Options for analysis of semi-taut mooring systems

[LennardMVF]

Hi,

In order to evaluate the feasibility of FOWTs with semi-taut mooring systems, it would be nice to be able to assess whether the connection point between the synthetic line and chain makes contact with the seabed and assess whether the loads on the anchor are purely horizontal. Does RAFT have any options for this? I saw that MoorPy has some methods to do this (getForces, getPositions, getAnchorLoads), but these all only work with MoorDyn output files, rather than RAFT simulation data. Is there anything that can be used?

Many thanks

[mattEhall]

Hi Lennard, many of the MoorPy functions work with a steady-state MoorPy mooring solution, so you can use them to get information about the equilibrium state of a MoorPy model within RAFT. For example, to get the position and forces on a node you could use something like:
model.fowtList[0].ms.pointList[11].r # position of point 11 in the mooring system
model.fowtList[0].ms.pointList[11].getForces() # forces of point 11 in the mooring system

The limitation is that these are from the steady (equilibrium) state in RAFT/MoorPy, since MoorPy is a quasi-static model and we haven't set up any approximations for dynamics for what you're looking for yet. For each of the things you're wondering about, you could move the floating platform into the worst-case position (with the FOWT.setPosition method), then query the MoorPy solution with the commands I showed above.

Matt

[LennardMVF]

I see, thank you very much for your response!