Current simulation with Software in the Loop for floating offshore wind turbines

The presence of current is an added source of hydrodynamic loading on the platforms of Floating Offshore Wind Turbines (FOWT). Not only will current add viscous loading on the platform and moorings of FOWTs, but it will also affect wave loadings due to the alteration of wave shapes caused by wave-current interactions. Although the effects of current on platform response, mooring tensions and fatigue life have been numerically investigated, they are mostly neglected during scale model experiments for FOWTs. This paper proposes a novel method to simulate current loading and wave-current interactions during scale model tests by using a dynamic winch which is controlled using a Software in the Loop (SIL) approach. The winch is used in combination with a Multi-Propeller Actuator (MPA), for combined wave/wind/current testing in laboratory basins. The proposed current simulation method has lower costs and is more versatile than traditional physical current generation in a basin, as it allows for a wider range of test conditions and can be applied in any wave basin. A description of the experimental procedure is provided along with numerical validation using both AQWA and FAST. Results show that the winch actuator is capable of reliably emulating the drag force exerted by a current on the platform over a range of test conditions.