Experimental comparison of a dual-spar floating wind farm with shared mooring against a single floating wind turbine under wave conditions

Shared mooring can potentially be a cost-reduction factor for future floating wind farms. To assess the effect of shared mooring on the response dynamics of floating wind turbines (FWTs), experiments have been conducted for two spar FWTs with a shared mooring configuration and for a single spar FWT with catenary mooring, both at a scale of 1:47. Various regular and irregular wave conditions were tested and only one wave heading was considered. From the test results, the response amplitude operators and response spectra of platform motions and statistics of mooring tensions are compared for the two configurations. In the extreme wave condition, the shared mooring configuration leads to a 40% increase in the platform surge motion compared with the single spar FWT. Still, the absolute offset is within allowable limits prescribed by power cables. The fairlead tensions of the anchor lines are not significantly increased in the shared mooring configurations, but the shared line shows extreme tension peak events that are seldom present in the anchor lines. This study demonstrates the technological promises and challenges of a shared mooring system from an experimental perspective. Results and videos are made available and can be used to validate numerical models.publishedVersio

Experimental and Numerical Study of the Influence of Clumped Weights on a Scaled Mooring Line

Recently, several experimental and numerical studies have underlined the advantages of adding clumped weights at discrete positions of mooring lines. To confirm the influence of these weights, an experimental study was performed for a 1:30 scale model of a mooring line. In this study, the clumped weight is modeled as a scaled disc placed at different positions along the mooring line. The series of experiments has been carried out at the CEHIPAR towing tank using a submerged studless chain both with and without clumped weights. The experiments consist of the excitation of the suspension point with horizontal periodic motions using different amplitudes and periods, where the mooring line’s tension at the fairlead is measured using a load cell and a dynamometer, and the motion of a part of the line is recorded using low-cost submerged cameras. Similarly to previous experiments, the fairlead tensions increase with higher amplitudes and lower periods, and a clear pattern in the motions of the line at different depths is found. The dissipated energy and the fairlead tension is also increased by the addition of the clumped weight, and the variation of this energy with its position along the line is monitored. The presence of clumped weights is also implemented into a finite element numerical code, previously validated without clumped weights, where all the previous experiments with clumped weights are replicated with remarkable accuracy. This double experimental and computational approach to the problem provides an important dataset for numerical code validations and opens future discussions about the impact of clumped weights on floating platforms

Experimental and Numerical Study of the Influence of Clumped Weights on a Scaled Mooring Line

Recently, several experimental and numerical studies have underlined the advantages of adding clumped weights at discrete positions of mooring lines. To confirm the influence of these weights, an experimental study was performed for a 1:30 scale model of a mooring line. In this study, the clumped weight is modeled as a scaled disc placed at different positions along the mooring line. The series of experiments has been carried out at the CEHIPAR towing tank using a submerged studless chain both with and without clumped weights. The experiments consist of the excitation of the suspension point with horizontal periodic motions using different amplitudes and periods, where the mooring line’s tension at the fairlead is measured using a load cell and a dynamometer, and the motion of a part of the line is recorded using low-cost submerged cameras. Similarly to previous experiments, the fairlead tensions increase with higher amplitudes and lower periods, and a clear pattern in the motions of the line at different depths is found. The dissipated energy and the fairlead tension is also increased by the addition of the clumped weight, and the variation of this energy with its position along the line is monitored. The presence of clumped weights is also implemented into a finite element numerical code, previously validated without clumped weights, where all the previous experiments with clumped weights are replicated with remarkable accuracy. This double experimental and computational approach to the problem provides an important dataset for numerical code validations and opens future discussions about the impact of clumped weights on floating platforms