# Weissenberg effect

> Mediated Wiki article. Canonical URL: https://mediated.wiki/source/Weissenberg_effect
> Markdown URL: https://mediated.wiki/source/Weissenberg_effect.md
> Source: https://en.wikipedia.org/wiki/Weissenberg_effect
> Source revision: 1324647302
> License: Creative Commons Attribution-ShareAlike 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/)

{{short description|Scientific phenomenon}}
[[File:Effet_Weissenberg.jpg|thumb|right|Illustration of the Weissenberg effect on a 2% solution of high molecular weight [polyacrylamide](/source/polyacrylamide)]]
In [fluid dynamics](/source/fluid_dynamics), the '''Weissenberg effect''' is a phenomenon that occurs when a spinning rod is inserted into a [solution](/source/Solution_(chemistry)) of elastic liquid. Instead of being thrown outward, the solution is drawn towards the rod and rises up around it.<ref>{{cite web |url=http://web.mit.edu/nnf/research/phenomena/rodclimbing.html |title = Research }}</ref>  This is a direct consequence of the normal stress that acts like a [hoop stress](/source/Cylinder_stress) around  the rod. 
The effect is a common example of [non-Newtonian fluid](/source/non-Newtonian_fluid) dynamics, which has been shown to occur for polystyrene.<ref>{{cite web |url=https://nnf.mit.edu/home/billboard/topic-5 |title = Article on the Weissenberg effect by Non-Newtonian Fluid Dynamics Group at the Massachusetts Institute of Technology }}</ref>

However, it is not always necessary to insert a rod to observe this effect. A rotating disk at the bottom of a [viscoelastic](/source/viscoelastic) [non-Newtonian fluid](/source/non-Newtonian_fluid) can produce a similar phenomenon: the fluid rises at the center, whereas a [Newtonian fluid](/source/Newtonian_fluid) forms a depression,<ref>
{{cite web
 |title=Abstract: Viscoelastic Flow in Microchannels
 |url=https://absimage.aps.org/image/DFD08/MWS_DFD08-2008-000356.pdf
 |website=APS Division of Fluid Dynamics Meeting Abstracts (DFD08)
 |publisher=American Physical Society
 |date=2008
 |access-date=2025-11-11
 |language=en
 |type=Conference abstract
}}</ref> as seen when stirred with a [magnetic stirrer](/source/magnetic_stirrer). [[File:Magnetic Stirrer.JPG|thumb|right|200px|A [Newtonian fluid](/source/Newtonian_fluid) forming a depression when stirred with a magnetic stirrer.]] The height of the fluid at the center increases with both the rotational speed of the disk and the elasticity of the fluid.<ref>
{{cite web
 |title=Abstract: Viscoelastic Flow in Microchannels
 |url=https://absimage.aps.org/image/DFD08/MWS_DFD08-2008-000356.pdf
 |website=APS Division of Fluid Dynamics Meeting Abstracts (DFD08)
 |publisher=American Physical Society
 |date=2008
 |access-date=2025-11-11
 |language=en
 |type=Conference abstract
}}</ref>
The effect is named after [Karl Weissenberg](/source/Karl_Weissenberg) who published about it in 1947.<ref>{{cite journal |last=Weissenberg |first=K. |date=1947-03-01 |title=A Continuum Theory of Rhelogical Phenomena |url=https://www.nature.com/articles/159310a0 |journal=Nature |language=en |volume=159 |issue=4035 |pages=310–311 |doi=10.1038/159310a0 |pmid=20293529 |bibcode=1947Natur.159..310W |issn=1476-4687 |url-access=subscription }}</ref>

== References ==
{{reflist}}

== External links ==
* [http://www.bsr.org.uk/weissenberg/3/Isolation%20of%20Weissenberg%20Effect.htm The Isolation of, and the Initial Measurements of the Weissenberg Effect]

Category:Viscosity
Category:Rheology

{{non-Newtonian fluids}}

{{fluiddynamics-stub}}

---
Adapted from the Wikipedia article [Weissenberg effect](https://en.wikipedia.org/wiki/Weissenberg_effect) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Weissenberg_effect?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.