by Kat Griffin Kat Griffin

What is an airfoil and what’s its purpose?

angle of attack | airfoil applications and its purpose

An airfoil is a curved surface, such as a wing, designed to generate lift when air flows over it. Its shape and curvature are optimized to produce the desired lift-to-drag ratio, which is critical for the performance of aircraft and other applications.


Airfoil Applications and Its Purpose

Airfoils are used in a wide range of applications, from aircraft wings to wind turbines. By generating lift, they enable aircraft to take off and stay in the air. In addition, airfoils play a crucial role in the efficiency and performance of wind turbines.

The flow of air over the top of the airfoil is faster than the flow underneath it, which creates a difference in pressure between the two surfaces. This difference in pressure generates a lifting force that acts perpendicular to the direction of the airflow, allowing the airfoil to lift.

The shape of the airfoil is crucial to its performance. The curvature of the airfoil, known as its camber, is designed to create a pressure difference that produces lift. The angle at which the airfoil is positioned relative to the airflow, known as the angle of attack, also affects its lift and drag characteristics.


Airfoil Design

There is no one optimal airfoil design that works for all aircraft, and the choice of airfoil design depends on a variety of factors such as the intended purpose of the aircraft, the desired performance characteristics, and the operating conditions.

For example, an airfoil designed for a high-speed fighter jet may have a different shape and characteristics compared to an airfoil designed for a small personal aircraft or a glider. Factors such as the aircraft’s weight, speed, altitude, and maneuverability all play a role in determining the most suitable airfoil design.

Therefore, airfoil design is a complex and iterative process that involves a combination of theoretical analysis, wind tunnel testing, and computer simulations to optimize the airfoil’s performance for the specific application.


Airfoil Design Terminology

  • Chord Line: A theoretical straight line between the leading and trailing edges, the airfoil’s front-most and rear edges, respectively.
  • Mean Camber Line: The centerline between the upper and lower surfaces. Camber describes how curved an airfoil is.
  • Upper Surface Camber: The curve of the top of the airfoil that is typically more pronounced than the lower surface.
  • Lower Surface Camber: The curve of the bottom of the airfoil.
  • Angle of Attack: The angle between the chord line and flow direction.
  • Relative Wind: Airflow relative to an airfoil created by movement of the airfoil.
  • Thickness: The distance between the upper and lower surfaces, measured perpendicular to the chord line.
  • Camber Ratio: The ratio of the maximum camber to the chord length.
  • Leading Edge: The forward-most edge of the airfoil.
  • Trailing Edge: The rear-most edge of the airfoil.
  • Stall: The condition where the airfoil’s angle of attack is too high. This will cause a loss of lift and an increase in drag.
  • Lift Coefficient: A dimensionless quantity that relates the lift generated by an airfoil to its size, speed, and angle of attack.
  • Drag Coefficient: A dimensionless quantity that relates the drag force generated by an airfoil to its size, speed, and angle of attack.
  • Boundary Layer: A thin layer of air that flows along the surface of the airfoil. This can affect the airfoil’s performance and efficiency.