what is the angle of attack?

Consider an NACA $$2412$$ airfoil with a $$2\;m$$ chord in an airstream with a velocity of $$50\; m/s$$ at standard sea level conditions. If the lift per unit span is  $$1353\; N$$, what is the angle of attack?

Asked on 8th November 2019 in
We need to find here the angle of attack.Lift per unit span is ${L}’=\frac{1}{2}\rho _{\infty}V_{\infty}^{2}sc_{l}$
$q_{\infty}=\frac{1}{2}\rho _{\infty}V_{\infty}^{2}=\frac{1}{2}\times1.23\times50^{2}=1538\;N/m^{2}$
$c_{l}=\frac{{L}’}{q_{\infty}s}=\frac{1353}{1538\times2}=0.44$
For NACA $$2412$$ airfoil coefficient of lift of $$0.44$$ is at $$2$$ degrees angle of attack.