Editing Laminar flow (section)

{{short description|Flow where fluid particles follow smooth paths in layers}}
[[File:Laminar flow profile.gif|thumb|The velocity profile associated with laminar flow resembles a deck of [[playing cards]]. This flow profile of a fluid in a pipe shows the fluid acting in layers that slide over one another.]]

'''Laminar flow''' ({{IPAc-en|ˈ|l|æ|m|ɪ|n|ər}}) is the property of fluid particles in [[fluid dynamics]] to follow smooth paths in layers, with each layer moving smoothly past the adjacent layers with little or no mixing.<ref>Streeter, V.L. (1951-1966) ''Fluid Mechanics'', Section 3.3 (4th edition). McGraw-Hill</ref> At low velocities, the fluid tends to flow without lateral mixing, and adjacent layers slide past one another smoothly. There are no cross-currents perpendicular to the direction of flow, nor [[eddies]] or swirls of fluids.<ref name="Geankoplis, Christie John 2003">{{cite book
 |title       = Transport Processes and Separation Process Principles
 |last        = Geankoplis
 |first       = Christie John
 |year        = 2003
 |publisher   = Prentice Hall Professional Technical Reference
 |isbn        = 978-0-13-101367-4
 |url         = http://www.pearsonhighered.com/educator/product/Transport-Processes-and-Separation-Process-Principles-Includes-Unit-Operations/9780131013674.page
 |url-status     = live
 |archive-url  = https://web.archive.org/web/20150501122109/http://www.pearsonhighered.com/educator/product/Transport-Processes-and-Separation-Process-Principles-Includes-Unit-Operations/9780131013674.page
 |archive-date = 2015-05-01
}}</ref> In laminar flow, the motion of the particles of the fluid is very orderly with particles close to a solid surface moving in straight lines parallel to that surface.<ref>{{cite web
 |url         = http://www.efm.leeds.ac.uk/CIVE/CIVE1400/Section4/laminar_turbulent.htm
 |title       = Real Fluids
 |last1       = Noakes
 |first1      = Cath
 |last2       = Sleigh
 |first2      = Andrew
 |date        = January 2009
 |work        = An Introduction to Fluid Mechanics
 |publisher   = University of Leeds
 |access-date  = 23 November 2010
 |url-status     = dead
 |archive-url  = https://web.archive.org/web/20101021003853/http://www.efm.leeds.ac.uk/CIVE/CIVE1400/Section4/laminar_turbulent.htm
 |archive-date = 21 October 2010
}}</ref>
Laminar flow is a flow regime characterized by high [[momentum diffusion]] and low momentum [[convection]].

When a fluid is flowing through a closed channel such as a pipe or between two flat plates, either of two types of flow may occur depending on the velocity and [[viscosity]] of the fluid: laminar flow or [[Turbulence|turbulent flow]]. Laminar flow occurs at lower velocities, below a threshold at which the flow becomes turbulent. The threshold velocity is determined by a dimensionless parameter characterizing the flow called the [[Reynolds number]], which also depends on the viscosity and density of the fluid and dimensions of the channel. Turbulent flow is a less orderly flow regime that is characterized by [[eddies]] or small packets of fluid particles, which result in lateral mixing.<ref name="Geankoplis, Christie John 2003"/> In non-scientific terms, laminar flow is ''smooth'', while turbulent flow is ''rough''.