Development of variable-fidelity FOWT digital twins in extreme sea environments: Part II – high-fidelity CFD analysis

In the coming years, more Floating Offshore Wind Turbines (FOWT) are projected to be installed beyond the continental shelf in the USA and worldwide. Accurate and reliable modeling of various environmental loadings and the resulting dynamic responses are crucial for the structural design, operation, and safety of FOWTs. To develop accurate and reliable FOWT design tools, a collaborative effort between academia (TAMU), industry (Technip Energies), and class society (ABS), supported by the Ocean Energy Safety Institute (OESI), has been undertaken. In this project, accurate and reliable digital twin (DT) models were developed based on high-fidelity CFD models and mid-fidelity potential-flow models. These DT models simulate the coupled dynamics of the floater-turbine-control-mooring system and were validated against 5MW OC3 semisubmersible model test results. The present study is presented in two separate papers. This paper, Part II, focuses on the development and validation of CFD-based high-fidelity DT model for a 15MW semi-submersible wind turbine model. In the high-fidelity coupled analysis methodology, aero-servo-elastic behaviors of the wind turbine blade and tower are simulated by OpenFAST, and the hydrodynamic loads on the floating platform and mooring system are simulated by Technip Energies' CFD-based numerical wave basin tool. The high-fidelity DT simulations were performed for various extreme environmental conditions, and the CFD results were used to calibrate the empirical coefficients of mid-fidelity tools. The development and the validation of mid-fidelity DT models are presented separately in another paper, Part I.