Experimental Comparison of an Annular Floating Offshore Wind Turbine Hull Against Past Model Test Data

Floating offshore wind turbine (FOWT) hull technologies are evolving rapidly with many technically viable designs. However, a commercially dominant architecture has yet to emerge. Early hull designs including semisubmersible, spar, and tension leg platforms were largely derived from offshore oil and gas technologies, but recent developments in the commercial application and optimization of FOWTs have resulted in a number of unique, FOWT-specific hull configurations. One hull design of interest includes the application of a moonpool to aid in mitigating platform motion in the presence of waves. A version of this annular hull has been deployed in France and Japan. In this paper, a 6-MW version of an annular hull is studied through experimental model testing and numerical analysis. The primary portion of this work involves testing a 1/100th-scale model in the Harold Alfond Wind Wave Ocean Engineering Laboratory at the University of Maine. A secondary component of this work investigates the capability of ANSYS aqwa, a typical commercial hydrodynamic software, to recreate the wave-induced motion of a FOWT hull containing a moonpool. An additional secondary component of this study compares the wave-only performance of the annular hull to experimental data obtained for the DeepCwind semisubmersible, spar, and tension leg platform to provide context for the measured response. The results obtained show that ANSYS aqwa can adequately predict the gross response of the annular hull motion and that the moonpool design tested often exhibits greater motion than the systems tested during the DeepCwind campaign.