Numerical Modelling of Floating Wind Semi-Submersible (FWSS) Platform for 15 and 22 MW Offshore Wind Turbine

Abstract The objective of this paper is to introduce numerical modelling of a large (15 MW or more) Floating Wind Semi-Submersible (FWSS) platform design for in-place analysis. FWSS is a three-column Semi-Submersible design for offshore wind turbines, featuring three eccentrically positioned columns on separate pontoons enhancing stability within the same footprint. A fourth open column at the centre supporting the turbine serving dual purposes as a cable conduit for the wind turbine cables. The Floating Wind Semi-Submersible, with low draft and large airgap is designed for benign and extreme environment as well as shallow and deep-water applications. This paper discusses the development of various numerical models for global performance analysis of the FWSS. Aerodynamic and hydrodynamic coupled analyses are conducted numerically using OrcaFlex and ANSYS AQWA to simulate the behaviour of the FWSS under combined wind, wave, and current loads. The simulations evaluate global motion responses and performance of the FWSS in both operational and survival scenarios. The numerical studies are validated with advanced coupled cyber-physical model tests, which integrate physical simulation of hydrodynamic loads with real-time numerical computation of aerodynamic loads. The validation results indicate that, for the conditions considered, the coupled FWSS responses under combined wind, wave, and current loading can be reproduced though the combination of the hydrodynamic and aerodynamic models that were validated independently. Additionally, the study explores how the FWSS platform scales with increasing turbine size to 22 MW, offering insights into the design's adaptability for next-generation offshore wind applications.