Airfoil
Definition and Overview
An Airfoil is a shape designed to obtain a desirable reaction from the air through which it moves. Airfoils are primarily used in the design of wings for aircraft, propeller blades, wind turbine blades, and other applications related to aeronautics and aerodynamics. The term "airfoil" is often used interchangeably with "aerofoil" in scientific and engineering literature.
Design and Characteristics
Airfoils are designed to generate lift when moving through the air, while minimizing drag. The shape of an airfoil plays a crucial role in its performance, with the upper surface typically being more curved than the lower surface. This difference in curvature creates a pressure differential when air flows over the airfoil, resulting in lift.
The design of an airfoil involves several key parameters, including the chord line, camber line, leading edge, trailing edge, and angle of attack. The chord line is the straight line connecting the leading and trailing edges of the airfoil, while the camber line is the curve that best fits the shape of the airfoil. The leading edge is the point at the front of the airfoil with the smallest radius, and the trailing edge is the rear-most point. The angle of attack is the angle between the chord line and the oncoming airflow.
Types of Airfoils
There are several types of airfoils, each with its own unique characteristics and applications. These include symmetrical airfoils, cambered airfoils, and supercritical airfoils.
Symmetrical airfoils have the same shape on both the upper and lower surfaces, resulting in zero camber. These airfoils are often used in aerobatic aircraft due to their predictable characteristics at high angles of attack.
Cambered airfoils have a different shape on the upper and lower surfaces, resulting in a positive camber. These airfoils generate lift at zero angle of attack and are commonly used in general aviation and commercial aircraft.
Supercritical airfoils are a type of cambered airfoil designed to delay the onset of wave drag in the transonic speed range. They are used in high-speed commercial aircraft and military jets.
Applications
Airfoils are used in a wide range of applications, from aircraft and helicopters to wind turbines and propellers. In aircraft, airfoils are used in the design of wings, tailplanes, and helicopter rotor blades. In wind turbines, airfoils are used in the design of the turbine blades to extract energy from the wind. In propellers, airfoils are used to generate thrust by creating a pressure differential between the front and back surfaces of the propeller blades.