Question

In thin airfoil theory the lift curve slope is usually considered as

• A. \(0.10\) per degree
• B. \(0.11\) per degree
• C. \(0.09\) per degree
• D. \(2\pi\) radians

Hint:

Lift curve slope = change in lift coefficient with angle of attack.

Answer 1

The Correct Option is B

In thin airfoil theory, the lift curve slope is a key parameter that describes how the lift coefficient (\(C_L\)) of an airfoil changes with the angle of attack (\(\alpha\)). The lift curve slope is defined as the change in lift coefficient per unit change in angle of attack. For thin airfoils, the lift curve slope is approximately constant over a range of small angles of attack.

The theoretical lift curve slope for a thin symmetrical airfoil in incompressible flow is given as \(2\pi\) per radian. To calculate the slope per degree, we use the conversion factor between radians and degrees:

\[2\pi \text{ radians} = 360 \text{ degrees}\]

Thereby, the lift curve slope in terms of degrees can be calculated using:

Slope per degree = \(\frac{2\pi}{360}\)

Evaluating the formula:

\[\frac{2\pi}{360} = \frac{2 \times 3.14159}{360} \approx 0.11 \text{ per degree}\]

This calculation shows that the lift curve slope is approximately \(0.11\) per degree in the context of thin airfoil theory. Therefore, the correct answer is:

\(0.11\) per degree.