Prediction of an advanced spar’s horizontal motions, validated by full scale observation data

Abstract

As the offshore wind industry moves into deeper waters, the number of different floating wind platform concepts continues to expand. Accurately predicting the motion characteristics of these novel platforms is crucial to the safe and economic conversion of wind energy into electricity. A challenge in the currently used numerical simulation methods involves successfully predicting the slow drift motions and damping, especially in complex realistic environmental conditions which include multi-directional spectral waves, current and wind loading. Of most uncertainty to these predictions is determining the low frequency viscous damping which dominates the resonant surge and sway motions. In this paper, full-scale motion observations of the Fukushima FORWARD’s floating wind substation are used to determine the platforms viscous drag forces. These drag coefficients are used in a combined potential flow and Morison’s equation model to capture the observed behaviour. This validated numerical model is then used to describe the required fidelity of mooring line models, in order to aid platform developers in the early stages of design.