One of a series of wonderful films made by the Shell Oil Co., "High Speed Flight simplified version" -- presents material from three previous Shell films -- "Approaching the Speed of Sound", "Transonic Flight" and "Beyond the Speed of Sound". "High Speed Flight" gives an overview of the challenges of flying close to or above the speed of sound, and features a variety of British jet aircraft to demonstrate the design principles at work. It describes how sound travels, Mach speeds, the concepts of compressibility, and more. In short, the film discusses and explains the behavior of air flow at speeds approaching, at, and beyond the speed of sound, and demonstrates the effects on aircraft, and points out modifications necessary to overcome resulting problems.
Some of the aircraft shown include the Bristol 188, a British supersonic research aircraft built by the Bristol Aeroplane Company in the 1950s, the Boeing 707 prototype at 11:10, and others. We're having trouble identifying the aircraft in this film -- what is the one at 11:14? -- so if you can help please comment below!
In high-speed flight the assumptions of incompressibility of the air used in low-speed aerodynamics no longer apply. In subsonic aerodynamics, the theory of lift is based upon the forces generated on a body and a moving gas in which it is immersed. At airspeeds below about 260 knots, air can be considered incompressible, in that at a fixed altitude, its density remains nearly constant while its pressure varies. Under this assumption, air acts the same as water and is classified as a fluid.
Subsonic aerodynamic theory also assumes the effects of viscosity the property of a fluid that tends to prevent motion of one part of the fluid with respect to another are negligible, and classifies air as an ideal fluid, conforming to the principles of ideal-fluid aerodynamics such as continuity, Bernoulli's principle, and circulation. In reality, air is compressible and viscous. While the effects of these properties are negligible at low speeds, compressibility effects in particular become increasingly important as airspeed increases.
Compressibility and to a lesser extent viscosity is of paramount importance at speeds approaching the speed of sound. In these transonic speed ranges, compressibility causes a change in the density of the air around an airplane.
During flight, a wing produces lift by accelerating the airflow over the upper surface. This accelerated air can, and does, reach supersonic speeds, even though the airplane itself may be flying at a subsonic airspeed Mach number less than 1.0. At some extreme angles of attack, in some airplanes, the speed of the air over the top surface of the wing may be double the airplane’s airspeed. It is therefore entirely possible to have both supersonic and subsonic airflow on an airplane at the same time. When flow velocities reach sonic speeds at some location on an airplane such as the area of maximum camber on the wing, further acceleration will result in the onset of compressibility effects such as shock wave formation, drag increase, buffeting, stability, and control difficulties. Subsonic flow principles are invalid at all speeds above this point.
In high-speed flight the assumptions of incompressibility of the air used in low-speed aerodynamics no longer apply. In subsonic aerodynamics, the theory of lift is based upon the forces generated on a body and a moving gas in which it is immersed. At airspeeds below about 260 knots, air can be considered incompressible, in that at a fixed altitude, its density remains nearly constant while its pressure varies. Under this assumption, air acts the same as water and is classified as a fluid.
Subsonic aerodynamic theory also assumes the effects of viscosity are negligible, and classifies air as an ideal fluid, conforming to the principles of ideal-fluid aerodynamics such as continuity, Bernoulli's principle, and circulation. In reality, air is compressible and viscous. While the effects of these properties are negligible at low speeds, compressibility effects in particular become increasingly important as airspeed increases. Compressibility is of paramount importance at speeds approaching the speed of sound. In these transonic speed ranges, compressibility causes a change in the density of the air around an airplane.
This film is part of the Periscope Film LLC archive, one of the largest historic military, transportation, and aviation stock footage collections in the USA. Entirely film backed, this material is available for licensing in 24p HD, 2k and 4k. For more information visit http://www.PeriscopeFilm.com
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