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

Abstract

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.

Keywords

• mooring line
• clump weights
• hybrid mooring system
• experiments
• floating offshore wind turbines