2.2.3. Calculation Method for the CFD Simulation

Considering that the subsequent topology optimization of wind turbine blade is a static solution question, the moving reference frame (MRF) method was adopted in this work. Specifically, the rotation speed of the wind turbine is attached to the rotation domain, and the flow fluxes originated from the stationary domain can be translated by the interface. Compared to the non-constant slip grid method, the MRF method is a constant calculation method, which is simpler, faster with less computation time to produce acceptable results in a short time. The method has been used in CFD simulations of static wind turbine blade [37,38].

#### *2.3. Finite Element Model of Reference Composite Wind Turbine Blade*

#### 2.3.1. Mechanical Properties of Composite Materials of Wind Turbine Blades

Glass fiber reinforced resin unidirectional composites were used as the skin material of blade in this work. The mechanical properties and corresponding allowable values of composites can be found in Table 1.


**Table 1.** Mechanical properties and allowable values.

Note: "*TS*", "*CS*" and "*GS*" indicate the tension, compression and shear strength.

#### 2.3.2. Finite Element Model of Wind Turbine Blade

As the wind turbine blade has a complex geometric configuration, the ANSYS Meshing was used to generate tetrahedral elements for the internal room of the blade in this work. Furthermore, to weaken the influence of mesh dependence on the blade, the mesh size was chosen as 0.07 m. Finally, the total number of elements and nodes were 4.85 million and 6.69 million. The corresponding model can be found in Figure S2, SI.
