Supercritical airfoil

A supercritical airfoil is an airfoil designed, primarily, to delay the onset of wave drag in the transonic speed range. Supercritical airfoils are characterized by their flattened upper surface, highly cambered (curved) aft section, and larger leading edge radius compared with NACA 6-series laminar airfoil shapes. Standard wing shapes are designed to create lower pressure over the top of the wing by accelerating the air using the Bernoulli's principle. The camber of the wing determines how much the air accelerates around the wing. As the speed of the aircraft approaches the speed of sound the air accelerating around the wing will reach the Mach 1 and shockwaves will begin to form. The formation of these shockwaves causes wave drag. Supercritical airfoils are designed to minimize this effect by flattening the upper surface of the wing.

The supercritical airfoils were suggested first in Germany in 1940, when K.A. Kawalki at Deutsche Versuchsanstalt für Luftfahrt Berlin-Adlershof designed airfoils characterised by elliptical leading edges, maximum thickness located downstream up to 50 per cent chord and a flat upper surface. Testing of these airfoils was reported by B. Göthert and K.A. Kawalki in 1944. Kawalki's airfoil shapes were identical to Richard Whitcomb's. Hawker-Siddeley in Hatfield, England designed in 1959-1965 improved airfoil profiles known as rooftop rear-loaded airfoils, which were the basis of the Airbus A300 supercritical wing, which first flew in 1972.

Mach number

In fluid dynamics, the Mach number (M or Ma) (/mɑːx/; German: [maχ]) is a dimensionless quantity representing the ratio of flow velocity past a boundary to the local speed of sound.

where

The local speed of sound, and thereby the Mach number, depends on the condition of the surrounding medium, in particular the temperature and pressure. The Mach number is primarily used to determine the approximation with which a flow can be treated as an incompressible flow. The medium can be a gas or a liquid. The boundary can be traveling in the medium, or it can be stationary while the medium flows along it, or they can both be moving, with different velocities: what matters is their relative velocity with respect to each other. The boundary can be the boundary of an object immersed in the medium, or of a channel such as a nozzle, diffusers or wind tunnels chaneling the medium. As the Mach number is defined as the ratio of two speeds, it is a dimensionless number. If M < 0.2–0.3 and the flow is quasi-steady and isothermal, compressibility effects will be small and a simplified incompressible flow equations can be used.

Research institute

A research institute is an establishment endowed for doing research. Research institutes may specialize in basic research or may be oriented to applied research. Although the term often implies natural science research, there are also many research institutes in the social sciences as well, especially for sociological and historical research purposes.

Famous research institutes

In the early medieval period, several astronomical observatories were built in the Islamic world. The first of these was the 9th-century Baghdad observatory built during the time of the Abbasid caliph al-Ma'mun, though the most famous were the 13th-century Maragheh observatory, 15th-century Ulugh Beg Observatory.

The earliest research institute in Europe was Tycho Brahe's Uraniborg complex on the island of Hven, a 16th-century astronomical laboratory set up to make highly accurate measurements of the stars. In the United States there are numerous notable research institutes including Bell Labs, The Scripps Research Institute,Beckman Institute, and SRI International. Hughes Aircraft used a research institute structure for its organizational model.

Shock wave

In physics, a shock wave or shock is a type of propagating disturbance. When a wave moves faster than the local speed of sound in a fluid it is a shock wave. Like an ordinary wave, a shock wave carries energy, and can propagate through a medium; however it is characterized by an abrupt, nearly discontinuous change in pressure, temperature and density of the medium. In supersonic flows, expansion is achieved through an expansion fan also known as a Prandtl-Meyer expansion fan.

Unlike solitons (another kind of nonlinear wave), the energy of a shock wave dissipates relatively quickly with distance. Also, the accompanying expansion wave approaches and eventually merges with the shock wave, partially cancelling it out. Thus the sonic boom associated with the passage of a supersonic aircraft is the sound wave resulting from the degradation and merging of the shock wave and the expansion wave produced by the aircraft.

When a shock wave passes through matter, energy is preserved but entropy increases. This change in the matter's properties manifests itself as a decrease in the energy which can be extracted as work, and as a drag force on supersonic objects; shock waves are strongly irreversible processes.

Armstrong Flight Research Center

The Armstrong Flight Research Center, located inside Edwards Air Force Base, is an aeronautical research center operated by NASA. It was originally named in honor of Hugh L. Dryden, a prominent aeronautical engineer who at the time of his death in 1965 was NASA's deputy administrator, and it is still variously known as Dryden or the Dryden Flight Research Center (DFRC) while the details of the name change are decided (the name change to AFRC went into effect on March 1, 2014). First known as the National Advisory Committee for Aeronautics Muroc Flight Test Unit, the DFRC has also been known as the High-Speed Flight Research Station (1949) and the High-Speed Flight Station (1954). The facility was renamed, effective March 1, 2014, the Armstrong Flight Research Center in honor of Neil Armstrong, the first human being to walk on the surface of the moon. Similarly the Western Aeronautical Test Range at the facility was renamed the NASA Hugh L. Dryden Aeronautical Test Range.