# Running FAST based on CFD turbulence fields

**URL:** <https://forums.nlr.gov/t/running-fast-based-on-cfd-turbulence-fields/774>\
**Category:** Computer-Aided Engineering Software Tools\
**Created:** [October 9, 2013, 3:56pm UTC](https://forums.nlr.gov/t/running-fast-based-on-cfd-turbulence-fields/774 "2013-10-09T15:56:13Z")\
**Posts on this page:** 1\
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**Author:** ![Bonnie.Jonkman](https://dub1.discourse-cdn.com/nrel/user_avatar/forums.nlr.gov/bonnie.jonkman/32/3230_2.png) [@Bonnie.Jonkman](https://forums.nlr.gov/u/Bonnie.Jonkman)\
**Post date:** [October 14, 2013, 8:58pm UTC](https://forums.nlr.gov/t/running-fast-based-on-cfd-turbulence-fields/774/2 "2013-10-14T20:58:47Z")

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Dear Bastian,

If I read this correctly, you want to produce wind inflow (turbulence) files that can be read in a FAST/AeroDyn simulation. in FAST, these files are actually read by a module called InflowWind, which accepts several different formats (or allows you to create your own format in a UserWind routine, assuming you code the subroutine to read the format you created.)

Most likely, you would create binary full-field turbulece files, such as the ones TurbSim generates (in a y-z plane at constant time intervals; with a .bts extension). The format is described in appendix D of the [TurbSim User’s Guide](http://wind.nrel.gov/designcodes/preprocessors/turbsim/TurbSim.pdf). I also have pulled out the TurbSim code (Fortran) that creates the wind files, and I made some modifications so that it should work outside TurbSim; you can find it here: [url][National Wind Technology Center's Information Portal | Wind Research | NREL](http://wind.nrel.gov/public/bjonkman/WriteTurbSimBinary.f90%5B/url%5D) You will need to use the NWTC Library to compile/use it. I’ve tried to make all the variables you’ll need to define as inputs. Note that TurbSim’s V array is only 3 dimensions: dimension 1 is time, dimension 2 is grid point, and dimension 3 is velocity component (U,V,W – see figure 3 in the TurbSim User’s Guide). The top of the routine indicates the numbering convention of the grid points (2nd component).

TurbSim also produces a Bladed-style FF binary file (.wnd, with a corresponding .sum file). This format is described in appendix E in the user’s guide; you can also read this post for help in generating them: [binary .wnd specification](http://forums.nlr.gov/t/binary-wnd-specification/180/1)

You can use the InflowWind module’s sample driver/test programs (one in Matlab, the other in Fortran) to verify that the files are generated correctly.

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