Comparison of Real-Time Hybrid Model Testing of a Braceless Semi-Submersible Wind Turbine and Numerical Simulations

In this paper, integrated analyses performed in SIMA are compared against experimental results obtained using real-time hybrid model testing (ReaTHM^®) carried out in the ocean basin facilities of MARINTEK in October 2015. The experimental data is from a 1:30 scaled model of a semi-submersible wind turbine. Coupled aero-hydro-servo-elastic simulations are performed in MARINTEK’s SIMA software. The present work extends previous results from Berthelsen et al. [1] by including a blade element/momentum (BEM) model for the rotor forces in SIMA and comparing the coupled responses of the system to the experimental results. The previously presented hydrodynamic model is also further developed, and the importance of second order loads (and applicability of approximate methods for their calculations) is examined. Low-frequency hydrodynamic excitation and damping are seen to be important, but these loads include a combination of viscous and potential forces. For the selected concept, the second order potential flow forces have limited effects on the responses.