Fluid

This article is about the concept in physics. For other uses, see Fluid (disambiguation).
Not to be confused with liquid.
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In physics, a fluid is a liquid, gas, or other material that may continuously move and deform (flow) under an applied shear stress, or external force.[1] They have zero shear modulus, or, in simpler terms, are substances which cannot resist any shear force applied to them.

Although the term fluid generally includes both the liquid and gas phases, its definition varies among branches of science. Definitions of solid vary as well, and depending on field, some substances can have both fluid and solid properties.[2] Non-Newtonian fluids like Silly Putty appear to behave similar to a solid when a sudden force is applied.[3] Substances with a very high viscosity such as pitch appear to behave like a solid (see pitch drop experiment) as well. In particle physics, the concept is extended to include fluidic matters other than liquids or gases.[4] A fluid in medicine or biology refers to any liquid constituent of the body (body fluid),[5][6] whereas "liquid" is not used in this sense. Sometimes liquids given for fluid replacement, either by drinking or by injection, are also called fluids[7] (e.g. "drink plenty of fluids"). In hydraulics, fluid is a term which refers to liquids with certain properties, and is broader than (hydraulic) oils.[8]

  1. ^ "Fluid | Definition, Models, Newtonian Fluids, Non-Newtonian Fluids, & Facts". Encyclopedia Britannica. Retrieved 2 June 2021.
  2. ^ Thayer, Ann (2000). "What's That Stuff? Silly Putty". Chemical & Engineering News. 78 (48). American Chemical Society (published 2000-11-27): 27. doi:10.1021/cen-v078n048.p027. Archived from the original on 2021-05-07.
  3. ^ Kroen, Gretchen Cuda (2012-04-11). "Silly Putty for Potholes". Science. Retrieved 2021-06-23.
  4. ^ Example (in the title): Berdyugin, A. I.; Xu, S. G. (2019-04-12). "Measuring Hall viscosity of graphene's electron fluid". Science. 364 (6436). F. M. D. Pellegrino, R. Krishna Kumar, A. Principi, I. Torre, M. Ben Shalom, T. Taniguchi, K. Watanabe, I. V. Grigorieva, M. Polini, A. K. Geim, D. A. Bandurin: 162–165. arXiv:1806.01606. Bibcode:2019Sci...364..162B. doi:10.1126/science.aau0685. PMID 30819929. S2CID 73477792.
  5. ^ "Fluid (B.1.b.)". Oxford English Dictionary. Vol. IV F–G (1978 reprint ed.). Oxford: Oxford University Press. 1933 [1901]. p. 358. Retrieved 2021-06-22.
  6. ^ "body fluid". Taber's online – Taber's medical dictionary. Archived from the original on 2021-06-21. Retrieved 2021-06-22.
  7. ^ Usage example: Guppy, Michelle P B; Mickan, Sharon M; Del Mar, Chris B (2004-02-28). ""Drink plenty of fluids": a systematic review of evidence for this recommendation in acute respiratory infections". BMJ. 328 (7438): 499–500. doi:10.1136/bmj.38028.627593.BE. PMC 351843. PMID 14988184.
  8. ^ "What is Fluid Power?". National Fluid Power Association. Archived from the original on 2021-06-23. Retrieved 2021-06-23. With hydraulics, the fluid is a liquid (usually oil)