Mooring system

A floater has a mooring system to keep it in position. The mooring system is a part of the Support structure, but is it not a Support section.

General

Layout

The layout of the mooring lines, i.e. the angle of the mooring lines relative to the principal angle of the mooring system.

Options:

User defined:

The user defines the layout.

Auto (default):

The layout is automatically defined.

Principal angle

The principal azimuth angle of the mooring system. The azimuth angle of each mooring line is given relative to this angle. Thus, the angle of all mooring lines are changed by changing this angle.

An angle of 0 usually means in the platform forward direction, which is usually the upwind direction. Positive angles rotates the mooring lines clockwise.

  • Default value: 0
  • Unit: $°$
  • Range: -180 — 360

Seabed contact

Seabed interaction

The effect of contact with the seabed on the mooring lines.

Options:

None:

No effect of the seabed on the mooring lines.

Linear (default):

The seabed asserts a vertical lifting force on the mooring lines. The force increases linearly with depth into the seabed.

Seabed stiffness

The normal stiffness of the seabed material given per contact area when using a linear seabed model. I.e. the normal force on an element penetrating the seabed will be equal to this value times the element contact area (diameter*length) times the penetration depth. The unit of this value is N/m2/m or Pa/m.

The normal force acting on each element of the mooring line is lumped half to each of the nodes. Loads on an element that is partially below the seabed will be ramped proportional to how much of the element's centerline is below.

  • Default value: 100000
  • Unit: ${\text{N}} \over {\text{m}^3}$
  • Range: -∞ — ∞

Seabed shear stiffness

The seabed shear stiffness is used to find the horizontal friction force if the mooring line is in contact with the seabed. Default: 1E6 N/m^2/m

  • Default value: 1e+06
  • Unit: ${\text{N}} \over {\text{m}^3}$
  • Range: -∞ — ∞

Seabed friction coefficient

The seabed friction coefficient is used to find the horizontal friction force if the mooring line is in contact with the seabed. Default: 1.0.

  • Default value: 1
  • Unit:
  • Range: -∞ — ∞