I downloaded FAST v7.02 of one version named FAST_v7.02.00d-bjj_AeroDyn_v13.00.02a-bjj_BladedDLLInterface.exe from this forum. And one of my seniors gave me FAST v7.02 of another version named FAST.exe. I tested them with NREL 5MW OC3-Hywind model, but I got two different results. The former showed constant power output and little oscillated platform displacement; while the latter showed the opposite. My senior remembered he downloaded FAST.exe from https://nwtc.nrel.gov/, but I can’t find it now. So I wonder if there are different versions of FAST v7.02, and which version should I choose?
Dear Yingyu Xu,
The standard FAST v7.02 archive is available from: wind.nrel.gov/public/jjonkman/FAST/ (see FAST_v7.02.00d-bjj_AeroDyn_v13.00.02a-bjj_BladedDLLInterface_OC3Hywind.exe).
Regardless, if I were starting a new project with FAST, I would use FAST v8. In FAST v8, the Bladed-style DLL control interface is a standard feature and no customizations are required to model the OC3-Hywind model appropriately. FAST v8 is available here: nwtc.nrel.gov/FAST8. Within FAST v8, The OC3-Hywind model is available as Test24.
There are several different executable versions of FAST v7.02.x. The standard version of FAST v7.02 on nwtc.nrel.gov does not have the Bladed DLL Interface as a standard option, thus any turbine that needs to use a DLL controller will need a different version. The BladedDLLInterface executable is FAST v7.02 compiled with the user control options coming from a Bladed DLL controller instead of Fortran source code linked with the executable. However, the OC3-Hywind model required some specialized code in addition to the Bladed DLL interface, so there is a 3rd executable version of FAST v7.02 for it: FAST_v7.02.00d-bjj_AeroDyn_v13.00.02a-bjj_BladedDLLInterface_OC3Hywind.exe. There is an executable in the FAST v7.02 archive for this model.
If you can, we recommend using FAST v8 so there is just one executable. FAST v8 has the Bladed DLL as a standard feature and the customizations for the OC3 Hywind model are standard options in the HydroDyn input file. The OC3 Hywind model is Test24 in the FAST v8 CertTest folder.
Also, we plan to discontinue support for FAST v7 after we add linearization to FAST v8. This will probably happen next year.
I actually intend to simulate a 10 MW wind turbine with FAST v7.02 with the Bladed-style DLL control interface, so I just use the standard version of FAST v7.02 and recompile it with the Bladed-style DLL control interface, and then make a test on the NREL 5 MW OC3 Hywind model.
According to http://wind.nrel.gov/public/bjonkman/DesignCodes/FASTCompilingInstructions.pdf, there are two ways of recompiling. And it turns out the FAST versions of Using the Command Line and Using Microsoft Visual Stadio are different. And these two versions are just like what I refered to in my former post.
Even if I use FAST v8, I still need to recompile it with different DLL controllers, then there are still two ways to choose. So, which version is more proper?
There should not be differences in results (other than small numerical roundoff-type differences) in the two methods of compiling the same source files in the instructions you mention. If you are compiling FAST v7.02 for the Bladed DLL, make sure you follow the instructions in the section “Creating FAST with the User-Defined Control Options for Interfacing with GH Bladed-style DLLs” and make sure you use the appropriate source files in your Visual Studio project. I suspect you are not using the same source files.
You do not need to recompile FAST v8 to use different DLL controllers. You merely select the appropriate control options in the ServoDyn input file and specify the DLL you wish to use.
Thanks for your reminding. I did use different source files to compile and I didn’t realize.