Calculate the lift, drag and moment coefficient about quarter chord per unit span of an airfoil which is at an angle of attack of {7\, ^ \circ } with a flow velocity of 40\, m/s at standard sea level conditions. The airfoil has a chord length of 1\, m.
Calculate the lift, drag and moment coefficient about quarter chord per unit span of an airfoil which is at an angle of attack of {7\, ^ \circ } with a flow velocity of 40\, m/s at standard sea level conditions. The airfoil has a chord length of 1\, m.
[For this airfoil; {c_l} = 0.85\,,{c_{{m_{c/4}}}} =\, – 0.028,\,{c_d} = 0.075]
The dynamic pressure for the airfoil is
{q_\infty } = \frac{1}{2}{\rho _\infty }V_\infty ^2 = \frac{1}{2} \times 1.225 \times {\left( {40} \right)^2} = 980N/{m^2}
Area per unit span, S = 1 \times (c) = 1 \times 1 = 1
Therefore, lift per unit span,
L = {q_\infty }S{c_l} = 980 \times 1 \times 0.85 = 833\,N
Drag per unit span,
D = {q_\infty }S{c_d} = 982 \times 1 \times 0.075 = 73.5\,N
Moment about the quarter chord per unit span,
{M_{c/4}} = {q_\infty }Sc{c_{{m_{c/4}}}} = 980 \times 1 \times 1 \times \left( { – 0.028} \right) = – 27.44Nm
