In Froude-scaled model tests of floating wind turbines, if the Reynolds number is higher than the critical Reynolds number, the scale effect can be neglected. In this paper, seven scale factors (1:100, 1:50, 1:30, 1:20, 1:15, 1:10 and 1:3) were used to calculate the rotor thrust coefficients of the NREL offshore 5-MW baseline wind turbine model blades. XFOIL software was used to analyze the lift and drag coefficient curves of the six airfoils. The thrust coefficients were obtained and compared with those of the prototype applying the Blade Element Momentum Theory. It can be concluded that the critical Reynolds number is approximately 2×105 (with a scale factor of 1:15). Lower Reynolds number model blades will show unfavorable aerodynamic performance in the model test.

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