NREL is a national laboratory of the U.S. Department of Energy Office of Energy Efficiency & Renewable Energy Operated by the Alliance for Sustainable Energy, LLC This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications. Contract No. DE-AC36-08GO28308 Comparison of Hydrodynamic Load Predictions Between Engineering Models and Computational Fluid Dynamics for the OC4-DeepCwind Semi- Submersible Preprint Maija A. Benitz, David P. Schmidt, Matthew A. Lackner, and Gordon M. Stewart University of Massachusetts Jason Jonkman and Amy Robertson National Renewable Energy Laboratory Presented at the ASME 2014 33 rd International Conference on Ocean, Offshore and Arctic Engineering (OMAE2014) San Francisco, California June 8–13, 2014 Conference Paper NREL/CP-5000-61157 September 2014