Editing Drag coefficient (section)

{{short description|Dimensionless parameter to quantify fluid resistance}}
[[File:14ilf1l.svg|thumb|Drag coefficients in fluids with [[Reynolds number]] approximately 10<sup>4</sup><ref>{{cite book |last=Baker|first=W.E.|title=Explosion Hazards and Evaluation, Volume 5|publisher=Elsevier Science |date=1983 |isbn=978-0-444-59988-9 |url= https://www.elsevier.com/books/explosion-hazards-and-evaluation/baker/978-0-444-42094-7}}</ref><ref>{{cite book |last=AARØNÆS|first=ANTON STADE|title=Dynamic response of pipe rack steel structures to explosion loads|publisher=CHALMERS UNIVERSITY OF TECHNOLOGY |date=2014 |url= http://publications.lib.chalmers.se/records/fulltext/199998/199998.pdf}}</ref> Shapes are depicted with the same projected frontal area]]

In [[fluid dynamics]], the '''drag coefficient''' (commonly denoted as: <math>c_\mathrm{d}</math>, <math>c_x</math> or <math>c_{\rm w}</math>) is a [[dimensionless quantity]] that is used to quantify the [[drag (physics)|drag]] or resistance of an object in a fluid environment, such as air or water. It is used in the [[drag equation]] in which a lower drag coefficient indicates the object will have less [[Aerodynamics|aerodynamic]] or [[Hydrodynamics|hydrodynamic]] drag. The drag coefficient is always associated with a particular surface area.<ref>{{cite book |last1=McCormick |first1=Barnes W. |date=1979 |title=Aerodynamics, Aeronautics, and Flight Mechanics |page=24 |publisher=John Wiley & Sons, Inc. |location=New York |isbn=0-471-03032-5}}</ref>

The drag coefficient of any object comprises the effects of the two basic contributors to [[Fluid dynamics|fluid dynamic]] drag: [[skin friction]] and [[form drag]]. The drag coefficient of a lifting [[airfoil]] or [[hydrofoil]] also includes the effects of [[lift-induced drag]].<ref>{{cite book |last1=Clancy |first1=L. J. |title=Aerodynamics |section=5.18 |isbn=978-0-470-15837-1 |date=1975|publisher=Wiley }}</ref><ref>[[Ira H. Abbott|Abbott, Ira H.]], and Von Doenhoff, Albert E.: ''Theory of Wing Sections''. Sections 1.2 and 1.3</ref> The drag coefficient of a complete structure such as an aircraft also includes the effects of interference drag.<ref>{{cite web |url=http://wright.nasa.gov/airplane/drageq.html |title=Modern Drag Equation |publisher=Wright.nasa.gov |date=2010-03-25 |access-date=2010-12-07 |url-status=live |archive-url=https://web.archive.org/web/20110302020853/http://wright.nasa.gov/airplane/drageq.html |archive-date=2011-03-02 }}</ref><ref>Clancy, L. J.: ''Aerodynamics''. Section 11.17</ref>