For one wind turbine blade section from $r/R = 0.45$ to $r/R = 0.55$ (centered on $r/R = 0.50$), find the
following:
a) $\phi$ (angle of relative wind), $\theta_p$ (section pitch), $\theta_r$ (twist angle), and $c$ (chord) for an ideal
blade (assume $C_d = 0$, $a' = 0$). Assume $\lambda = 7$, $B = 3$, $R = 5$ m, and $C_l = 1.0$ and the minimum
$C_d/C_l$ occurs at $\alpha = 7$.
b) Assume that $C_d/C_l$ actually equals 0.02 for the above blade section and that the free stream
wind speed, $U$, equals 10 m/s. Find $U_{rel}$, $dF_{L1}$, $dF_{D1}$, $dF_{M1}$, $dF_{T1}$, $dQ_1$ for the blade section.
Consider that the wind velocity is indeed slowed down at the rotor. Use $a = 1/3$, $a' = 0$. Assume
the air density is 1.24 kg/m³ (20° C).
