Effect of Airfoil Concavity on Wind Turbine Blade Performances

Figure 12

Differences between sound pressure levels of the original and modified blades. represents the wind speed; f₁ is the blade rotating fundamental frequency; f₂, f₃, and f₄ are two, three, and four times the value of f₁. (a)  = 6 m/s. (b)  = 7 m/s. (c)  = 8 m/s.

(a)

(b)

(c)