Validation of a Mooring System With Clump Weights for a Spar Floating Wind Turbine Model Using OpenFAST

Abstract This research focuses on analyzing three different mooring systems for a FWT mounted on a spar-buoy platform. Building on an initial realistic two-segment catenary mooring system, we introduce two innovative mooring configurations that incorporate the use of a clump weight at two different locations: one close to the seabed and the other close to the fairlead. The mooring configurations are evaluated under wave-only conditions. To assess these different mooring systems, we conducted 1:47 scale model experiments at the CEHIPAR ocean basin. These experiments are compared with a set of OpenFAST numerical simulations, where MoorDyn is implemented to model the mooring dynamics. The results demonstrate a good agreement of OpenFAST with MoorDyn compared to the experimental data in terms of platform motions, but small differences are found when comparing the mooring tensions. A discussion of the difficulty of scaling the axial stiffness of the line material is presented. With the inclusion of clump weights, the maximum tension in the lines under extreme conditions decreases by around 6% while maximum allowable motion limits remain acceptable. This research contributes significantly to the estimation of the change in FWT sea-keeping performance when these devices are attached to mooring lines.