OpenFAST - OC4 DeepCwind Semi-Submersible input files


My thesis is about structural control of the OC4 Semi-Submersible Wind Turbine and in order to validate my model, I’m using OpenFAST.
In this case I need the input files including primary.fst, HydroDyn, AeroDyn and etc (e.g. something like those which were needed in FAST V7 with the format of NRELOffshreBsline5MW) about OC4 project according to the Technical Report NREL/TP-5000-60601 which I wish you could help me finding them.

Best regards,

Dear Ali,

An OpenFAST model of the NREL 5-MW baseline wind turbine atop the OC4-DeepCwind semisubmersible is available in the OpenFAST r-test, see: … St_WavesWN.

Best regards,

Hello, dear Dr.Jonkman

First of all, I appreciate your compassionate response and it helped me a lot, but I have two more questions to ask.
As I mentioned before I used the input test25.fst in the FAST.V8 to verify my model (OC4 semi-submersible) and I attached my displacements results (as pictures) in the following.
Here is a short summary of what I did to get the results of my model:

  1. I modeled the OC4 semi-submersible in the ANSYS-AQWA and I obtained the Mass, Damping and Stiffness matrixes.
    2.Then I stablished my equations of motion in the Simulink-MATLAB and I obtained the results of displacements.
    3.finally I checked the results with the displacements of what I got from FAST.V8.

So here is my first question: As you can see in the two following pictures, the results from what I did is not compatible with the results of the FAST, so I wanted to know if you have any suggestions for me to fix this issue.

Furthermore, my second question is about the results of the FAST in the time zero which do not start with zero and have a certain value (specially in surge and pitch motions as you can see in the pictures). Actually my question is that if FAST is following any special initial conditions in the time zero or not!

Best regards
Qe01.tif (163 KB)
Qe02.tif (188 KB)

Dear Ali,

Regarding your second question, the initial platform surge and pitch displacements are set in the ElastoDyn input file. In Test25, these are set to PtfmSurge = 5 m and PtfmPitch = 1.9deg as an example. You can change them to be whatever you want.

Regarding your first question, I would expect it to be difficult to assess what is different based solely on time-series responses from combined wind and wave excitation. I would suggest comparing inputs directly (like mass, stiffness, and damping matrices), or outputs that are simpler than time series, e.g., natural frequencies or RAOs, or time-series responses that are simpler, e.g., free decay in the absence of wind/waves, response to steady wind (without waves), response to periodic waves.

Best regards,