Hi,
This is Claudio. I am performing stability erifications for a floating platform composed of 4 small surface-piercing buoys (lower inverse cone + vertical cylinder) arranged horizontally in an square of 70 m x 70 m. I have performed GZ-curve calculations in Sesam (DNV-GL) and in another in-house software for two even-keel loading conditions (one with the waterline cutting the conical region and the other cutting the vertical cylinder). For, the first loading condition both Sesam and in-house matched their results, but for the second loading condition some differences appeared for the larger heeling angles.
So, I decided to use Maxsurf Stability to check. However, none of loading conditions' results matched with the other two software. (Notice that hydrostatic calculations: volumes, areas, center of bouyancy, etc. almost match among the three software) .
I know that Maxsurf is mainly focused on ships and catamarans...but is there any limitation for structures such as semi-submersibles or similar? In the animations that are displayed during the GZ curve calculations in Maxsurf Stability, it seems that the platform is heeled about the instantaneous CF of the whole platform (so, once a pair of floaters is completely out of water, the CF is shiftted to the CF of the other pair of floaters.
In the the other software. it seems that the axis of rotation is the centerline of eth wole structure...I understand that, perhaps, this is not the source of the problem, but I also understand that for in terms of displaced volume for multifloaters platforms, more than one solution is possible, for instance: all the four floaters partially submerged or only two floaters partially submerged and the other two completely out of water. How Maxsurf deals with this (large-heel angle) scenario? Any insights for the differences?
Obs: In my staudy case, the GZ curves of Maxsurf overestimated the stability (in Maxsurf, the vanishing stability angle was beyond 80° for the first loading condition, while for the other two software it was around 30°).
from what I remember you had completely different VCG in the MAXSURF model! :-)
with the correct VCG the results are essentailly identical