectrum, and I’ve included some scaling factors in the UsrSpec.inp file to allow the amplitude to be easily scaled.
  • The model uses the parameters in the non-IEC Meteorological Boundary Conditions section of the input file so that you can adjust the coherence. I have set the inputs in the sample file to match the coherence in the IEC standard (large values for the input parameters IncDec* basically remove the spatial coherence for the specified component). Though it is close, it won’t give you exactly the same coherence as the IEC models because this coherence model uses local mean wind speeds instead of the hub-height mean wind speed at all points.

If you use this feature, I recommend that you thoroughly test the output to make sure it is working as you expect.