Offshore wind turbine with monopile (DS and p-y curves)

Wind & Water Structural Analysis
1

Dear FAST community,

I am quite new in FAST and I am currently modeling an offshore wind turbine with a monopile. I derived the eigenvalues and modes shapes using BModes and a distributed springs model but, for now, I would like to perform time-domain simulations and compare the values of the eigen frequencies I get, namely BModes with distributed springs vs. FAST with distributed springs or FAST with p-y curves.

However, I read (@ Turbine-soil interaction. Influence on the mode shapes.) it was not possible yet to run FAST with a distributed springs model or the p-y curves. I downloaded the .f90 file with the user-defined subroutine UserTwrLd but I would like to know what are the changes to be made in the source code of FAST for using this routine (distributed springs). In which file(s) must this routine be written, when must it be called?

The following step would be to incorporate the p-y curves (which I have, ie. table of values + graphs) in the code, but I guess I would need to create a loop in the source code for re-computing the loads. Shall you please help me with that?

Thanks a lot. Best regards,

Loïc Maudoux

2

Dear Loic,

The forum topic you linked to provides a lot of guidance for introducing a distributed-springs foundation model into FAST v7 through the user-routine UserTwrLd(). As discussed in that topic, the provided UserTwrLd() could be modified for p-y curves in place of simple linear springs. Using your own UserTwrLd() routine will require a recompile of FAST v7 with your UserTwrLd() routine.

More guidance for building a FAST v7 model with a distributed spring or p-y foundation can be found in the following forum topic: Natural frequency of NREL DS monotower in OC3..

Best regards,

3

Dear Jason Jonkman,

First, thank you for your answer. I did not mention that i use FAST V8. Does the same rationale still apply?

Best regards,

Loic Maudoux

4

Dear Loic,

The forum topics referenced above apply to FAST v7. Regarding FAST v8, a similar question has been asked and answered in the following forum topic: Foundation Stiffness and damping in FAST v8.

Best regards,