articles - vortex and vtol
Vortex
A vortex can be any circular or rotary flow that possesses vorticity.
Vorticity is a mathematical concept used in fluid dynamics. It can be related to the amount of "circulation" or "rotation" in a fluid. In dluid dynamics, vorticity is the circulation per unit area at a point in the flow field. It is a vector quantity, whose direction is (roughly speaking) along the axis of the swirl. Also in fluid dynamics, the movement of a fluid can be said to be vortical if the fluid moves around in a circle, or in a helix, or if it tends to spin around some axis. Such motion can also be called solenoidal. In the atmospheric sciences, vorticity is a property that characterizes large-scale rotation of air masses. Since the atmospheric circulation is nearly horizontal, the (3 dimensional) vorticity is nearly vertical, and it is common to use the vertical component as a scalar vorticity.
A vortex can be seen in the spiralling motion of air or liquid around a center of rotation. Circular current of water of conflicting tides form vortex shapes. Turbulent flow makes many vortices. A good example of a vortex is the atmospheric phenomenon of a whirlwind or a tornado. This whirling air mass mostly takes the form of a helix, column, or spiral. Tornadoes develop from severe thunderstorms, usually spawned from squall lines and super cell thunderstorms, though they sometimes happen as a result of a hurricane.
A mesovortex is on the scale of a few miles (smaller than a hurricane but larger than a tornado). [2] On a much smaller scale, a vortex is usually formed as water goes down a drain, as in a sink or a toilet. This occurs in water as the revolving mass forms a whirlpool. This whirlpool is caused by water flowing out of a small opening in the bottom of a basin or reservoir. This swirling flow structure within a region of fluid flow opens downward from the water surface.
VTOL
Vertical Take-Off and Landing (VTOL) describes airplanes that can lift off vertically. This classification includes only a very few aircraft; helicopters are not considered VTOL. Some aircraft can operate in VTOL mode in addition to others, such as CTOL (Conventional Take-off and Landing). Others can only operate by VTOL, due to the aircraft lacking landing gear that can handle horizontal motion.
In 1928, Nikola Tesla received patents for an apparatus for aerial transportation. It is one of the earliest example of VTOL aircraft. In the late 1950s and early 1960s almost all fighter aircraft designed included some VTOL features. This was a response to the worrying possibility that a first-strike against airfields by nuclear armed bombers would leave a country open to attack by following bombers. The "solution" was to use VTOL fighters that could be moved to open fields around the countryside, making them immune to widespread destruction.
In reality the costs of VTOL performance were huge, and while it turned out to be fairly easy to move the plane, moving the support equipment and fuel was not so easy. By the mid-1960s interest in VTOL had faded, perhaps due much to the widespread introduction of ICBMs as the main nuclear delivery system.
Currently there are believed to be two types of practical VTOL aircraft in operation: Bell Boeing V-22 Osprey "tilt-rotor" and the British Aerospace Harrier "Jump jet" (or its updated American counterpart, the Boeing AV-8B Harrier II).
An early VTOL prototype was the so-called "flying bedstead".
The Harrier is often flown in STOVL mode which enables it to carry a higher fuel or weapon load over a given distance. It was developed from the Hawker P.1127 and Kestrel. The Indian and Spanish Navies operate Sea Harriers, mainly from aircraft carriers.
The United States Marine Corps uses a license-built derivative of the Harrier. NASA has flown other VTOL craft such as the XV-15 research craft, as have the Soviet Navy and Luftwaffe. Sikorsky tested an aircraft dubbed the X-Wing, which took off in the manner of a helicopter. The rotors would become stationary in mid-flight, and function as wings, providing lift in addition to the static wings.
The Soviet Yak-38 Forger was the Soviet Navy's VTOL aircraft for their light carriers, cargo ships, and capital ships. It was developed from the Yak-36 Freehand experimental aircraft. Before the Soviet Union collapsed, the only supersonic VTOL aircraft was developed as the Yak-38's successor, the Yak-141, which never went into production.
The Moller Skycar is a prototype personal VTOL aircraft -- literally, a "flying car".
Aircraft designed to operate in extraterrestrial environments often utilize VTOL. An example of this type of aircraft is the LLRV. Spacecraft typically operate in environments where runways or even a suitably flat surface for skids is nonexistent.