en>Monkbot: /* General aviation */Fix CS1 deprecated date parameter errors

2014-01-19T06:29:45Z

General aviation: Fix CS1 deprecated date parameter errors

← Older revision		Revision as of 08:29, 19 January 2014
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	~~Royal Votaw~~ is my title ~~but I~~ by no ~~means truly liked~~ that ~~title~~. ~~Playing crochet~~ is ~~something that I~~'~~ve done~~ for ~~years~~. ~~I presently live in Arizona but now I'm contemplating other choices~~. ~~I am~~ a ~~manufacturing~~ and ~~distribution officer~~.<br><br>~~Here~~ is ~~my weblog~~ [http://~~Portal~~.~~Novarad~~.~~net~~/~~ActivityFeed~~/~~MyProfile~~/~~tabid~~/91/~~UserId~~/~~1043/Default.aspx Portal.Novarad.net~~]		The '''drag divergence Mach number''' (not to be confused with [[critical Mach number]]) is the [[Mach number]] at which the [[Drag (physics)\|aerodynamic drag]] on an [[airfoil]] or [[airframe]] begins to increase rapidly as the Mach number continues to increase.<ref>{{cite book\|last=Anderson\|first=John D.\|title=Fundamentals of Aerodynamics\|publisher=McGraw-Hill\|year=2001\|pages=613}}</ref> This increase can cause the [[drag coefficient]] to rise to more than ten times its [[aerodynamics#low-speed aerodynamics\|low speed]] value.

			The value of the drag divergence Mach number is typically greater than 0.6; therefore it is a [[aerodynamics#transonic aerodynamics\|transonic]] effect. The drag divergence Mach number is usually close to, and always greater than, the [[critical Mach]] number. Generally, the [[drag coefficient]] peaks at Mach 1.0 and begins to decrease again after the transition into the [[aerodynamics#supersonic aerodynamics\|supersonic]] regime above approximately Mach 1.2.

			The large increase in drag is caused by the formation of a [[shock wave]] on the upper surface of the airfoil, which can induce [[flow separation]] and [[adverse pressure gradient]]s on the aft portion of the wing. This effect requires that [[aircraft]] intended to fly at [[supersonic]] speeds have a large amount of [[thrust]]. In early development of [[transonic]] and [[supersonic]] aircraft, a steep dive was often used to provide extra acceleration through the high drag region around Mach 1.0.
			This steep increase in [[drag (physics)\|drag]] gave rise to the popular false notion of an unbreakable [[sound barrier]], because it seemed that no aircraft technology in the foreseeable future would have enough [[aircraft propulsion\|propulsive]] force or [[Aircraft flight control systems\|control]] authority to overcome it. Indeed, one of the popular analytical methods for calculating drag at high speeds, the [[Prandtl-Glauert rule]], predicts an [[infinity\|infinite]] amount of drag at Mach 1.0.

			Two of the important technological advancements that arose out of attempts to conquer the sound barrier were the [[Whitcomb area rule]] and the [[supercritical airfoil]]. A [[supercritical airfoil]] is shaped specifically to make the drag divergence Mach number as high as possible, allowing aircraft to fly with relatively lower drag at high [[Subsonic flight\|subsonic]] and low [[transonic]] speeds. These, along with other advancements including [[computational fluid dynamics]], have been able to reduce the factor of increase in drag to two or three for modern aircraft designs.<ref>{{cite book\|last=Anderson\|first=John D.\|title=Fundamentals of Aerodynamics\|publisher=McGraw-Hill\|year=2001\|pages=615}}</ref>

			Drag divergence Mach numbers for a given family of propeller airfoils can be approximated by Korn's relation:<ref>Boppe, C.W., "CFD Drag Prediction for Aerodynamic Design," Technical Status Review on Drag Prediction and Analysis from Computational Fluid Dynamics: State of the Art, AGARD AR 256, June 1989, pp. 8-1 – 8-27.</ref>

			:<math>M_{dd} + \frac{c_{l,design}}{10} + \frac{t}{c} = K</math>

			Where <math>c_{l,design}</math> is the coefficient of lift of a specific section of the airfoil, <math>t</math> is the airfoil thickness at a given section, and <math>c</math> is the chord length at a given section. <math>K</math> is a factor established through CFD analysis:

			K = 0.87 for conventional airfoils (6 series)<ref>Mason,W.H. [http://www.dept.aoe.vt.edu/~mason/Mason_f/TransonicAeroPres.pdf "Some Transonic Aerodynamics", p. 51.]</ref><br />
			K = 0.95 for supercritical airfoils

			==See also==
			*[[wave drag]]
			*[[supercritical airfoil]]
			*[[critical mach]]
			*[[speed of sound]]
			*[[sound barrier]]

			== Notes ==
			<references />

			[[Category:Aerodynamics]]

110.234.16.49: /* Airliners */

2012-07-18T06:23:18Z

Airliners

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Royal Votaw is my title but I by no means truly liked that title. Playing crochet is something that I've done for years. I presently live in Arizona but now I'm contemplating other choices. I am a manufacturing and distribution officer.<br><br>Here is my weblog [http://Portal.Novarad.net/ActivityFeed/MyProfile/tabid/91/UserId/1043/Default.aspx Portal.Novarad.net]

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en>Monkbot: /* General aviation */Fix CS1 deprecated date parameter errors

110.234.16.49: /* Airliners */