# Stability

# [STABILITY#]

A description of the various methods to calculate restoring forces can be found here.

This section is to be repeated for each floating body which uses either GZ-curves or the estimation method for the buoyancy point location.

[Stability1] means that the restoring forces acting on the body defined in section [Body1] will be calculated by the stability module. If this section is not given the restoring forces are determined with the hydrostatic spring matrix from the hyd-file.

The Stability field consists of the following keywords:

Keyword | Unit | Description | Options | Version |
---|---|---|---|---|

ApplyUserDefGZcurve | [-] | If true restoring curves for heave, heel and trim must be given. | Optional, if not present then false by default. | aNySim_v8.1 |

ApplyCalcGZcurve | [-] | If true the restoring curves are calculated with a Patran model of the vessel. | Optional, if not present then false by default. | aNySim_v8.1 |

HeelAngle | [deg] | Array with heel angles for the heel GZ-curve. | Compulsory if ApplyUserDefGZcurve is true. | aNySim_v8.1 |

GZHeel | [m] | Array with heel GZ-values. | Compulsory if ApplyUserDefGZcurve is true. | aNySim_v8.1 |

TrimAngle | [deg] | Array with trim angles for the trim GZ-curve. | Compulsory if ApplyUserDefGZcurve is true. | aNySim_v8.1 |

GZTrim | [m] | Array with trim GZ-values. | Compulsory if ApplyUserDefGZcurve is true. | aNySim_v8.1 |

Heave | [m] | Array with heave values for the heave restoring curve. | Compulsory if ApplyUserDefGZcurve is true. | aNySim_v8.1 |

HeaveSpring | [kN/m] | Array with restoring heave force values. | Compulsory if ApplyUserDefGZcurve is true. | aNySim_v8.1 |

PatranFile | [-] | Path and name of the file with the Patran model of the vessel. | Compulsory if ApplyCalcGZcurve is true. | aNySim_v8.1 |

HeelStep | [deg] | Heel step for the calculation of the heel GZ-curve. | Optional, if not present then 5 deg by default. | aNySim_v8.1 |

TrimStep | [deg] | Trim step for the calculation of the trim GZ-curve. | Optional, if not present then 5 deg by default. | aNySim_v8.1 |

HeaveStep | [m] | Heave step for the calculation of the heave restoring curve. | Optional, if not present then 0.25 m by default. | aNySim_v8.1 |

CoB0 | [m,m,m] | Local position of the buoyancy point (SF-midship-keel) at t= 0s | Optional, see below for the default value. | aNySim_v8.0 |

CoF | [m,m,m] | Local position of the floatation point (SF-midship-keel) | Optional, see below for the default value. | aNySim_v8.0 |

When both ApplyUserDefGZcurve and ApplyCalcGZcurve are not present cq false and the keyword ‘CoB0’ is not given then the coordinates of the buoyancy point will be deducted from the position of the CoG and the XB record of the hyfile.

SFCoBPos(1) = SFCoGPos(1) + XB

SFCoBPos(2) = 0.0

SFCoBPos(3) = SFCoGPos(3)

When both ApplyUserDefGZcurve and ApplyCalcGZcurve are not present cq false and the keyword ‘CoF’ is not given then the coordinates of the center of floatation will be deducted from the position of the CoG and the XF record of the hyfile.

SFCoFPos(1) = SFCoGPos(1) + XF

SFCoFPos(2) = 0.0

SFCoFPos(3) = SFCoGPos(3) (the z-coordinate is not used in the model)

## Aliases of the output signals of the stability module

Alias | Index 1 | Index 2 | Description | Version |
---|---|---|---|---|

'GZheel' | iBody | - | GZ-values of heel [m] | aNySim_v8.1 |

'GZtrim' | iBody | - | GZ-values of trim [m] | aNySim_v8.1 |

'C33' | iBody | - | Heave restoring spring [kN/m] | aNySim_v8.1 |

'CoBPos' | iBody | iMode | Local position of the buoyancy point in {SFCT} (3 modes, [m,m,m]) | aNySim_v8.0 |

'Fwght' | iBody | iMode | Weight forces at CoG in the local referential of the body in {SFCT} (6 modes, [kN,kNm]) | aNySim_v8.0 |

'Fbuoy' | iBody | iMode | Buoyancy forces at CoG in the local referential of the body in {SFCT} (6 modes, [kN,kNm]) | aNySim_v8.0 |