Stability

Static stability of a simple body with a ballast system, set up so the mechanics can be followed without the complexity of a real hull. In the SIMO task cube, the body BODY carries six ballast tanks. Each tank is given a position and an initial ballast quantity, and each has its own geometry from an STL file: cube10.stl for the four corner tanks, and cylinder.stl and cone.stl for the two on top. The hydrostatic stiffness is non-linear, computed from the hull geometry in cube100.stl, and quadratic wind and current coefficients are read from windCoefficient_forCubeExample.dat and currentCoefficient_forCubeExample.dat.

The custom editor task Simstab_UI wraps the model in a simplified user interface. Double-clicking Stability analysis opens an editor where the filling level of each tank is set directly, Compute equilibrium runs the workflow fetch_equilibrium_position_from_Initial_condition in Simstab_workflow, and the resulting equilibrium position is shown as X, Y, Z, Roll, Pitch and Yaw. The tank levels are driven through the variables initialBallastQuantity_Tank1 to initialBallastQuantity_Tank6, so changing a level in the UI, or in the ballast system editor under BODY, updates the equilibrium and the 3D view. Right-clicking Stability analysis and choosing open edit mode gives access to the UI itself. The verification task SimStabTest checks the equilibrium position against the expected values.

The STL geometries and coefficient files are in the storage task InputFiles, so the tank shapes can be swapped and the effect on the equilibrium studied directly.

stability ballast system ballast tanks static equilibrium hydrostatic stiffness STL geometry custom editor workflow

SIMO