Mooring modelization on openfast

Wind & Water Systems Engineering Software Tools
1

Hello,

I currently work on motions of an offshore platform due to waves on openfast, so I already use Hydroyn and Elastodyn. I would like to add a mooring system but I ‘m not sure how to do it.
I saw that there is a module named Moordyn, in which I can define mooring lines and their properties and I also read on documentation that it’s possible to add a mooring stiffness matrix in AddClin (in the input file of Hydrodyn). So here are my questions : if I choose to run Moordyn, should I add the linear mooring stiffness matrix in Hydrodyn too ?
If yes, I found two methods to obtain this matrix : I read something about wamit files that have to be set to zeros and a linearization analysis, thanks to we get a DspCMat and I would like to know if this method is still available on openfast. The second option I found is to use a python module MAP++, which seems to give the linear stiffness matrix in output. Is it right ? In this case, should I use MAP++ instead of, or in addition to, Moordyn ?

Best regards,

Julie Marchebois

2

Dear Julie,

If you model the mooring system in one of OpenFAST’s mooring modules (MAP++, MoorDyn, or FEAMooring) then you don’t additionally need to define the mooring stiffness matrix through AddCLin in HydroDyn.

We generally recommend that you use MoorDyn if you want to model mooring dynamics in OpenFAST and MAP++ if you want to model mooring quasi-statics in OpenFAST.

I hope that helps.

Best regards,

3

Dear Mr,

Thank you for your quick answer, I now better understand !

Best regards,

Julie Marchebois