Effect of Airfoil Concavity on Wind Turbine Blade Performances

Table 1

Modal test results.

Blade	f1 (Hz)	f2 (Hz)	ζ1 (%)	ζ2 (%)
Original	27.4	60.7	7.6	4.2
Modified	28.3	62.4	13.8	6.5
φ (%)	3.3	2.8	81.6	54.8

f₁ and f₂ represent the natural frequencies of the first- and second-order vibrations of the blade, ζ₁ and ζ₂ represent the corresponding damping ratios, and φ represents the relative increase in the same parameter.