Transonic

F/A-18 flying at transonic speed

Transonic is an aeronautics term referring to a range of velocities just below and above the speed of sound (about mach 0.8–1.2). It is defined as the range of speeds between the critical mach number, when some parts of the airflow over an aircraft become supersonic, and a higher speed, typically near Mach 1.2, when all of the airflow is supersonic. Between these speeds some of the airflow is supersonic, and some is not.

Most modern jet powered aircraft spend a considerable amount of time in the transonic state. This is particularly important due to an effect known as wave drag, which is prevalent in these speed ranges. Attempts to combat wave drag can be seen on all high-speed aircraft; most notable is the use of swept wings, but another common form is a wasp-waist fuselage as a side effect of the Whitcomb area rule.

Severe instability can occur at transonic speeds. Shock waves move through the air at the speed of sound. When an object such as an aircraft also moves at the speed of sound, these shock waves build up in front of it to form a single, very large shock wave. During transonic flight, the plane must pass through this large shock wave, as well as contending with the instability caused by air moving faster than sound over parts of the wing and slower in other parts. The difference in speed is due to Bernoulli's principle.

Transonic speeds can also occur at the tips of rotor blades of helicopters and aircraft. However, as this puts severe, unequal stresses on the rotor blade, it is avoided and may lead to dangerous accidents if it occurs. It is one of the limiting factors to the size of rotors, and also to the forward speeds of helicopters (as this speed is added to the forward-sweeping (leading) side of the rotor, thus possibly causing localized transonics).

Interesting facts

Transonic flow patterns on an airfoil showing flow patterns at and above critical Mach number.

At transonic speeds intense low-pressure areas form at various points around an aircraft. If conditions are right (i.e. high humidity) visible clouds will form in these low-pressure areas as shown in the illustration; these are called Prandtl-Glauert singularities. These clouds remain with the aircraft as it travels. It is not necessary for the aircraft as a whole to reach supersonic speeds for these clouds to form.

References

Theory of transonic astrophysical flows: Sandip K. Chakrabarti, World Scientific Publishers , Singapore (1990)

Aeronautics is the science involved with the study, design, and manufacture of flight-capable machines, or the techniques of operating aircraft. While the term—literally meaning "sailing the air"—originally referred solely to the science of operating
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speed of sound describes how much distance such a wave travels in a given amount of time. In dry air, at a temperature of 21 °C (70 °F) the speed of sound is 344 m/s (1238 km/h, or 769 mph, or 1128 ft/s).
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Critical mach is an aeronautics term that refers to the speed at which some of the airflow on a wing becomes supersonic. When this occurs the distribution of forces on the wing changes suddenly and dramatically, typically leading to a strong nose-down force on the aircraft.
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supersonic. Speeds greater than 5 times the speed of sound are sometimes referred to as hypersonic. Speeds where only some parts of the air around an object (such as the ends of rotor blades) reach supersonic speeds are labelled transonic (typically somewhere between Mach 0.
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Mach number (Ma) (pronounced: [mɑːk], [mɑx], [mæk], see IPA) is a dimensionless measure of relative speed.
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jet engine is an engine that discharges a fast moving jet of fluid to generate thrust in accordance with Newton's . This broad definition of jet engines includes turbojets, turbofans, rockets, ramjets, pulse jets and pump-jets, but in common usage, the term generally refers to a
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Wave drag is an aerodynamics term that refers to a sudden and very powerful form of drag that appears on aircraft flying at high-subsonic and supersonic speeds.

Overview

Wave drag is caused by the formation of shock waves around the aircraft.
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swept-wing is a wing planform common on high-speed aircraft, with the wing swept back instead of being set at right angles to the fuselage. Forward sweep is also used on some aircraft.
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The Whitcomb area rule, also called the supersonic area rule, is a design technique used to reduce an aircraft's drag at transonic and supersonic speeds, particularly between Mach 0.8 and 1.2.
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Bernoulli's equation redirects here; see Bernoulli differential equation for an unrelated topic in ordinary differential equations.

Bernoulli's Principle
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Rotorcraft is a category of heavier-than-air flying machines that use lift generated by wings that revolve around a mast called rotor blades. Several rotor blades mounted to a single mast is referred to as a rotor.
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Prandtl-Glauert singularity (sometimes referred to as a "vapor cone"), is the point at which a sudden drop in air pressure occurs, and is generally accepted as the cause of the visible condensation cloud that often surrounds an aircraft travelling at transonic speeds, though there
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Critical Mach number (Mcr) is the maximum Mach number (airspeed in relation to the speed of sound - Mach 1.0) which a subsonic aircraft can attain whilst still remaining controllable by the pilot.
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Sound Barrier was a heavy metal band from Los Angeles from 1980 to 1987.

Biography

Sound Barrier was most notable for the fact that all four members were African American, which garnered them significant publicity, but which didn't result in commercial success.
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Anti-shock bodies or Küchemann carrots are pods placed at the trailing edge of a subsonic aircraft's wings in order to reduce wave drag, thus improving fuel economy, as the aircraft enters the transonic flight regime (Mach 0.8–1.2).
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hypersonic speeds are speeds that are highly supersonic. In the 1970s, the term generally came to refer to speeds of Mach 5 (5 times the speed of sound) and above. The hypersonic regime is a subset of the supersonic regime.
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Interesting facts

See also

Other Flow Regimes

References

Overview

Biography

Transonic playV2('en/US/dh/dhsfsgdgsjsysfsfskd5gh');playV2('en/UK/dh/dhsfsgdgsjsysfsfskd5gh')

Interesting facts

See also

Other Flow Regimes

References

Overview

Biography

Transonic