FAST v8 FOWT model linearization with FAST v7

Wind & Water Computer-Aided Engineering Software Tools
1

Dear all,

I would like to linearize a floating wind turbine model, but the files are in FAST v8 format. Thus, I was wondering if there is any matlab function to convert FAST v8 files into FAST v7 format. Or if someone did this conversion before. Any suggestion is also welcome.

Thanks in advance,
Joannes

2

Dear Joannes,

NREL has not provided scripts that convert FAST v8 models into FAST v7. However, the FAST v7 to FAST v8 conversion scripts that NREL has provided in the MATLAB Toolbox could probably be modified to convert the other way (with a bit of work).

Best regards,

3

Dear Jason,

Thanks for your kind reply. Before developing the conversion script, I started doing it manually. I have done the conversion of AeroDyn, Blade and .fst files. But I found dificulties in platform file to know how it is achieved the effective diameter (PtfmDiam) and the meaning of the parameters for mooring lines definition (LRadAnch, LAngAnch, LDpthAnch,…).

Thank you in advance,
Joannes

4

Dear Joannes,

In the platform input file of FAST v7 for the undocumented capability for floating platforms (PtfmLdMod = FltngPtfmLd):

  • PtfmDiam = member diameter used in the viscous-drag term from Morison’s equation (only a single vertical strip-theory member through the tower centerline is available)
  • LRadAnch = Radius from the undisplaced tower centerline to the anchor location
  • LAngAnch = Angle about the vertical zi axis from the xi axis to the anchor location
  • LDpthAnch = Depth below the mean sea level to the anchor location
  • LRadFair = Radius from the undisplaced tower centerline to the fairlead location on the undisplaced platform
  • LAngFair = Angle about the vertical zi axis from the xi axis to the fairlead location on the undisplaced platform
  • LDrftFair = Draft below the mean sea level to the fairlead location on the undisplaced platform

Regarding the mooring lines, you’ll noticed that FAST v7 only supports individual lines connecting the platform to the seabed (without line-to-line interconnections) and the lines are specified in cylindrical coordinates.

Best regards,