Editing Wind tunnel (section)

===Origins===

English mathematician and physicist [[Isaac Newton]] (1642–1726) displayed a forerunner to the modern wind tunnel in Proposition 36/37 of his book ''[[Philosophiæ Naturalis Principia Mathematica]]''.<ref>{{Cite book |url=https://books.google.com/books?id=Ppv5h4sgAYwC&pg=PA269 |title=Isaac Newton's Natural Philosophy |date=2001 |publisher=MIT Press |isbn=978-0-262-52425-4 |editor-last=Buchwald |editor-first=Jed Z. |series= |location=Cambridge, Mass. |pages=269 |editor-last2=Newton |editor-first2=Isaac}}</ref><ref>{{Cite book |last=Rowlands |first=Peter |url=https://books.google.com/books?id=u0NBDwAAQBAJ&pg=PA152 |title=Newton – Innovation And Controversy |publisher=[[World Scientific Publishing]] |year=2017 |isbn=9781786344045 |pages=152–153}}</ref>

English military engineer and mathematician [[Benjamin Robins]] (1707&ndash;1751) invented a [[whirling arm]] apparatus to determine drag<ref>{{cite book |editor=Wilson, James |title=Mathematical Tracts of the late Benjamin Robins, Esq |location=London |publisher=J. Nourse |date=1761 |volume=1 |chapter=An account of the experiments, relating to the resistance of the air, exhibited at different times before the Royal Society, in the year 1746 |chapter-url=https://books.google.com/books?id=ha82AAAAMAAJ&pg=PA202}}</ref> and did some of the first experiments in aerodynamics.

[[Sir George Cayley]] (1773–1857) also used a whirling arm to measure the drag and lift of various airfoils.<ref>{{Cite journal|author=J. A. D. Ackroyd|year=2011|title=Sir George Cayley: The Invention of the Aeroplane near Scarborough at the Time of Trafalgar|journal=Journal of Aeronautical History|volume=1|pages=130–81 |url=http://aerosociety.com/Assets/Docs/Publications/The%20Journal%20of%20Aeronautical%20History/2011-06Cayley-Ackroyd2.pdf |archive-url=https://web.archive.org/web/20131226050808/http://aerosociety.com/Assets/Docs/Publications/The%20Journal%20of%20Aeronautical%20History/2011-06Cayley-Ackroyd2.pdf |archive-date=2013-12-26 |url-status=live}}</ref> His whirling arm was {{convert|5|ft|m}} long and attained speeds between 10 and 20 feet per second (3 to 6&nbsp;m/s).

[[Otto Lilienthal]] used a rotating arm to make measurements on wing airfoils with varying [[angle of attack|angles of attack]], establishing their [[lift-to-drag ratio]] polar diagrams, but was lacking the notions of [[induced drag]] and [[Reynolds numbers]].<ref>{{cite news |url= https://leehamnews.com/2017/10/27/bjorns-corner-aircraft-drag-reduction-part-2/ |title= Bjorn's Corner: Aircraft drag reduction, Part 2 |author= Bjorn Fehrm |date= 27 October 2017 |work= Leeham}}</ref>

[[File:Wright Brothers Wind Tunnel Replica.jpg|thumb|Replica of the Wright brothers' wind tunnel]]

Drawbacks of whirling arm tests are that they do not produce a reliable flow of air. Centrifugal forces and the fact that the object is moving in its own wake also mean that detailed examination of the airflow is difficult. [[Francis Herbert Wenham]] (1824–1908), a Council Member of the [[Aeronautical Society of Great Britain]], addressed these issues by inventing, designing, and operating the first enclosed wind tunnel in 1871.<ref>{{cite book |title=A Dictionary of Aviation |first=David W. |last=Wragg |isbn=9780850451634 |edition=first |publisher=Osprey |year=1973 |page=281}}</ref><ref>Note:
* That Wenham and Browning were attempting to build a wind tunnel is briefly mentioned in:  ''Sixth Annual Report of the Aeronautical Society of Great Britain for the Year 1871'', p. 6. [https://babel.hathitrust.org/cgi/pt?id=uc1.b4513625;view=1up;seq=444 From p. 6:]  "For this purpose [viz, accumulating experimental knowledge about the effects of wind pressure], the Society itself, through Mr. Wenham, had directed a machine to be constructed by Mr. Browning, who, he was sure, would take great interest in the work, and would give to it all the time and attention required."
* In 1872, the wind tunnel was demonstrated to the Aeronautical Society.  See:  ''Seventh Annual Report of the Aeronautical Society of Great Britain for the Year 1872'', [https://babel.hathitrust.org/cgi/pt?id=uc1.b4513626;view=1up;seq=10 pp. 6–12.]</ref> Once this breakthrough had been achieved, detailed technical data was rapidly extracted by the use of this tool. Wenham and his colleague John Browning are credited with many fundamental discoveries, including the measurement of l/d ratios, and the revelation of the beneficial effects of a high [[Aspect ratio (wing)|aspect ratio]].

[[Konstantin Tsiolkovsky]] built an open-section wind tunnel with a centrifugal blower in 1897, and determined the [[drag coefficient]]s of flat plates, cylinders, and spheres.

Danish inventor [[Poul la Cour]] used wind tunnels to develop [[wind turbine]]s in the early 1890s.
[[Carl Rickard Nyberg]] used a wind tunnel to design his ''[[Flugan]]'' starting in 1897.

The Englishman [[Osborne Reynolds]] (1842–1912) of the [[University of Manchester]] demonstrated that the airflow pattern over a scale model would be the same for the full-scale vehicle if a certain flow parameter were the same in both cases. This parameter, now known as the [[Reynolds number]], is used in the description of all fluid-flow situations, including the shape of flow patterns, the effectiveness of heat transfers, and the onset of turbulence. This comprises the central scientific justification for the use of models in wind tunnels to simulate real-life phenomena.

The [[Wright brothers]]' use of a simple wind tunnel in 1901 to study the effects of airflow over various shapes while developing their [[Wright Flyer]] was in some ways revolutionary.<ref name=Dodson>{{cite journal |author1=Dodson, MG |title=An Historical and Applied Aerodynamic Study of the Wright Brothers' Wind Tunnel Test Program and Application to Successful Manned Flight |website=Defence Technical Information Center |date=2005 |url=https://apps.dtic.mil/sti/citations/ADA437187}}</ref> However, they were using the accepted technology of the day, though this was not yet a common technology in America.

In [[France]], [[Gustave Eiffel]] (1832–1923) built his first open-return wind tunnel in 1909, powered by a {{cvt|50|kW|hp|order=flip}} electric motor, at Champs-de-Mars, near the foot of the tower that bears his name.

Between 1909 and 1912 Eiffel ran about 4,000 tests in his wind tunnel, and his systematic experimentation set new standards for aeronautical research.
In 1912 [[Laboratoire Aerodynamique Eiffel|Eiffel's laboratory]] was moved to Auteuil, a suburb of Paris, where his wind tunnel with a {{convert|2|m|ft|order=flip|adj=on|sigfig=1}} test section is still operational today.<ref>{{cite web | url=https://www.aerodynamiqueeiffel.fr/ |title = Laboratoire Aerodynamique Eiffel}}</ref> Eiffel significantly improved the efficiency of the open-return wind tunnel by enclosing the test section in a chamber, designing a flared inlet with a honeycomb flow straightener, and adding a diffuser between the test section and the fan located at the downstream end of the diffuser; this was an arrangement followed by a number of wind tunnels later built; in fact the open-return low-speed wind tunnel is often called the Eiffel-type wind tunnel.