Comparison of Hydrodynamic Load Predictions Between Engineering Models and Computational Fluid Dynamics for the OC4-DeepCwind Semi-Submersible

Hydrodynamic loads on the platforms of floating offshore wind turbines are often predicted with computer-aided engineering tools that employ Morison's equation and/or potentialflow theory. This work compares results from one such tool, FAST, the National Renewable Energy Laboratory's wind turbine computer-aided engineering tool, and the high-fidelity computational fluid dynamics (CFD) package, OpenFOAM, for the OC4- DeepCwind semi-submersible analyzed in the International Energy Agency Wind Task 30 project. Load predictions from Hydro- Dyn, the offshore hydrodynamics module of FAST, are compared with results from OpenFOAM. HydroDyn uses a combination of Morison's equation and potential-flow theory to predict the hydrodynamic forces on the structure, at a small computational cost compared to CFD. The implications of the assumptions in Hydro- Dyn are evaluated based on this code-to-code comparison.