How much is alpha induced angle?

Question

I know that alpha induced rise with increasing AoA but how much is alpha induced in reality ,are we talking about 1-2 degrees or more?

Answer 1

The induced angle primarily depends upon the following:

• Coefficient of lift
• Aspect Ratio (AR)
• The correction factor $\tau$ (needs to be accounted for if the wing platform is not an ellipse. If the wing platform is an ellipse, then $\tau=0$)

All three are related the with the following equation: $$\alpha_i[\text{rad}]=\frac{C_z}{\pi AR}(1+\tau)$$

The table below provides the values of $\tau$ for a rectangular wing.

You can use these values and NACA Report 824 to calculate the actual induced angle of attack for a rectangular wing for any possible airfoil.

For instance, using $\text{NACA} ~65_1-412$ airfoil at $\alpha_{\text{geometric}}=8^{\circ}$ and $AR=9$ it follows that $\alpha_i=0.05~\text{rad}\approx 2.86^{\circ}$.

It varies greatly in relation to the angle of attack, as low as $1^{\circ}$ in high-speed flight with low angle of attack and as high as $3^{\circ}-4^{\circ}$ at low-speed flight for a rectangular wing aircraft.