Development and validation of a tightly coupled CFD/6-DOF solver for simulating floating offshore wind turbine platforms

• Simulations of offshore floating wind turbine dynamics typically utilize reduced order models which can be inaccurate for large amplitude motion.
• An open-source CFD/6-DOF solver is developed using OpenFOAM for simulation of offshore flating wind turbines.
• The solver tightly couples the fluid and 6-DOF equations of motion to eliminate the artificial added mass instability.
• Validation of the tightly coupled CFD/6-DOF solver is carried out on a benchmark case.
• The solver is then used in simulations of an offshore platform and compared with FAST.

Simulations of offshore floating wind turbine platform dynamics typically utilize engineering tools that include simplified modeling assumptions. In this study, an open-source CFD/6-DOF solver is developed using OpenFOAM for high-fidelity simulation of offshore floating wind turbine platforms. The solver tightly couples the fluid and 6-DOF equations of motion using subiterations and dynamic relaxation to eliminate the artificial added mass instability. Validation of the tightly coupled CFD/6-DOF solver is carried out on a benchmark case of the free decay of a heaving cylinder. The solver is then used in simulations of the DeepCwind semisubmersible platform and compared with FAST, a NREL engineering tool. The CFD/6-DOF solver and FAST are compared in four cases including both rotational and translational motion. Overall, the results demonstrate that the tightly coupled solver compares well with FAST. The tightly coupled CFD/6-DOF solver represents an advance in modeling of offshore wind turbine platform dynamics using open-source software that may be used for wind turbine research, design, and analysis.