**3.1 Geometric model of turbine**

For the assessment of trailing edge bluntness noise from horizontal axis wind turbine rotors, a geometric model for the blade has been developed using NuMAD software [18]. The software allows user to input the aerofoil data at every span wise location of the blade. **Table 1** shows the turbine design parameters along with orientation of rotor into wind.

**Figure 2** shows the isometric (3D) model of the 38 m blade for the 2 MW wind turbine used for analyzing the trailing edge bluntness noise. Towards the inboard region, the airfoils have high thickness to chord ratio with at least 18% t/c as well as high camber. In the present study NACA 6320 airfoil data have been used with a


#### **Table 1.**

*Turbine parameters for 2 MW machine.*

### **Figure 2.**

*Isometric (3D) model of wind turbine developed using NuMAD software showing the airfoil sections used near the blade root, mid-span, and tip of the blade [18].*

**Figure 3.** *Geometric properties shown along the normalized blade span for a wind turbine blade having a length of 38 m.*

trailing edge slope angle of 14<sup>o</sup> . In the mid span region, the airfoils have moderate thickness to chord ratio. The geometric properties of the blade are depicted in **Figure 3**. It is evident that chord length and twist remain constant for root section which connects the blade to the rotor hub.

*Trailing Edge Bluntness Noise Characterization for Horizontal Axis Wind Turbines [HAWT]… DOI: http://dx.doi.org/10.5772/intechopen.99880*

#### **Figure 4.** *Illustration of microphone position surrounding the source located in Centre as well as the microphone measurement distances and position according to IEC 61400–11 standards with respect to source.*
