Turning motion of multi-connection cross-flow vertical axis offshore wind turbines tension moored at a single point

This version of the article has been accepted for publication, after peer review (when applicable) and is subject to Springer Nature’s AM terms of use, but is not the Version of Record and does not reflect post-acceptance improvements, or any corrections. The Version of Record is available online at: https://doi.org/10.1007/s40722-023-00281-2

This study proposes a multi-connection cross-flow vertical axis wind turbine, an innovative device to supply electric power in aquaculture farms. The device is a new type floating offshore wind turbine consisting of two independent wind turbine floats and a mooring float set in a straight line. A single-point mooring system with tension is utilized at the mooring float, which allows the wind turbine floats to turn around the moored point. However, there are various challenges to this new concept for its practical application mainly related to turning motion about the moored point. Therefore, the focus of this study is to understand the turning mechanism of the proposed FOWT through dedicated water tank experiments and numerical simulations. As a concept demonstration, two cross-flow wind turbines were mounted on the wind turbine floats and turning motion characteristics about the moored point were observed. A prototype model was built with a model scale of 1/36 using Froude scaling assuming rough weather conditions at the aquaculture farm. Wind speed of 35m/s, wave height of 0.75m, and wave period of 5–7.5s are the assumed environmental conditions in the actual model. Free yawing tests were conducted in only-wind, only-wave and combined wind–wave conditions. Further, a numerical simulation considering the wind loads acting on the turbines is developed. It is found that the wind turbine floats turn to a position where the wind loads acting on the left and right sides of the moored point are balanced. The numerical simulation reproduced the turning motion within an error of 10.