en>Daniele Pugliesi: removed Category:Thermodynamics; added Category:Thermodynamic systems using HotCat

2014-10-22T02:13:40Z

removed Category:Thermodynamics; added Category:Thermodynamic systems using HotCat

en>Headbomb: Undid revision 523982928 by Garuda0001 (talk) book added by COI editor, feel free to re-instate

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Undid revision 523982928 by Garuda0001 (talk) book added by COI editor, feel free to re-instate

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{{Infobox aviation
|name=Vortex generator
|image=Image:VortexGenerators01.JPG
|caption=After-market Micro Dynamics vortex generators mounted on the wing of a [[Cessna 182]]K
}}

[[File:Wind Turbine Vortex Generator.jpg|thumbnail|Sketch describing how vortex generators improve flow characteristics]]
[[Image:Cessna182withVotexGenerators02.jpg|thumb|1967 Model [[Cessna 182]]K in flight showing after-market vortex generators on the wing leading edge]]
[[File:TA-4SU Skyhawk cockpits.jpg|thumb|[[A-4SU Super Skyhawk|TA-4SU Super Skyhawk]] showing the row of vortex generators on the drooped [[leading edge slats]].]]
[[Image:SA-160VortexGenerators03.jpg|thumb|right|The [[Symphony SA-160]] was designed with two unusual vortex generators on its wing to ensure aileron effectiveness through the stall]]

A '''vortex generator''' (VG) is an [[aerodynamic]] surface, consisting of a small [[vane]] that creates a [[vortex]].<ref name="Peppler">Peppler, I.L.: ''From The Ground Up'', page 23. Aviation Publishers Co. Limited, Ottawa Ontario, Twenty Seventh Revised Edition, 1996. ISBN 0-9690054-9-0</ref><ref name="MicroHow">{{cite web|url = http://www.microaero.com/pages/v_howvgswrk.html|title = How Micro VGs Work|accessdate = 2008-03-15|last = Micro AeroDynamics|authorlink = |year = 2003}}</ref> Vortex generators can be found on many devices, but the term is most often used in [[aircraft]] design <ref name="Peppler"/> and for improving [[wind turbine]] performance.<ref name="WindTurbineVortexGenerators">[http://www.upwindsolutions.com/upgrades/wind-turbine-vortex-generator/ Wind Turbine Vortex Generators], UpWind Solutions.</ref>

Vortex generators delay [[flow separation]] and aerodynamic stalling, thereby improving the effectiveness of wings and control surfaces<ref name="MicroHow"/> (e.g., [[Embraer 170]] and [[Symphony SA-160]]). For swept-wing transonic designs, they alleviate potential [[shock-stall]] problems (e.g., [[Hawker Siddeley Harrier|Harrier]], [[Blackburn Buccaneer]], [[Gloster Javelin]]).

==Method of operation==
Vortex generators are most often used to delay [[flow separation]]. To solve this problem, they are often placed on the external surfaces of vehicles <ref name="Clancy">Clancy, L.J. ''Aerodynamics'', Section 5.31</ref> and wind turbine blades. On both aircraft and wind turbine blades they are installed on the front third of a [[wing]] in order to maintain steady airflow over the control surfaces at the trailing edge.<ref name="MicroHow"/> They are typically rectangular or triangular, about 80% as tall as the [[boundary layer]], and run in spanwise lines near the thickest part of the wing.<ref name="Peppler"/> They can be seen on the wings and vertical tails of many [[airliner]]s. Vortex generators are positioned obliquely so that they have an [[angle of attack]] with respect to the local airflow.<ref name="Peppler"/>

A vortex generator creates a tip vortex which draws energetic, rapidly-moving air from outside the slow-moving boundary layer into contact with the surface. The boundary layer normally thickens as it moves along the surface, reducing the effectiveness of trailing-edge control surfaces; vortex generators can be used to remedy this problem, among others, by "re-energizing the boundary layer".<ref name="Peppler"/><ref name="MicroHow"/>

==After-market installation==
Many aircraft carry vane vortex generators from time of manufacture, but there are also after-market suppliers who sell VG kits to improve the [[STOL]] performance of some light aircraft.<ref name="Micro">{{cite web|url = http://www.microaero.com/|title = Micro Vortex Generators for Single and Twin Engine Aircraft|accessdate = 2008-03-15|last = Micro AeroDynamics|authorlink = |year = 2003}}</ref> After-market suppliers claim (i) that VGs lower stall speed and reduce take-off and landing speeds, and (ii) that VGs increase the effectiveness of ailerons, elevators and rudders, thereby improving controllability and safety at low speeds.<ref>{{cite web|url=http://www.landshorter.com/page2.html |title=Land Shorter! Benefits |publisher=Landshorter.com |date=1970-01-01 |accessdate=2012-10-09}}</ref> For home-built and experimental [[homebuilt aircraft|kitplane]]s, VGs are cheap, cost-effective and can be installed quickly; but for certified aircraft installations, [[Type certificate|certification]] costs can be high, making the kits relatively expensive.<ref name="Micro" /><ref name="Busch"/>

Owners fit after-market VGs primarily to gain benefits at low speeds, but a downside is that such VGs may reduce cruise speed slightly. In tests performed on a [[Cessna 182]] and a [[Piper Cherokee|Piper PA-28-235 Cherokee]], independent reviewers have documented a loss of cruise speed of {{convert|1.5|to|2.0|kn|km/h|1|abbr=on}} . However, these losses are relatively minor, since an aircraft wing at high speed has a small angle of attack, thereby reducing VG drag to a minimum.<ref name="Busch"/><ref name="COPAMay2003">Psutka, Kevin, ''Micro-vortex generators'', [[Canadian Owners and Pilots Association|COPA Flight]], August 2003</ref><ref name="COPAJuly2004">Kirkby, Bob, ''Vortex Generators for the Cherokee 235'', [[Canadian Owners and Pilots Association|COPA Flight]], July 2004</ref>

Owners have reported that on the ground, it can be harder to clear snow and ice from wing surfaces with VGs than from a smooth wing, but VGs are not generally prone to in-flight icing as they reside within the boundary layer of airflow. VGs may also have sharp edges which can tear the fabric of airframe covers and may thus require special covers to be made.<ref name="Busch"/><ref name="COPAMay2003" /><ref name="COPAJuly2004" />

For twin-engined aircraft, manufacturers claim that VGs reduce single engine control speed ([[V speeds|Vmca]]), increase zero fuel and gross weight, improve the effectiveness of [[aileron]]s and [[rudder]], provide a smoother ride in turbulence and make the aircraft a more stable instrument platform<ref name="Micro" />

==Increase in maximum takeoff weight==
Many of the vortex generator kits available for light twin-engine airplanes bring with them the added benefit of an increase in [[maximum takeoff weight]].<ref name="Micro"/> This might seem paradoxical because installation of vortex generators does not increase the strength of the wing.

The maximum takeoff weight of a twin-engine airplane is determined by structural requirements and single-engine climb performance requirements (which are lower for a lower stall speed). For many light twin-engine airplanes, the single-engine climb performance requirements determine a lower maximum weight rather than the structural requirements. Consequently, anything that can be done to improve the single-engine-inoperative climb performance will bring about an increase in maximum takeoff weight.<ref name="Busch"/>

In the USA from 1945<ref>USA Civil Air Regulations, Part 3, §3.85a</ref> until 1991,<ref name="FAR23">USA Federal Aviation Regulations, Part 23, §23.67, amendment 23-42, February 4, 1991</ref>
the one-engine-inoperative climb requirement for multi-engine airplanes with a maximum takeoff weight of {{convert|6000|lb|kg|abbr=on}} or less was as follows:
{{quote|All multiengine airplanes having a stalling speed <math>V_{s0}</math> greater than 70 miles per hour shall have a steady rate of climb of at least <math>0.02(V_{s0})^2</math> in feet per minute at an altitude of 5,000 feet with the critical engine inoperative and the remaining engines operating at not more than maximum continuous power, the inoperative propeller in the minimum drag position, landing gear retracted, wing flaps in the most favorable position …}}
where <math>V_{s0}</math> is the [[Stall (flight)|stalling]] speed in the landing configuration in miles per hour.

Installation of vortex generators can usually bring about a slight reduction in stalling speed of an airplane<ref name="Clancy"/> and therefore reduce the required one-engine-inoperative climb performance. The reduced requirement for climb performance allows an increase in maximum takeoff weight, at least up to the maximum weight allowed by structural requirements.<ref name="Busch">{{cite web|url = http://www.avweb.com/news/reviews/182564-1.html|title = Vortex Generators: Band-Aids or Magic?|accessdate = 2008-03-15|last = Busch|first = Mike|authorlink = |date=November 1997}}</ref>

An increase in maximum weight allowed by structural requirements can usually be achieved by specifying a [[maximum zero fuel weight]] or, if a maximum zero fuel weight is already specified as one of the airplane's limitations, by specifying a new higher maximum zero fuel weight.<ref name="Busch"/>

For these reasons, vortex generator kits for many light twin-engine airplanes are accompanied by a reduction in maximum zero fuel weight and an increase in maximum takeoff weight.<ref name="Busch"/>

The one-engine-inoperative rate-of-climb requirement does not apply to single-engine airplanes, so gains in the maximum takeoff weight (based on stall speed or structural considerations) are less significant compared to those for 1945–1991 twins.

After 1991, the airworthiness certification requirements in the USA specify the one-engine-inoperative climb requirement as a gradient independent of stalling speed, so there is less opportunity for vortex generators to increase the maximum takeoff weight of multi-engine airplanes whose certification basis is FAR 23 at amendment 23-42 or later.<ref name="FAR23"/>

==Maximum landing weight==
Because most light twin engined aircraft landing weights are determined by structural considerations and not stall speed, most VG kits only increase the take-off weight available and not the landing weight. In these cases increasing the landing weight requires either structural modifications or else re-testing the aircraft to demonstrate that the certification requirements are still met at the higher landing weight.<ref name="Busch"/>

==References==
{{reflist}}
{{refbegin}}
* Kermode, A.C. (1972), ''Mechanics of Flight'', Chapter 11, page 350 - 8th edition, Pitman Publishing, London ISBN 0-273-31623-0
* Clancy, L.J. (1975), ''Aerodynamics'', Pitman Publishing, London ISBN 0-273-01120-0
{{refend}}

==See also==
{{Commons |Category:Vortex generators (aircraft wings)|Vortex generators}}
*[[Turbulator]]
*[[Boundary layer suction]]
*[[Boundary layer control]]
*[[Circulation control wing]]

{{Aircraft components}}
{{aviation lists}}

[[Category:Aircraft components]]
[[Category:Aerospace engineering]]
[[Category:Aerodynamics]]
[[Category:Aircraft wing design]]
[[Category:Wind turbines]]

[[de:Turbulator]]

Dissipative system - Revision history

en>Daniele Pugliesi: removed Category:Thermodynamics; added Category:Thermodynamic systems using HotCat

en>Headbomb: Undid revision 523982928 by Garuda0001 (talk) book added by COI editor, feel free to re-instate