Stability analysis
Stability analysis
SIMA software includes modelling capabilities that allows building a complete and accurate physical representation of a floater, based on a SIMO model. The static stability of the model can be studied through the calculation of the equilibrium position, GZcurves or stability maps.
Modelling capabilities

Nonlinear hydrostatic force model
 Ballast tank system
 Position dependent wind and current coefficients
 All other SIMO force models, like anchor lines
 The force models above are also available for time domain simulations.
The force models above are also available for time domain simulations.
Nonlinear hydrostatic force model
The model used to compute the exact buoyancy forces and moments acting on the vessel is based on the following:
 Hull geometry is described as a STL file (watertight triangular panel mesh)
 The mesh is cut exactly at the free water surface
 The surface integrals are computed analytically for each wetted panel
Ballast tanks system
Each tank and/or compartment geometry is described as a STL file. Total gravity force and mass matrix are due to fluid in each tank are computed. The following features are included:
 Freesurface effect is included
 Volume of ballast tank can easily be modified
 The mesh is cut exactly at the free fluid surface
 The surface integrals are computed analytically for each panel
 Damaged tank model is available
Position dependent wind and current coefficients
Wind and current force coefficients can be provided by the user as a function of four parameters:
 Relative wind/current direction
 Floater vertical position
 Floater roll angle
 Floater pitch angle
For a given floater position and wind/current direction, the force coefficients are interpolated linearly from the data set.
Calculation possibilities
Different calculation possibilities are available to study the static stability of a system. Advanced postprocessing of results, graphics and plots are possible with external python scripts.
 Static equilibrium calculation (with the possibility to restrain desired degrees of freedom)
 Calculation of GZcurve: equilibrium is computed for each point of the curve. The azimuth angle and the rotation angles are defined by the user.
 Calculation of the stability map (twodimensional GZcurve). Equilibrium is computed at each grid point.