RE: Calculate the lift and moment about the quarter chord (per unit span) for this airfoil.
Consider the data for the NACA 2412 airfoil. Calculate the lift and moment about the quarter chord (per unit span) for this airfoil when the angle of attack is 4^{\circ} and the freestream is at standard sea level conditions with a velocity of 50 ft/s. The chord of the airfoil is 2 ft.
Dynamic pressure q_{\infty}=\frac{1}{2}\rho _{\infty}V_{\infty}^{2}=\frac{1}{2}\times0.002377\times50^{2}=2.97\;lb/ft^{2}.Fo r NACA 2412 airfoil coefficient of lift c_{l}=0.64,c_{m,c/4}=-0.036.
Lift per unit span {L}’=q_{\infty}sc_{l}=2.97\times2\times1\times0.64=3.80\;lb/span
Moment about the quarter chord {M}’=q_{\infty}scc_{m,c/4}=2.97\times2\times1\times2\times\left ( -0.36 \right ) \\=-0.428\;ft/lb per unit span.
