Sweep theory is an aeronautical engineering description of the behavior of airflow over a wing when the wing's leading edge encounters the airflow at an oblique angle. The development of sweep theory resulted in the swept wing design used by most modern jet aircraft, as this design performs more effectively at transonic and supersonic speeds. In its advanced form, sweep theory led to the experimental oblique wing concept. Aerospace engineering is the branch of engineering concerning aircraft, spacecraft and related topics. ... A Laughing Gull on the beach in Atlantic City. ... The swept wing of an airliner: British Midland Airbus A320-200 A swept-wing is a wing planform used on high-speed aircraft that spend a considerable portion of their flight time in the transonic. ... Transonic is an aeronautics term referring to a range of velocities just below and above the speed of sound. ... It has been suggested that hypersonic be merged into this article or section. ... Oblique wing The Oblique wing, Ames-Dryden-1 (1979), is another example of a variable geometry aircraft. ...

Overview

Sweep theory in general was a subject of development and investigation throughout the 1930s and 1940s, but the breakthrough mathemetical definition of sweep theory is generally credited to NACA's Robert T. Jones in 1945. Sweep theory builds on other wing lift theories. Lifting line theory describes lift generated by a straight wing (a wing inwhich the leading edge is perpendicular to the airflow). Weissinger theory describes the distribution of lift for a swept wing, but does not have the capability to include chordwise pressure distribution. There are other methods that do describe chordwise distributions, but they have other limitations. Jones' sweep theory provides a simple, comprehensive analysis of swept wing performance. NACA may mean: National Advisory Committee for Aeronautics National Association for Campus Activities [1] Network of Aquaculture Centres in Asia-Pacific, an industry association of shrimp farmers and other aquaculture industries. ... Bobby Jones can refer to different people: Bobby Jones: a golf player Bobby Jones: a baseball player Bobby Jones: a basketball player Bobby Jones: a gospel singer This is a disambiguation page — a navigational aid which lists other pages that might otherwise share the same title. ... 1945 (MCMVL) was a common year starting on Monday (the link is to a full 1945 calendar). ...

Description

To visualize the basic concept of simple sweep theory, consider a straight, non-swept wing of infinite length, which meets the airflow at a perpendicular angle. The resulting air pressure distribution is equivalent to the length of the wing's chord (the distance from the leading edge to the trailing edge). If we were to begin to slide the wing sideways (spanwise), the sideways motion of the wing relative to the air would be added to the previously perpendicular airflow, resulting in an airflow over the wing at an angle to the leading edge. This angle results in airflow traveling a greater distance from leading edge to trailing edge, and thus the air pressure is distributed over a greater distance (and consequently lessened at any particular point on the surface). Chord may mean: Chord (geometry), a line segment joining two points on a curve Chord (graph theory), an edge joining two not-adjacent nodes in a cycle Chord (music), an aggregate of musical pitches sounded simultaneously Chord (aviation), the distance between the front and back of a wing, measured in...

This scenario is identical to the airflow experienced by a swept wing as it travels through the air. The airflow over a swept wing encounters the wing at an angle. That angle can be broken down into two vectors, one perpendicular to the wing, and one parallel to the wing. The flow parallel to the wing has no affect on it, and since the perpendicular vector is shorter (meaning slower) than the actual airflow, it consequently exerts less pressure on the wing. In other words, the wing experiences airflow that is slower - and at lower pressures - than the actual speed of the aircraft.

One of the factors that must be taken into account when designing a high-speed wing is compressibility, which is the effect that acts upon a wing as it approaches and passes through the speed of sound. The significant negative effects of compressibility made it a prime issue with aeronautical engineers. Sweep theory helps mitigate the effects of compressibility in transonic and supersonic aircraft because of the reduced pressures. This allows the mach number of an aircraft to be higher than that actually experienced by the wing. Fluid Dynamics Compressibility (physics) is a measure of the relative volume change of fluid or solid as a response to a pressure (or mean stress) change: . For a gas the magnitude of the compressibility depends strongly on whether the process is adiabatic or isothermal, while this difference is small in... The speed of sound is a term used to describe the speed of sound waves passing through an elastic medium. ... Mach number (Ma) (pronounced: mæk, mɑːk) is defined as a ratio of the speed of an object or flow relative to the speed of sound in the medium through which it is travelling: Vo/Vs where Vo is the speed of the object and Vs is the speed...

There is also a negative aspect to sweep theory. The lift produced by a wing (called the coefficient of lift, or C_L), is directly related to the speed of the air over the wing. Since the airflow speed experienced by a swept wing is lower than what the actual aircraft speed is, this becomes a problem during slow-flight phases, such as takeoff and landing. There have been various ways of addressing the problem, including the variable-incidence wing design on the F-8 Crusader and swing-wings on the F-14, F-111, and the Panavia Tornado. The coefficient of lift is a number associated with a particular shape of an aerofoil, and is incorporated in the lift equation to predict the lift force generated by a wing using this particular cross section. ... The F-8 Crusader (originally F8U) was an aircraft carrier-based fighter aircraft built by Chance-Vought of Dallas, Texas. ... Sailors prepare an F-14 Tomcat for flight on the aircraft carrier USS Abraham Lincoln, in support of Operation Iraqi Freedom (2003). ... A U.S. Air Force F-111 The General Dynamics F-111 Aardvark (the nickname was unofficial for most of its lifespan, but it was officially named Aardvark at its retirement ceremony for the United States Air Force) is a long-range strategic bomber, reconnaissance, and tactical strike aircraft. ... The Panavia Tornado is a family of twin-engine fighters, which was jointly developed by the United Kingdom, Germany and Italy. ...

References

• Simple sweep theory math
• Advanced math of swept and oblique wings
• Sweep theory in a 3D environment