The static tension load in the mooring lines (for the Base Case single line mooring) was calculated for varying current velocity over the diurnal tidal cycle. The chart below illustrates the results of these calculations, showing that the minimum line tension was 445 kN at slack water (due to buoyancy forces), rising to 585 kN at peak flow (due to additional drag forces).
Orcina OrcaFlex was used to carry out dynamic analysis. OrcaFlex is a Marine 3D non-linear time-domain finite element program, which is used for static and dynamic analysis of a wide range of offshore systems including:
Risers and moorings
This software is used extensively in offshore oil & gas industry, as well as in marine renewables research:
Mooring design for wave energy converters
Modelling Currents & Tides
Two dynamic cases were investigated, the first for 5 m high waves (with a 10 second period), and the second for 10 m high waves (with a 10 second period). The results of the analysis for both the 5 m and 10 m wave cases are illustrated in the chart below, which shows that the peak dynamic load for the 5 m wave was 665 kN, increasing to 700 kN for the 10m wave case. The initial static load calculated using Orcaflex was 635 kN, which compared well with the 585 kN calculated in the static analysis described above.