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In ocean environments, floating wind turbines are subject to both breaking waves and directional waves. While the response is often modelled through radiation-diffraction theory, the effects of higher-order wave loads are hereby limited to second order, and the damping often needs calibration against model tests. Better accuracy and full coverage of nonlinearity can be achieved through CFD. However, there is a limited robust Open Source CFD based six degrees of freedom (6-DOF) rigid body solvers, that can both generate different types of waves and also accurately simulate floating foundation motions. FloatStepper, a recent OpenFOAM-based rigid body motion algorithm, effectively addresses these differences, making it a good alternative to conventional body motion solvers. Its reliability and accuracy have been demonstrated in several benchmark cases, including single-phase and two-phase flows. The present study conducts a comprehensive examination the motion responses and mooring line tensions to unidirectional and multi-directional waves for a design variant of Stiesdal Offshore's TetraSub floating foundation, using the FloatStepper algorithm. In particular, three categories of waves are investigated: 1) regular waves 2) unidirectional irregular and 3) multi-directional (3D) focusing waves. The numerical results are validated through comparison with experimental data from the 2023 test campaign of the Danish FloatLab project. The study contributes to the efficient use and validation of this robust CFD solver. It further extends the understanding of the multi-directional waves and wave-structure interaction for floating wind turbines, identifying potential limitations and areas for refinement in the modelling of this complex dynamics in CFD.
Aliyar et al. (Sun,) studied this question.