Stability
Considering a structure composed of different elements (bars, beams) with also all lump masses and buoyancy modules, different values are computed that give information about its stabilty:
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Center Of Gravity global coordinates (point G ),
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Center Of Buoyancy coordinates (point B),
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Displacement ( Disp ), i.e. the immersed volume (Note that every concentrated buoyancy is converted into an equivalent volume considering the water desnity),
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S_wa, i.e. the water plane area and its inertia momenta Ixx_wa , Iyy_wa (see Hydrostatic ),
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BG , G Mt, G Ml, G zx, G zy
The Metacenter positions are calculated as such:
- GMt = Ixx_wa/Disp - BG
- GMl = Iyy_wa/Disp - BG
where BG is the algebric distance between B and G.
Considering a rotation in a plane around the metacenter, the lever arm GZ represents the distance between G and its projection on the vertical straight line passing through B', the buoyancy center after inclination.
GZ is an algebric distance.
Note
This type of values may be found in the file "group_0.txt" generated by the solver. In case case, all elements included in the model take part in the diagnostics. For rigid bodies associated with a mesh of beams, the different diagnostics are povided in a dedicated ACSII file and all values may be post- processed with the GUI. It is then possible to check the stability of a floating body by imposing incremental rotations and wathcing the evloution of the different values.
