Mooring lines

For different mooring system types, the footprint radius is the following:
• With Tension leg it is 30 m (based on Design considerations for tension leg platform wind turbines – ScienceDirect)
• With Taut it is the same as water depth.
• With Catenary it is (sqrt (line lenght^2 – depth^2)) based on the conservative assumption of a completely straight-stretched line.

Mooring lines are made of chain or wire rope and follow a curve that is described mathematically as a “catenary” from the point where they connect to the turbine to the point where they land on the seabed due to their weight. Along the seabed before reaching their anchors, allowing the use of drag embedment anchors, which are typically more affordable than anchors designed for vertical forces. Because of their curved profile and need for length on the seabed, catenary moorings generally have the longest lines and the largest anchor spacings. Youwind calculates the length directly with the bathymetry but with different scaling categories:
• With bathymetry between 0-200m, the scaling is 4.5x water depth,
• With bathymetry between 2-600m, the scaling is 4x water depth,
• and with >600m the scaling is 3.5x water depth.
For example, if the bathymetry is 100m, then the length of one line is 450m and if you have 4 lines the total mooring line length is 1800m.

Mooring lines are typically made of synthetic rope and have minimal contact with the seabed, relying on rope elasticity for their compliance, requiring anchors that can withstand both vertical and horizontal loads. In this analysis, we choose a 45° angle between the mooring line and the seabed to represent a minimal anchor spacing option for semisubmersible and spar platform types. Youwind calculates the Taut mooring line length with the bathymetry based on the assumption of 45° angle, as line length= √2* depth. For example, if the bathymetry is 100m the length of one line is 141m, and the total length of all the lines is 565m (4 units).

Tension Leg designs use high-tension mooring lines oriented vertically with anchors designed to withstand high vertical loads (e.g., suction pile anchors). The distance between anchors is approximately equal to the width of the floating platform, representing the minimum possible mooring footprint. These designs require a specific platform type with extra buoyancy. Youwind calculates the Tension leg mooring line length directly with the bathymetry. If the bathymetry is 100 the length of one line is 100 and if you have 4 lines, the total mooring line length is 400m.

When using the foundations’ categories: Spar Buoy, Semi-Sub Floating or Tensioned Leg Platform mooring lines are needed. After selecting the foundation category, you choose the mooring system: tension leg, taut and catenary included in our preset library. You will be able to choose the number of mooring tethering lines connected to the platform and seabed.