Airfoil

An airfoil (American English) or aerofoil (British English) is a special shape that helps objects fly or move smoothly through the air. Wings on airplanes, sails on boats, and the blades of propellers are all examples of airfoils. These shapes are designed to create more lift than drag when they move through a fluid like air or water.

When an airfoil moves through the air at the right angle, it pushes the air aside. This creates a force called an aerodynamic force (aerodynamic force), which has two parts: lift that pushes the object up and drag that slows it down. The amount of lift depends mostly on the angle of attack (angle of attack), which is the angle between the airfoil and the oncoming air.

Airfoils come in different shapes for different speeds. Those used for slower, or subsonic flight (subsonic flight), have a rounded front called the leading edge (leading edge). For very fast, or supersonic flight (supersonic flight), the airfoil is usually thinner. All airfoils end in a sharp point called the trailing edge (trailing edge). The way an airfoil moves air creates areas of lower pressure above it, which helps it generate lift.

Overview

The wings and stabilizers of fixed-wing aircraft, as well as helicopter rotor blades, are built with airfoil-shaped cross sections. Airfoils are also found in propellers, fans, compressors and turbines. Sails are airfoils, and the underwater surfaces of sailboats, such as the centerboard, rudder, and keel, work in a similar way. Airfoils help create lift and reduce drag, making flight and movement through water more efficient.

Airfoils are specially shaped to generate more lift than drag compared to flat surfaces. They are used in many designs, from aircraft wings to wind turbine blades. Different types of airfoils are used for different purposes, such as flying upside down or moving faster than the speed of sound. Modern wings often have special devices like flaps to help them fly more efficiently.

Airfoil terminology

An airfoil is a special shape that helps objects like wings and sails move through air or water smoothly. It has two main sides: the suction surface on top and the pressure surface on the bottom. The difference in pressure between these two sides helps create lift, which is what makes planes fly.

Key parts of an airfoil include the leading edge, where the air first touches the wing, and the trailing edge, where the air leaves. The straight line connecting these two points is called the chord line, and its length is known as the chord. Other important features include the camber (how curved the top is) and the thickness (how fat the wing is). These shapes and measurements help engineers design wings that work best for different kinds of aircraft.

Thin airfoil theory

Thin airfoil theory is a simple way to understand how wings and other shapes can create lift. It was created by a German mathematician named Max Munk and improved by a British scientist named Hermann Glauert in the 1920s. This theory looks at air moving around a very thin wing as if it were a flat, two-dimensional shape.

This theory helps explain some important facts about airfoils, like how the center of pressure and aerodynamic center are positioned on a symmetric wing, and how lift changes with the angle the wing makes with the airflow. It also gives a simple formula to calculate lift based on the angle of attack, which is the angle between the wing and the oncoming air. However, it does not account for what happens when the airflow separates from the wing, known as stall, which usually occurs at higher angles.