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Limited by scaling effects, the physical model tests of FOWTs (floating offshore wind turbines) cannot simulate the aerodynamic loads on rotors correctly. To solve this problem, the real-time hybrid model tests in wind tunnels were developed and provided a feasible solution for the aerodynamic simulation. To perform the wind tunnel tests, the design of aerodynamic equivalent rotor models is most critical. In this study, an innovative methodology of aerodynamic equivalent design for the wind turbine rotors is developed based on GA (genetic algorithm). The NREL (National Renewable Energy Laboratory) 5 MW and DTU (Technical University of Denmark) 10 MW rotors are employed for the case studies to validate the proposed methodology. According to the results, the model-scale aerodynamic thrust performance can be accurately matched with the prototype in the entire region between cut-in and cut-out wind speeds, which allows the rotor model to provide correct thrust at different wind speeds. The variance of the aerodynamic torque with the wind speeds for the developed model is also in good agreement with the prototype, which could be beneficial for the design of the model-scale active pitch control strategy. Moreover, the applicability of the fitness functions of GA is discussed. [ABSTRACT FROM AUTHOR]

The nonlinear dynamic behaviour of steep wave riser (SWR) subjected to the top harmonic motions considering the effect of the internal flow is numerically investigated using a three-dimensional (3D) time-domain finite element method (FEM) based on the slender flexible rod theory. In this numerical model, the riser which satisfies geometric nonlinearity is divided into three segments: decline segment, buoyancy segment and hang-off segment and the effect of the internal flow is also incorporated into motion equation using plug flow. A Newmark-β integral method is applied to update the dynamic responses at each time step. The published results for the static/dynamic performance of the steel flexible riser are used to validate the present numerical method. Numerical simulations are conducted to investigate the dependence of the tension, displacement and bending moment on the design parameters. The top motion amplitude/period, buoyancy length and internal flow density/velocity/top pressure are discussed respectively. [ABSTRACT FROM AUTHOR]