No Wind Condition for OC4 - Semi type

Good Day,

I am currently studying the 6 Dof motion for the OC4 Semi-Type Wind Turbine. From reading this forum, i have learned to run Test25 from the Cert test files.

After running the condition, i now want to change the parameters of the wind and waves to analyse the effect (via fft-white noise spectrum).

I basically want to set my wind speed to 0 mps or irregular wave only condition.
what i did was to set my compinflow to 0 (still air). and in my hydrodyn file, I set my waveMod to 3 (irregular wave) , significant waveheight (Hs) = 7.1 and Peak spectral period WaveTp = 12.1.

however, my FAST aborts with a fatal error.


Thank You,

To add on to the above question,

I have also tried to set the compAero to 0 to remove the aerodynamic loads from my calculation, to sort of represent 0 wind flow? any advise would be very much appreciated!

Basically i need to change the wind and wave conditions.
what i have tried so far is, :

  1. 1st condition - wind + Regular wave (H=4m Tp = 10s) . i set my’‘compinflow’’ condition to (1) - inflow wind 11.4m/s , i then went into hydrodyn to set my wave conditions, - wavemod (1) for regular waves, Hs - 4m Tp -10(s) i then ran FAST and generated PtfmSurge

  2. 2nd condition - Wind + Irregular Wave (Hs= 7.1 Tp=12.1 Gamma =2.2). same steps for wind condition, but for my wave condition i set my wavemod to (2) , Hs - 7.1 Tp -12.1, wave peak to 2.2 - I then ran FAST and generated PtfmSurge.

this is where my problem comes, when i analysed the results, i realised that the surge values for both conditions did not change at all? so what i did was i went back into the input values and decided to change my Hs Tp values into an absurd number like 10 and 10, but still no change to the
PtfmSurge values. I am pretty certain that they should vary between the conditions and i have a feeling my program is not reading the input values.
Please tell me if you know where i went wrong!

Hi guys, I’ve figured what i did wrong for the above problem highlighted in red. Basically when i tried to run FAST V8, i basically threw everything into the same file including the file 5MW_Baseline. What happened is that everytime i tried to RUN FAST, i edited my hydrodyn file in my folder but i did not edit the hydrodyn files inside 5MW_Baseline file. I am guessing FAST called on the original unedited files from inside the folder.


Dear Joel,

The name (including path) of the HydroDyn input file that is used when running FAST is set in the FAST primary input file.

To model a wind turbine in still air (wind speed = 0 m/s), you can set CompInflow = 0. In this case, you should disable the wake calculation within AeroDyn by setting WakeMod = 0.

To model a wind turbine in a vacuum (no aerodynamics), you should set CompAero = 0.

I hope that helps.

Best regards,

Dear Dr. Jonkman,

Following your advise,
To model a wind turbine in regular wave only condition H=4 T=10s

I switched CompInflow = 0 for still air and
disabled the wake calculation within AeroDyn by setting WakeMod = 0.
I also, went into Hydrodyn file and set wavemod = 1 (regular wave) , Hs = 4 and Tp = 10.
In my .FST file, compaero = 2.

i then ran the FAST calculations and got these values for the platform surge displacement.

Surge - Regular wave only - max = 6.431 m , min = -3.684 m and Std = 3.145 m

I know because the waves are in the heading seas direction, surge movement would be the largest displacement. does this regular wave only condition seem probable to you?

Thank you once again for your help,

Dear Joel,

I’m not really sure what you are asking me to comment on, but if you are using regular waves, presumably you’d want to look at the periodic response after all transients have died out. The surge response you indicate seems to describe the transient behavior; otherwise, I would expect that the max and min values would be much closer (assuming you’re not including second-order hydrodynamics).

Best regards,