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

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.

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