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In marine applications, the scaled wind turbine model (SWTM) based aerodynamic testing apparatus is regarded as one of the most effective approaches to predict the aerodynamic performance of offshore floating wind turbines (OFWTs). To fully disclose the aerodynamics of OFWTs, such kind of apparatus should meet two design requirements: 1) accurate representation of the aerodynamic characteristics of reference wind turbines and 2) reasonable reproduction of the environmental factors from real-world wind-wave-coupled field. Baring with these considerations, the authors propose a cost-effective SWTM based aerodynamic testing apparatus, which consists of an innovative SWTM, a wind-wave simulator (WWS), and a data acquisition and analyses system. The proposed SWTM is featured by a double-deck tower, which satisfies the requirements of similarity in geometry, stiffness, and mass, and a set of redesigned blades. The proposed WWS is capable of simulating both the time-varying inflow wind and the wave-induced platform motions through a wind field generator and a motion simulator. Based on the developed apparatus, a series of aerodynamic tests are conducted to validate the effectiveness of the apparatus design. In addition, the coupling effects of inflow wind and platform motions on aerodynamics of OFWT are further revealed through experimental tests.

In the natural marine environment, offshore floating wind turbines (OFWTs) inevitably experience yawed inflow conditions, which will make their aerodynamics more complicated than those experiencing uniform inflow conditions and difficult to understand. In the present study, the thrust characteristics of a wake-influenced OFWT under dynamic, static, and coupled yawed inflow conditions are investigated thoroughly. Analytical characterizations of yawed inflow and upstream wake are integrated into the blade element momentum (BEM) method to achieve the investigation. Based on this method, simulations by the FAST code have been conducted, and the results are analyzed. It is shown that the three inflow conditions have considerable influences on the thrust coefficient of the wind rotor or the normal force at the blade section, especially in the wake case where the downstream OFWT is located at a specific offset from the central line of a single upstream wake. In order to validate the analyses of simulation results, experimental tests by a set of dedicated apparatus are conducted. The comparison results are good, proving the reliability of simulation results. This work can provide some theoretical contributions to the aerodynamic design and control of OFWTs.

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The Froude-scaled offshore floating wind turbine model is inevitably affected by the Reynolds number effect, making the model unable to correctly reproduce the thrust performance of the reference wind turbine (RWT). To solve this problem, an Xfoil-AirfoilPrep-Matlab (XAM) system and a wide tip speed ratio search method (WTSM) are proposed to design a wide tip speed ratio (TSR) thrust-match model blade. The XAM system is utilized to select the best airfoil for WTSM by calculating the lift and drag coefficients of several airfoils. The WTSM is utilized to optimize the blade chord and twist. It formalizes the blade chord and twist by polynomials and then optimizes the polynomial coefficients. The thrust coefficients construct the optimization object at different TSRs. For validating the effect of the redesigned blade, the thrust performance is compared to that of the RWT blade. In addition, the thrust performance of redesigned blade at different pitch angles is also calculated and compared to those of the RWT blade. Results show that the thrust performance of redesigned blade matches well with that of the RWT blade at 0 pitch angle, and it can also match the variations of that of the RWT blade at the other pitch angles well.