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N-wave
A sonic boom is a sound associated with shock waves created when an object travels through the air faster than the speed of sound. Sonic booms generate enormous amounts of sound energy, sounding similar to an explosion or a thunderclap to the human ear. The crack of a supersonic bullet passing overhead or the crack of a bullwhip are examples of a small sonic boom. Sonic booms due to large supersonic aircraft can be particularly loud and startling, tend to awaken people, and may cause minor damage to some structures. This led to the prohibition of routine supersonic flight overland. Although sonic booms cannot be completely prevented, research suggests that with careful shaping of the vehicle, the nuisance due to sonic booms may be reduced to the point that overland supersonic flight may become a feasible option. A sonic boom does not occur only at the moment an object crosses the sound barrier and neither is it heard in all directions emanating from the supersonic objec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Supersonic Aircraft
A supersonic aircraft is an aircraft capable of supersonic flight, that is, flying faster than the speed of sound (Mach number, Mach 1). Supersonic speed, Supersonic aircraft were developed in the second half of the twentieth century. Supersonic aircraft have been used for research and military purposes, but only two supersonic aircraft, the Tupolev Tu-144 (first flown on December 31, 1968) and the Concorde (first flown on March 2, 1969), ever entered service Supersonic transport, for civil use as airliners. Fighter aircraft, Fighter jets are the most common example of supersonic aircraft. The aerodynamics of supersonic flight is called compressible flow because of the compression (physics), compression associated with the shock waves or "sonic boom" created by any object traveling faster than sound. Aircraft flying at speeds above Mach 5 are called Hypersonic flight, hypersonic aircraft. Supersonic speed is reckoned with respect to air speed; higher speeds can be achieved in te ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Red Carpet
A red carpet is traditionally used to mark the route taken by heads of state on ceremonial and formal occasions, and has in recent decades been extended to use by Very Important Person, VIPs and celebrity, celebrities at formal events. History The earliest known reference to walking a red carpet in literature is in the play ''The Oresteia, Agamemnon'' by Aeschylus, written in 458 BC. When the title character returns from Troy, he is greeted by his wife Clytemnestra who offers him a red path to walk upon: Agamemnon, knowing that only Greek mythology, gods walk on such luxury, responds with trepidation: Oriental carpets in Renaissance painting, Renaissance paintings often show rugs and carpets in oriental patterns, with red often the main background colour, laid on the steps to a throne, or on a dais where rulers or sacred figures are placed. A red carpet was rolled out to welcome the arrival of United States president James Monroe in South Carolina in 1821. In 1902, the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bow Wave
A bow wave is the wave that forms at the bow (watercraft), bow of a ship when it moves through the water. As the bow wave spreads out, it defines the outer limits of a ship's Wake (physics), wake. A large bow wave slows the ship down, is a risk to smaller boats, and in a harbor can damage shore facilities and moored ships. Therefore, Hull (watercraft), ship hulls are generally designed to produce as small a bow wave as possible. Description The size of the bow wave is a function of the speed of the ship, its Draft (hull), draft, Ocean surface wave, surface waves, water depth, and the shape of the bow. A ship with a large Draft (hull), draft and a blunt bow will produce a large wave, and ships that Planing (sailing), plane over the water surface will create smaller bow waves. Bow wave patterns are studied in the field of computational fluid dynamics. The bow wave carries energy away from the ship at the expense of its kinetic energy—it slows the ship. A major goal of naval arch ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vapour Cone
A vapor cone (also known as a Mach diamond, shock collar, or shock egg) is a visible cloud of condensed water that can sometimes form around an object moving at high speed through moist air, such as an aircraft flying at transonic speeds. When the localized air pressure around the object drops, so does the air temperature. If the temperature drops below the saturation temperature, a cloud forms. In the case of aircraft, the cloud is caused by expansion fans decreasing the air pressure, density, and temperature below the dew point. Then pressure, density, and temperature suddenly increase across the stern shock wave associated with a return to subsonic flow behind the aircraft. Since the local Mach number is not uniform over the aircraft, parts of the aircraft may be supersonic while others remain subsonic—a flight regime called transonic flight. In addition to making the shock waves themselves visible, water condensation can also occur in the trough between two crests of the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mach Number
The Mach number (M or Ma), often only Mach, (; ) is a dimensionless quantity in fluid dynamics representing the ratio of flow velocity past a boundary to the local speed of sound. It is named after the Austrian physicist and philosopher Ernst Mach. \mathrm = \frac, where: * is the local Mach number, * is the local flow velocity with respect to the boundaries (either internal, such as an object immersed in the flow, or external, like a channel), and * is the speed of sound in the medium, which in air varies with the square root of the thermodynamic temperature. By definition, at Mach1, the local flow velocity is equal to the speed of sound. At Mach0.65, is 65% of the speed of sound (subsonic), and, at Mach1.35, is 35% faster than the speed of sound (supersonic). The local speed of sound, and hence the Mach number, depends on the temperature of the surrounding gas. The Mach number is primarily used to determine the approximation with which a flow can be treated as an i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Overpressure
Overpressure (or blast overpressure) is the pressure caused by a shock wave over and above normal atmospheric pressure. The shock wave may be caused by sonic boom or by explosion An explosion is a rapid expansion in volume of a given amount of matter associated with an extreme outward release of energy, usually with the generation of high temperatures and release of high-pressure gases. Explosions may also be generated ..., and the resulting overpressure receives particular attention when measuring the effects of nuclear weapons or thermobaric bombs. Effects According to an article in the journal '' Toxicological Sciences'', Blast overpressure (BOP), also known as high energy impulse noise, is a damaging outcome of explosive detonations and firing of weapons. Exposure to BOP shock waves alone results in injury predominantly to the hollow organ systems such as auditory, respiratory, and gastrointestinal systems. An EOD suit worn by bomb disposal experts can protect ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pascal (unit)
The pascal (symbol: Pa) is the unit of pressure in the International System of Units (SI). It is also used to quantify internal pressure, stress, Young's modulus, and ultimate tensile strength. The unit, named after Blaise Pascal, is an SI coherent derived unit defined as one newton per square metre (N/m2). It is also equivalent to 10 barye (10 Ba) in the CGS system. Common multiple units of the pascal are the hectopascal (1 hPa = 100 Pa), which is equal to one millibar, and the kilopascal (1 kPa = 1000 Pa), which is equal to one centibar. The unit of measurement called '' standard atmosphere (atm)'' is defined as . Meteorological observations typically report atmospheric pressure in hectopascals per the recommendation of the World Meteorological Organization, thus a standard atmosphere (atm) or typical sea-level air pressure is about 1013 hPa. Reports in the United States typically use inches of mercury or millibars (hectopascals). In Cana ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
P-wave
A P wave (primary wave or pressure wave) is one of the two main types of elastic body waves, called seismic waves in seismology. P waves travel faster than other seismic waves and hence are the first signal from an earthquake to arrive at any affected location or at a seismograph. P waves may be transmitted through gases, liquids, or solids. Nomenclature The name ''P wave'' can stand for either pressure wave (as it is formed from alternating compressions and rarefactions) or primary wave (as it has high velocity and is therefore the first wave to be recorded by a seismograph). The name '' S wave'' represents another seismic wave propagation mode, standing for secondary or shear wave, a usually more destructive wave than the primary wave. Seismic waves in the Earth Primary and secondary waves are body waves that travel within the Earth. The motion and behavior of both P and S waves in the Earth are monitored to probe the interior structure of the Earth. Discontinuities ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ground Motion
Ground motion is the movement of the Earth’s surface from earthquakes or explosions. Ground motion is produced by seismic waves that are generated by sudden slip on a fault or sudden pressure at the explosive source and travel through the Earth and along its surface. This can be due to natural events, such as earthquakes and volcanic eruptions, or human activities, such as the detonation of nuclear weapons. There are two main types of seismic waves: body waves and surface waves. Body waves travel through the interior of the Earth, while surface waves travel along the Earth's surface. Ground motion is typically caused by surface waves, which are the most destructive type of seismic waves. Ground motion is measured using a seismometer A seismometer is an instrument that responds to ground displacement and shaking such as caused by quakes, volcanic eruptions, and explosions. They are usually combined with a timing device and a recording device to form a seismograph. The ou ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
