Experimental-numerical model comparison of a dynamic power cable for a floating offshore wind turbine

Dynamic power cables for floating offshore wind turbines (FOWTs) are designed using global numerical modelling tools, to optimise cable configuration. The presented study is a comparison between a global numerical model and a scale physical model, of a dynamic power cable during an operational sea state and a 1-in-50-year storm. Ocean basin experiments were performed with a 1:70 scale model of a dynamic power cable, connected in a tethered wave configuration to a semi-submersible FOWT in water depth representing 70 m, in the COAST laboratory at the University of Plymouth. Measured values of the physical model were used in the numerical model, to enable a like-for-like comparison. Cable motions recorded are compared with the numerical model using trajectory plots, spectral analysis, curvature analysis and analysing acceleration peaks. The numerical model predicts cable motion response well for both tests, with small differences identified across both low frequency and wave frequency regions of response. Differences are also identified in acceleration peaks, with the numerical model predicting smaller peaks for several cable sections. It is shown that cable motion is significantly influenced by motion of the FOWT, but direct wave loading on the cable must also be modelled accurately to fully capture motion response.