Dear Dr. Jonkman,
I am trying to reproduce the load case 3.1 (steady wind and regular waves) from the OC4 phase 2 analysis of the DeepCWind floating wind turbine.
The issue is I get a Fatal Error due to an unstable model as I saw on other posts. I can just solve it by reducing the timestep of the main input file to make it work. But I followed the instructions given by the document “Load Cases for OC4 phase II” of 2013, found in the following link you provided in another post: https://drive.google.com/drive/folders/1DCtqqoRvu_kvof8mcagQ3imrK7xmOLv3
It stipulates that:
- DT output = 0.05 s, so the Nyquist frequency is 10 Hz,
- DT wind = 0.05 s in the wind paragraph (although it is written 0.1 s in Table 1: General Settings),
- and DT wave = 0.1 s.
I applied it, with DT wave = 0.1 s, DT wind = 0.05 s, and DT simulation of the main input file (.fst) = 0.05 s. In that case, the model is unstable and I get instantly a Fatal Error.
But if I reduce the DT simulation (.fst), I get a warning that DT wind cannot be less than DT simulation.
In the end, I cannot reproduce the load case 3.1 without having an unstable model, or I can do it but reducing DT wind to match DT simulation that I reduced to get a stable model.
I hope it is clear enough, and I thank ou in advance for your help so I can have a stable model reproducing exactly the load case 3.1.
Have a nice day,