I have modeled a spar buoy with an elliptical tower and analyzed it in FAST 7. There is a very large heave response and therefore I want to add a heave plate to mitigate this heave response. Is there a way of including this in FAST 7 in the same way as in FAST 8.16?
The hydrodynamics capability of FAST v8 is vastly superior to that available in FAST v7. Without modification of the source code, you can model a heave plate in WAMIT, whose data is imported to FAST v7 for linear radiation/diffraction/hydrostatics. But all other heave-plate physics (viscous drag, linear damping, etc.) cannot be modeled without modification of the source code.
Thank you for the response. I have tried running the same support structure (spar buoy) with FAST 8 at rated wind speed, but I received a strange heave response.
I have used the quasi-static mooring system model for both FAST 7 and 8 and I have double checked that the platform dimensions match, so I am unsure as to the strange results of FAST8. Do you have any suggestions as to the large difference in the response of FAST 7 and 8?
Normally for the same/equivalent input settings, FAST v7 and FAST v8 produce very similar responses. Obviously, one of your models is set-up differently than the other, but I’m not sure what those differences might be. I’m assuming you assembled the FAST v7 and FAST v8 input files by hand? I suggest simplifying the model (removing DOFs and/or eliminating wind/wave excitation) to debug.