Weird behavior

[jkoot1973]

I modeled a floater with WTG+tower on one of the columns. (similar to PPI or Technip INO15 floater. We have used the example floater from the RAFT package (VolturnUS-S_example.yaml) and kept the turbine + tower at (X,Y) = (0, 0). Basically we translated floater column + mooring + anchor coordinates in X direction. (all Columns have nearly same mass…meaning we would expect the weight of the turbine would result in pitch forward, but the opposite is the case). Running RAFT we now get this weird behavior(see picture below) in steady state (no wind, no waves).

What can be cause of this? Coordinate system of RAFT and pyHAMS not matching?

Thanks in advance Jasper Koot Siemens Gamesa

[mattEhall]

Hi Jasper, I think there may be an error in RAFT's off-diagonal hydrostatic terms that causes nonphysical results in designs that have asymmetric waterplane area relative to the origin. Another user identified issues like this. We will look into it.

[jkoot1973]

Thanks Matt. This gives good direction where to look.