How to input platform motions time series and observe the responses.

Hello,
I am now working on Floating Offshore wind turbine modelling. I have to give FAST the platform motions as an input in order to see the responses caused by effect of floater motion. I have been using FAST for a while, but only see that FAST can give initial displacement(s). So, I would like to ask is there any way to input floater motions to FAST?
Thank you so much,
Best Regards,
Danupon Subanapong

Dear Danupon,

You cannot directly specify 6-DOF motion of the platform in FAST / OpenFAST without customization of the source code.

For the 3 platform translation modes, you can use FAST v7’s Seismic module to prescribe time histories of motion–please see my post dated Aug 29, 2012 in the forum topic found here for more information: http://forums.nrel.gov/t/software-releases/522/1.

Related questions have been discussed on this forum e.g.:
http://forums.nrel.gov/t/control-for-scaled-down-5mw-nrel/1087/1
http://forums.nrel.gov/t/imposing-estimated-motion-to-bottom-of-the-tower/1361/2
http://forums.nrel.gov/t/rigid-wind-turbine-with-harmonic-motions/685/6

Best regards,

Dear Jason Jonkman,
Thank you so much for your quick reply. I understood that it is not possible in FAST/OpenFAST. However, I know that FAST has interface with Orcaflex. In Orcaflex, the motions can be specified as input. So, the tower load responses can be obtained from FAST output. However, as far as I’ve tried it has not been successful yet. Can you please give me some suggestion? I wonder if I can do this way or not.
Best Regards,
Danupon Subanapong

Dear Danupon,

I’m not familiar with that functionality of OrcaFlex, but I would be surprised if the motion of the platform in FAST / OpenFAST could be controlled by OrcaFlex. This is because the FAST / OpenFAST interface to OrcaFlex is set up to pass the platform motions from FAST / OpenFAST to OrcaFlex and the hydrodynamic and mooring applied loads are passed from OrcaFlex to FAST / OpenFAST.

Best regards,