Aerofoil Geometry

LIFT

Following the principle of continuity, the flow leaving the leading edge must reach the trailing edge simultaneously.

This requires the airflow on the upper surface to travel faster due to the surface curvature.

Following Bernoulli’s Principle, this means that the static pressure on the lower surface is greater than the static pressure on the upper surface.

Hence a pressure gradient is present and lift is produced.

Creating a Pressure Gradient

A pressure difference can be achieved by:

•  Designing a cambered aerofoil.
• Increasing angle of attack.

Angle of Attack

The angle between the airflow and chord line.

Increased curvature on the upper surface induces a greater difference in static pressure.

AOA can only be increased to a certain extent. After this point, flow energy is not sufficient to remain attached to the surface, and lift is no longer produced. This is called a stall.

CAMBER

Camber line is defined as the points between the upper surface and lower surface.

Symmetric aerofoil is one where the aerofoil design is not cambered