Under the Froude-scale model test environment with the scale of 1/54th, the strong Reynolds scale effects obstructs the model rotor capturing enough thrust. One effective solution is redesigning a performance matched blade to replace geometry similar blade. In this paper, the MATLAB's pattern search optimization toolbox and NREL's aerodynamic software AeroDyn V15 had been compiled together to design a blade for a 6MW floating offshore wind turbine (FOWT). And the redesigned blade was analyzed by CFD method, which had shown a reasonable agreement with the performance of prototype blade. Finally, a pitch performance mapping of the designed blade was captured preparing for future basin model test.
As a promising renewable and sustainable energy, wind energy has been made great use during the past decades. Many researching projects, especially for onshore wind turbines, had been done trying to improve its performance. And great major technology achievements have been made for onshore wind turbine, such as power capturing, noise control, which technologies are basically grasped now. Relatively, as it is known, offshore wind turbines in deep sea, would enjoy a more steady wind field without noise or visually disruption problem, which has become a promising development direction in the future wind turbine market. However, as a matter of coupled blades' aerodynamic and hydrodynamic of platform, the floating offshore wind turbines are much more challenged in technology, comparing with the onshore wind turbine or turbines erecting on a fixed platform in shallow sea. A few related researching projects have been carrying out but there many technical obstacles still remain. When a new FOWT conception was put forward, taking a high quality basin model test would be necessary to measure its performance. As a reliable and economic method, a basin model test will capture valuable data which define the aerodynamic and hydrodynamic performance of prototype wind turbine. Specifically, conducting basin model test in a Froude environment for FOWT, whether the model blade reaches admire Froude-scaled thrust or not plays an important role when detecting response of the floating platform. However, under Froude similar environment, the rotor which is similar to prototype rotor's geometry, had shown much lower thrust at a range of working condition, and this kind of deficient had caused huge challenges to basin model test (Coulling, Goupee, Robertson., Jonkman, & Dagher, 2013). This phenomenon attributes to the immense Reynolds dissimilitude between the full scale and model scale blade turbine. More directly, for a 6MW FOWT with the scale ratio 1/54th of this paper presented, the full scale blade turbine working in a rated condition getting a Reynolds number (Re) in a range of 106~107, in contrast, the model scale blade turbine works with a Re range in 104 or lower to 103 near root area.
