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Kent Dominic (talk | contribs) Strunk & White: Never use 14 characters when 6 will do. |
→top: restore specific facet of over-broad ambiguous "dynamic" (Strunk's maxim is "omit *needless* words.") |
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{{continuum mechanics|cTopic=fluid}}
'''Viscosity''' is a measure of a [[fluid|fluid's]]
Viscosity quantifies the internal [[friction|frictional force]] between adjacent layers of fluid that are in relative motion.<ref name="Britanica"/> For instance, when a viscous fluid is forced through a tube, it flows more quickly near the tube's center line than near its walls.<ref>{{cite book |url=https://books.google.com/books?id=XOmlecHzmiwC&pg=PA7 |page=7 |title=A Study of Laminar Compressible Viscous Pipe Flow Accelerated by an Axial Body Force, with Application to Magnetogasdynamics |author=E. Dale Martin |publisher=[[NASA]] |year=1961}}</ref> Experiments show that some [[stress (physics)|stress]] (such as a [[pressure]] difference between the two ends of the tube) is needed to sustain the flow. This is because a force is required to overcome the friction between the layers of the fluid which are in relative motion. For a tube with a constant rate of flow, the strength of the compensating force is proportional to the fluid's viscosity.
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:<math>\mu = AT \exp\left(\frac{B}{RT}\right) \left[ 1 + C \exp\left(\frac{D}{RT}\right) \right],</math>
where <math>A</math>, <math>B</math>, <math>C</math>, <math>D</math> are all constants, provides a good fit to experimental data over the entire range of temperatures, while at the same time reducing to the correct Arrhenius form in the low and high temperature limits. This expression, also known as Duouglas-Doremus-Ojovan model
A two-exponential equation for the viscosity can be derived within the Dyre shoving model of supercooled liquids, where the Arrhenius energy barrier is identified with the high-frequency [[shear modulus]] times a characteristic shoving volume.{{sfn|Dyre|Olsen|Christensen|1996|p=2171}}{{sfn | Hecksher | Dyre | 2015 | p=}} Upon specifying the temperature dependence of the shear modulus via thermal expansion and via the repulsive part of the intermolecular potential, another two-exponential equation is retrieved:{{sfn|Krausser|Samwer|Zaccone|2015|p=13762}}
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| pages = 86–96
| doi = 10.1007/s003970000120
| bibcode = 2001AcRhe..40...86C
| s2cid = 94555820
}}
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*{{cite journal|last=Doremus|first=R.H.|date=2002|title=Viscosity of silica|journal=J. Appl. Phys.|volume=92|issue=12 |pages=7619–7629|doi = 10.1063/1.1515132 |bibcode = 2002JAP....92.7619D }}
*{{cite journal|last1=Dyre|first1=J.C.|last2=Olsen|first2=N. B.|last3=Christensen|first3=T.|date=1996|title=Local elastic expansion model for viscous-flow activation energies of glass-forming molecular liquids|journal=Physical Review B|volume=53|issue=5|pages=2171–2174|doi=10.1103/PhysRevB.53.2171|pmid=9983702|bibcode=1996PhRvB..53.2171D|doi-access=free|
*{{cite journal|url=http://www.physics.uq.edu.au/physics_museum/pitchdrop.shtml|title=The pitch drop experiment|first1=R.|last1=Edgeworth|first2=B.J.|last2=Dalton|first3=T.|last3=Parnell|access-date=2009-03-31|journal=European Journal of Physics|date=1984|volume=5|issue=4|pages=198–200|doi=10.1088/0143-0807/5/4/003|bibcode=1984EJPh....5..198E|s2cid=250769509 |archive-date=2013-03-28|archive-url=https://web.archive.org/web/20130328064508/http://www.physics.uq.edu.au/physics_museum/pitchdrop.shtml|url-status=live|url-access=subscription}}
*{{cite book
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