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Ground-effect vehicle
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Ground-effect vehicle
A ground-effect vehicle (GEV), also called a wing-in-ground-effect (WIGE or WIG), ground-effect craft/machine (GEM), wingship, flarecraft, surface effect vehicle or ekranoplan (Russian: экранопла́н – "screenglider"), is a vehicle that makes use of the ground effect, the aerodynamic interaction between a moving wing and the stationary surface below (land or water). Typically, it glides over a level surface (usually over water). Some models can operate over any flat area such as a lake or flat plains similar to a hovercraft. The term Ground-Effect Vehicle originally referred to any craft utilizing ground effect, including what later became known as hovercraft, in patent descriptions during the 1950s. However, this term came to exclude air-cushion vehicles or hovercraft. GEVs do not include racecars utilizing ground-effect for increasing downforce.
In aircraft, the ground effect is the reduced aerodynamic drag that an aircraft's wings generate when they are close to a surface (land or water).
The principal benefit of operating in ground effect is to reduce its lift-induced drag. The closer the wing operates to a surface such as the ground ("in ground effect"), the less drag it experiences. When an aircraft enters ground effect, the surface pushes back against the downwash, which reduces its drag.
During takeoff, ground effect can cause an aircraft to "float" while accelerating towards the climb speed, reducing friction.
Any airfoil passing through air increases air pressure on the underside, while decreasing pressure on the upper side, which generates lift. The high and low pressures are maintained until they flow off the ends of the wings, where they form vortices that are the major source of lift-induced drag—normally a significant portion of the total drag.
In GEV, the angle of attack is the angle between its chordline (a straight line from the leading edge to the trailing edge) and the ground. On takeoff, airplanes pitch their noses up to increase the angle of attack to reach the ideal of 12-20 degrees (depending on wing design and other factors).
Placing the wing near a surface has the same effect as increasing the aspect ratio because the surface prevents wingtip vortices from expanding, but without the complications associated with a long, slender wing. The stubby wings on a GEV can produce as much lift as the much larger wing on a transport aircraft, though only while close to the earth's surface. Once sufficient speed has built up, some GEVs can function as conventional aircraft until approaching a destination. However, they are unable to land or take off without a significant amount of help from the ground effect, and cannot climb until they have reached a much higher speed. The greater the wingspan, the less drag created for each unit of lift and the greater the efficiency of the wing.
GEVs are not statically supported upon a cushion of pressurized air from a downward-directed fan. Some GEV designs, such as the Russian Lun and Dingo, blew air under the wing using auxiliary engines to assist takeoff; however they still require forward motion to generate sufficient lift to fly, unlike hovercraft, also lacking low-speed hover capability. GEVs also have no contact with the surface when in flight.
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Ground-effect vehicle
A ground-effect vehicle (GEV), also called a wing-in-ground-effect (WIGE or WIG), ground-effect craft/machine (GEM), wingship, flarecraft, surface effect vehicle or ekranoplan (Russian: экранопла́н – "screenglider"), is a vehicle that makes use of the ground effect, the aerodynamic interaction between a moving wing and the stationary surface below (land or water). Typically, it glides over a level surface (usually over water). Some models can operate over any flat area such as a lake or flat plains similar to a hovercraft. The term Ground-Effect Vehicle originally referred to any craft utilizing ground effect, including what later became known as hovercraft, in patent descriptions during the 1950s. However, this term came to exclude air-cushion vehicles or hovercraft. GEVs do not include racecars utilizing ground-effect for increasing downforce.
In aircraft, the ground effect is the reduced aerodynamic drag that an aircraft's wings generate when they are close to a surface (land or water).
The principal benefit of operating in ground effect is to reduce its lift-induced drag. The closer the wing operates to a surface such as the ground ("in ground effect"), the less drag it experiences. When an aircraft enters ground effect, the surface pushes back against the downwash, which reduces its drag.
During takeoff, ground effect can cause an aircraft to "float" while accelerating towards the climb speed, reducing friction.
Any airfoil passing through air increases air pressure on the underside, while decreasing pressure on the upper side, which generates lift. The high and low pressures are maintained until they flow off the ends of the wings, where they form vortices that are the major source of lift-induced drag—normally a significant portion of the total drag.
In GEV, the angle of attack is the angle between its chordline (a straight line from the leading edge to the trailing edge) and the ground. On takeoff, airplanes pitch their noses up to increase the angle of attack to reach the ideal of 12-20 degrees (depending on wing design and other factors).
Placing the wing near a surface has the same effect as increasing the aspect ratio because the surface prevents wingtip vortices from expanding, but without the complications associated with a long, slender wing. The stubby wings on a GEV can produce as much lift as the much larger wing on a transport aircraft, though only while close to the earth's surface. Once sufficient speed has built up, some GEVs can function as conventional aircraft until approaching a destination. However, they are unable to land or take off without a significant amount of help from the ground effect, and cannot climb until they have reached a much higher speed. The greater the wingspan, the less drag created for each unit of lift and the greater the efficiency of the wing.
GEVs are not statically supported upon a cushion of pressurized air from a downward-directed fan. Some GEV designs, such as the Russian Lun and Dingo, blew air under the wing using auxiliary engines to assist takeoff; however they still require forward motion to generate sufficient lift to fly, unlike hovercraft, also lacking low-speed hover capability. GEVs also have no contact with the surface when in flight.
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