5MW FOWT linearization issue

Dear Dr. @Jason.Jonkman,

Thanks a lot for taking the time to do that!
I ran the simulation using the precompiled OpenFAST v.3.2.1 executable as well, and the that the simulation didn’t stop prematurely. However, I got an error

I mentioned that the “NUL” characters appeared with v.2.6, whereas with v.3.0 and v.3.2 it is fine.
I didn’t make any changes to those input files. I was just using OpenFAST that I compiled myself, but the double precision version.

I think I don’t need to compile OpenFAST myself, and just use the precompiled one since I am not modifying the source code. The only issue now is with the precompiled OpenFAST v3.2 executable above.

Best regards,

Dear @Amr.Hegazy,

I’m not sure what to recommend. When I run your input files with OpenFAST v3.2.1 I don’t receive the same error from MAP++. Here is what I see:

Best regards,

Dear Dr. @Jason.Jonkman

Thanks a lot for your help!
I got it to work fine. I still get those errors sometimes though, but at the end it works.

I was wondering how can I linearize at velocities close to the rated speed considering the negative damping? As CalcSteady doesn’t return a steady state solution. How did you do it yourself at V = 12 m/s and at the rated speed?

Best regards,

Dear @Amr.Hegazy,

Regarding the computation of a steady state solution, see some guidance provided in the Linearization chapter of the old FAST User’s Guide (FAST.pdf - Google Drive):

When trimming, also make sure that the condition you are trying to trim to is “reasonable”. For example, during Region 3 trim (TrimCase = 3), it may be impossible to find a rotor collective blade pitch angle at a given rotor speed and wind speed if the constant generator torque is too large. The steady state solution computation may become unstable if the initial guess of nacelle yaw is too large when trimming yaw (TrimCase = 1). During Region 2 trim (TrimCase = 2), the solution computation may also become unstable if your desired rotor speed is below the rotor speed that results in the maximum power coefficient at a given wind speed and rotor collective blade pitch angle. In this case, the only way to obtain a successful trim solution is to increase your desired rotor speed condition.

Does that help?

Best regards,