Closed wing
Encyclopedia
Wing
A wing is an appendage with a surface that produces lift for flight or propulsion through the atmosphere, or through another gaseous or liquid fluid...
planform
Planform
In aviation, a planform is the shape and layout of a fixed-wing aircraft's fuselage and wing. Of all the myriad planforms used, they can typically be grouped into those used for low-speed flight, found on general aviation aircraft, and those used for high-speed flight, found on many military...
concept. The term closed wing encompasses a number of designs, including the annular wing (commonly known as the cylindrical or ring wing), the joined wing, and the box wing. A closed wing can be thought of as the maximum expression of a wingtip device, which has the aim of eliminating the influence of the wingtip vortices
Wingtip vortices
Wingtip vortices are tubes of circulating air that are left behind a wing as it generates lift. One wingtip vortex trails from the tip of each wing. The cores of vortices spin at very high speed and are regions of very low pressure...
which occur at the tips of conventional wings. These vortices form a major component of wake turbulence
Wake turbulence
Wake turbulence is turbulence that forms behind an aircraft as it passes through the air. This turbulence includes various components, the most important of which are wing vorticies and jetwash. Jetwash refers simply to the rapidly moving gases expelled from a jet engine; it is extremely turbulent,...
and are associated with induced drag, which negatively affects aerodynamic performance in most regimes. A closed wing surface has no wingtips whatsoever, and thus is capable of greatly reducing or eliminating wingtip drag
Drag (physics)
In fluid dynamics, drag refers to forces which act on a solid object in the direction of the relative fluid flow velocity...
, which has great implications for the improvement of fuel efficiency
Fuel efficiency
Fuel efficiency is a form of thermal efficiency, meaning the efficiency of a process that converts chemical potential energy contained in a carrier fuel into kinetic energy or work. Overall fuel efficiency may vary per device, which in turn may vary per application, and this spectrum of variance is...
in the airline industry.
Performance benefits
Lift-induced drag
In aerodynamics, lift-induced drag, induced drag, vortex drag, or sometimes drag due to lift, is a drag force that occurs whenever a moving object redirects the airflow coming at it. This drag force occurs in airplanes due to wings or a lifting body redirecting air to cause lift and also in cars...
for a given lift
Lift (force)
A fluid flowing past the surface of a body exerts a surface force on it. Lift is the component of this force that is perpendicular to the oncoming flow direction. It contrasts with the drag force, which is the component of the surface force parallel to the flow direction...
, wingspan
Wingspan
The wingspan of an airplane or a bird, is the distance from one wingtip to the other wingtip. For example, the Boeing 777 has a wingspan of about ; and a Wandering Albatross caught in 1965 had a wingspan of , the official record for a living bird.The term wingspan, more technically extent, is...
, and vertical extent. Annular and joined wings can achieve span efficiencies greater than 1, and the annular wing exhibits half the vortex drag of a monoplane
Monoplane
A monoplane is a fixed-wing aircraft with one main set of wing surfaces, in contrast to a biplane or triplane. Since the late 1930s it has been the most common form for a fixed wing aircraft.-Types of monoplane:...
wing of the same span and lift. However, the concept of eliminating the influence of tip vortices through use of closed wings is an ill-conceived notion, according to Dr. Ilan Kroo, Professor of Aeronautics and Astronautics at Stanford University
Stanford University
The Leland Stanford Junior University, commonly referred to as Stanford University or Stanford, is a private research university on an campus located near Palo Alto, California. It is situated in the northwestern Santa Clara Valley on the San Francisco Peninsula, approximately northwest of San...
. There appears to be no particular advantage to a fully closed design; despite a decrease in local loading on any given point on the wing, the circulation is constant, thereby causing no change in the wake
Wake
A wake is the region of recirculating flow immediately behind a moving or stationary solid body, caused by the flow of surrounding fluid around the body.-Fluid dynamics:...
, and thereby the lift and interference drag associated with the surface. For this reason, closed wings remain mostly confined to the realms of studies and conceptual designs, as the engineering challenges of developing a strong, self-supporting closed wing for use in the large airliners which would benefit most from increases in efficiency have yet to be overcome. The C-wing benefits from many of the drag-reducing benefits of a closed wing design without the downsides of being a fully closed system.
The closed wing concept is also used in the water medium, in surfboard
Surfboard
A surfboard is an elongated platform used in the sport of surfing. Surfboards are relatively light, but are strong enough to support an individual standing on them while riding a breaking wave...
fins also known as tunnel fins
Tunnel fins
The Tunnel fin is a type of surfboard fin used on surfboards, especially heavy longboards and longboard guns. The weight and length of these boards make it easier to control the fore and aft angle of the tunnel.As the name suggests it is shaped like a tunnel...
.
History
Blériot III
-Bibliography:* Phillipps, Brian A. Bleriot: Herald of an Age. Stroud: Tempus, 2000 ISBN0 75241739 8* Hallion, Richard P. 'Taking Flight. New York: Oxford University Press, 2003. ISBN 0 19 516035 5...
aircraft, built in 1906 by Louis Blériot
Louis Blériot
Louis Charles Joseph Blériot was a French aviator, inventor and engineer. In 1909 he completed the first flight across a large body of water in a heavier-than-air craft, when he crossed the English Channel. For this achievement, he received a prize of £1,000...
and Gabriel Voisin
Gabriel Voisin
Gabriel Voisin was an aviation pioneer and the creator of Europe's first manned, engine-powered, heavier-than-air aircraft capable of a sustained , circular, controlled flight, including take-off and landing. It was flown by Henry Farman on January 13, 1908 near Paris, France...
. The aircraft's lifting structure consisted of two annular wings mounted in tandem, with two tractor propellers powered by an engine mounted inside the diameter of the forward wing. The Blériot IV was a variation on this design, which replaced the forward annular wing with a canard biplane setup similar to the 1903 Wright Flyer
Wright Flyer
The Wright Flyer was the first powered aircraft, designed and built by the Wright brothers. They flew it four times on December 17, 1903 near the Kill Devil Hills, about four miles south of Kitty Hawk, North Carolina, U.S.The U.S...
. This aircraft was able to leave the ground in a series of small hops before being damaged beyond repair. An aircraft known as the "Kitchen Doughnut" flew in Chicago
Chicago
Chicago is the largest city in the US state of Illinois. With nearly 2.7 million residents, it is the most populous city in the Midwestern United States and the third most populous in the US, after New York City and Los Angeles...
in 1911; it had two ring wings, one mounted atop the other.
George Tilghman Richards and Cedric Lee designed an annular wing monoplane. Flown by Gordon England in 1913; it crashed but a second was built. After that was wrecked, a third was completed and flown.
In 1944, the German
Nazi Germany
Nazi Germany , also known as the Third Reich , but officially called German Reich from 1933 to 1943 and Greater German Reich from 26 June 1943 onward, is the name commonly used to refer to the state of Germany from 1933 to 1945, when it was a totalitarian dictatorship ruled by...
designer Ernst Heinkel
Ernst Heinkel
Dr. Ernst Heinkel was a German aircraft designer, manufacturer, Wehrwirtschaftführer in the Third Reich, and member of the Nazi party. His company Heinkel Flugzeugwerke produced the Heinkel He 178, the world's first turbojet aircraft and jet plane, and the Heinkel He 176, the first rocket aircraft...
began working on an annular-wing VTOL
VTOL
A vertical take-off and landing aircraft is one that can hover, take off and land vertically. This classification includes fixed-wing aircraft as well as helicopters and other aircraft with powered rotors, such as cyclogyros/cyclocopters and tiltrotors...
multirole single-seater called Lerche
Heinkel Lerche
-See also:-Notes & References:* Luftwaffe Secret Projects - Ground Attack & Special Purpose Aircraft, D. Herwig & H. Rode, ISBN 1-85780-150-4*...
, but the project was abandoned.
During the 1950s, the French company SNECMA
Snecma
Snecma is a major French manufacturer of engines for commercial and military aircraft, and for space vehicles. The name is an acronym for Société Nationale d'Étude et de Construction de Moteurs d'Aviation .In 2005, the Snecma group, which included Snecma ,...
developed an aircraft called the Coléoptère
SNECMA Coléoptère
The SNECMA Coléoptère was a VTO aircraft developed by the French in the 1950s. It was a single-person aircraft with an annular wing designed to land vertically, therefore requiring no runway and very little space to take-off. There were several prototypes developed and tested, however the design...
, a single-person VTOL
VTOL
A vertical take-off and landing aircraft is one that can hover, take off and land vertically. This classification includes fixed-wing aircraft as well as helicopters and other aircraft with powered rotors, such as cyclogyros/cyclocopters and tiltrotors...
design equipped with an annular wing. Despite the development and testing of several prototypes, the aircraft proved unstable and largely unsafe, and the design was abandoned. Later proposals for closed-wing designs included the Convair
Convair
Convair was an American aircraft manufacturing company which later expanded into rockets and spacecraft. The company was formed in 1943 by the merger of Vultee Aircraft and Consolidated Aircraft, and went on to produce a number of pioneering aircraft, such as the Convair B-36 bomber, and the F-102...
Model 49 Advanced Aerial Fire Support System (AAFSS), and the 1980s Lockheed
Lockheed Martin
Lockheed Martin is an American global aerospace, defense, security, and advanced technology company with worldwide interests. It was formed by the merger of Lockheed Corporation with Martin Marietta in March 1995. It is headquartered in Bethesda, Maryland, in the Washington Metropolitan Area....
concept known as the "Flying Bog Seat".
The modern idea of the joined wing was developed principally by Dr. Julian Wolkovitch in the 1980s, as an efficient structural arrangement in which the horizontal tail was used as a structural support for the main wing as well as a stabilizing surface.
The Spiroid winglet
Winglet
Wingtip devices are usually intended to improve the efficiency of fixed-wing aircraft. There are several types of wingtip devices, and though they function in different manners, the intended effect is always to reduce the aircraft's drag by partial recovery of the tip vortex energy...
, a design currently under development by Aviation Partners
Aviation Partners Inc.
Aviation Partners Inc. or API is a Seattle-based private corporation, which specializes in the production of performance enhancing winglet systems...
, is a closed wing surface mounted at the end of a conventional wing. Initial testing using a Gulfstream II test aircraft has shown the winglet design to reduce fuel consumption in the cruise phase by over 10%.
Aeronautical engineers in Belarus
Belarus
Belarus , officially the Republic of Belarus, is a landlocked country in Eastern Europe, bordered clockwise by Russia to the northeast, Ukraine to the south, Poland to the west, and Lithuania and Latvia to the northwest. Its capital is Minsk; other major cities include Brest, Grodno , Gomel ,...
designed and constructed planes with ellipse wings, which allow the wings size of the plane to be kept small, and with the attached air vortexes on the sides of the wings help increase power by about 30%. The ellipse wings also maintain a sustainable hold on the plane keeping it more firm in all conditions.
Design studies
A Finnish company "Flynano" is currently (fall 2011) in prototype testing phase of a closed wing ultralight aircraft.Several other types have been proposed but have not been built.
Proposals with the wing mounted on top of the fuselage
External links
External media
- Convair Model 49 image
- Amateur wind tunnel testing of planar and annular wings—YouTubeYouTubeYouTube is a video-sharing website, created by three former PayPal employees in February 2005, on which users can upload, view and share videos....
video
