Non-Newtonian fluid 1

Non-Newtonian fluid

Continuum mechanics

A non-Newtonian fluid is a fluid whose flow properties differ in any way from those of Newtonian fluids. Mostcommonly the viscosity (measure of a fluid's ability to resist gradual deformation by shear or tensile stresses) ofnon-Newtonian fluids is dependent on shear rate or shear rate history. However, there are some non-Newtonianfluids with shear-independent viscosity, that nonetheless exhibit normal stress-differences or other non-Newtonianbehaviour. Many salt solutions and molten polymers are non-Newtonian fluids, as are many commonly foundsubstances such as ketchup, custard, toothpaste, starch suspensions, paint, blood, and shampoo. In a Newtonian fluid,the relation between the shear stress and the shear rate is linear, passing through the origin, the constant ofproportionality being the coefficient of viscosity. In a non-Newtonian fluid, the relation between the shear stress andthe shear rate is different, and can even be time-dependent. Therefore, a constant coefficient of viscosity cannot bedefined.Although the concept of viscosity is commonly used in fluid mechanics to characterize the shear properties of afluid, it can be inadequate to describe non-Newtonian fluids. They are best studied through several other rheologicalproperties which relate stress and strain rate tensors under many different flow conditions, such as oscillatory shear,or extensional flow which are measured using different devices or rheometers. The properties are better studied usingtensor-valued constitutive equations, which are common in the field of continuum mechanics.

Non-Newtonian fluid 2

Types of non-Newtonian behaviour

Summary

Comparison of non-Newtonian, Newtonian, and viscoelastic properties

Viscoelastic Kelvin material "Parallel" linearsticcombination of elastic andviscous effects[1]

Some lubricants, whipped cream

Thixotropic Apparent viscositydecreases with duration ofstress[2]

Yogurt, xanthan gum solutions, aqueous iron oxide gels, gelatin gels, pectingels, synovial fluid, hydrogenated castor oil, some clays (including bentonite,and montmorillonite), carbon black suspension in molten tire rubber, somedrilling muds, many paints, many floc suspensions, many colloidalsuspensions

Time-independentviscosity

Shear thickening(dilatant)

Apparent viscosityincreases with increasedstress[3]

Suspensions of corn starch in water, sand in water, Silly Putty

Shear thinning(pseudoplastic)

Apparent viscositydecreases with increasedstress[4][5]

Nail polish, whipped cream, ketchup, molasses, syrups, paper pulp in water,latex paint, ice, blood, some silicone oils, some silicone coatings

GeneralizedNewtonian fluids

Viscosity is constantStress depends on normaland shear strain rates andalso the pressure appliedon it

Blood plasma, custard, water

Non-Newtonian fluid 3

Shear thinning fluidA familiar example of the opposite, a shear thinning fluid, or pseudoplastic fluid, is wall paint: one wants the paint toflow readily off the brush when it is being applied to the surface being painted, but not to drip excessively. Note thatall thixotropic fluids are extremely shear thinning, but they are significantly time dependent, whereas the colloquial"shear thinning" fluids respond instantaneously to changes in shear rate. Thus, in order to avoid confusion, the latterclassification is more clearly termed pseudoplastic .

Bingham plasticThere are fluids which have a linear shear stress/shear strain relationship which require a finite yield stress beforethey begin to flow (the plot of shear stress against shear strain does not pass through the origin). These fluids arecalled Bingham plastics. Several examples are clay suspensions, drilling mud, toothpaste, mayonnaise, chocolate,and mustard. The surface of a Bingham plastic can hold peaks when it is still. By contrast Newtonian fluids have flatfeatureless surfaces when still.

RheopecticThere are also fluids whose strain rate is a function of time. Fluids that require a gradually increasing shear stress tomaintain a constant strain rate are referred to as rheopectic. An opposite case of this, is a fluid that thins out withtime and requires a decreasing stress to maintain a constant strain rate (thixotropic).

ExamplesMany common substances exhibit non-Newtonian flows. These include:[6]

• Soap solutions and cosmetics;• Food such as butter, cheese, jam, ketchup, mayonnaise, soup, and yogurt;• Natural substances such as magma, lava, gums, and extracts such as vanilla extract;• Biological fluids such as blood, saliva, semen, and synovial fluid;• Slurries such as cement slurry, emulsions such as mayonnaise, and some kinds of dispersions.

Oobleck

Demonstration of a non-Newtonian fluid atUniversum in Mexico City

An inexpensive, non-toxic example of a non-Newtonian fluid is asuspension of starch (e.g. cornstarch) in water, sometimes called"oobleck" or "ooze" (1 part of water to 1.5–2 parts of corn starch).[8][9]

Uncooked imitation custard, being a suspension of primarily cornflour,has the same properties. The name "oobleck" is derived from the Dr.Seuss book Bartholomew and the Oobleck.

Flubber

Flubber is a non-Newtonian fluid, easily made from polyvinylalcohol–based glues and borax, that flows under low stresses butbreaks under higher stresses and pressures. This combination offluid-like and solid-like properties makes it a Maxwell solid. Itsbehaviour can also be described as being viscoplastic or gelatinous.[10]

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Oobleck on a subwoofer. Applying force tooobleck, by sound waves in this case, makes the

non-Newtonian fluid thicken.[7]

Chilled caramel topping

Another example of this is chilled caramel ice cream topping (so longas it incorporates hydrocolloids such as carrageenan and gellan gum).The sudden application of force —for example by stabbing the surfacewith a finger, or rapidly inverting the container holding it— leads tothe fluid behaving like a solid rather than a liquid. This is the "shearthickening" property of this non-Newtonian fluid. More gentletreatment, such as slowly inserting a spoon, will leave it in its liquidstate. Trying to jerk the spoon back out again, however, will trigger thereturn of the temporary solid state.[11]

Silly Putty

Silly Putty is a silicone polymer based suspension which will flow, bounce, or break depending on strain rate.

KetchupKetchup is a shear thinning fluid.[3][12] Shear thinning means that the fluid viscosity decreases with increasing shearstress. In other words, fluid motion is initially difficult at slow rates of deformation, but will flow more freely at highrates.

Tricks with non-Newtonian fluidsA person moving quickly and applying sufficient force with their feet can walk across certain types ofnon-Newtonian fluid, such as oobleck. People can also put oobleck on a subwoofer to make it thicken and bounce

References[1] Tropea, Alexander L. Yarin, John F. Foss, Publisher: Springer, 9 October 2007, ISBN 3-540-25141-3, ISBN 978-3-540-25141-5, p.676,

Google books (http:/ / books. google. co. uk/ books?id=y0xDUAdQAlkC& lpg=PA669& dq=thixotropic& pg=PA661#v=onepage&q=thixotropic& f=false)

[2] Springer handbook of experimental fluid mechanics, Cameron Tropea, Alexander L. Yarin, John F. Foss, Publisher: Springer, 9 October2007, ISBN 3-540-25141-3, ISBN 978-3-540-25141-5, p.661, Google books (http:/ / books. google. co. uk/ books?id=y0xDUAdQAlkC&lpg=PA669& dq=thixotropic& pg=PA661#v=onepage& q=thixotropic& f=false)

[3] Pump Application Desk Book, 3rd edition, Paul N. Garay, Prentice Hall, August 1996, ISBN 0-88173-231-1, ISBN 978-0-88173-231-3,p.358, Google books (http:/ / books. google. co. uk/ books?id=pww5cxwitHAC& lpg=PP1& dq=0881732311& pg=PA359#v=snippet&q=thixotropic& f=false)

[4] Rheology of Fluid and Semisolid Foods: Principles and Applications, M. A. Rao, Publisher: Springer, 2nd edition, 28 August 2007, ISBN0-387-70929-0, ISBN 978-0-387-70929-1, p.8, Google books (http:/ / books. google. co. uk/ books?id=BLlmimePW18C& lpg=PA33&dq=shear thinning& pg=PA8#v=snippet& q="shear thinning"& f=false)

[5] Emulsions, Foams, and Suspensions: Fundamentals and Applications, Laurier L. Schramm, Publisher: Wiley VCH, 26 July 2005, ISBN3-527-30743-5, ISBN 978-3-527-30743-2p.173, Google books (http:/ / books. google. co. uk/ books?id=qFi61f1NqNIC& lpg=PA173&dq=pseudoplastic& pg=PA173#v=onepage& q=pseudoplastic& f=false)

[7] This demonstration of oobleck is a popular subject for YouTube videos, such as this (http:/ / www. youtube. com/ watch?v=8UwL0ywr7HQ).[8] Oobleck: The Dr. Seuss Science Experiment (http:/ / www. instructables. com/ id/ Oobleck/ )[9] Outrageous Ooze (http:/ / www. exploratorium. edu/ science_explorer/ ooze. html)[10] Glurch Meets Oobleck (http:/ / www. extension. iastate. edu/ e-set/ science_is_here/ glurch. html). Iowa State University Extension.[11] The Rheology of Caramel (http:/ / etheses. nottingham. ac. uk/ 1837/ 1/ Phd_thesis_Giuseppina_Barra. pdf), Giuseppina Barra, Ph.D. thesis,

2004.[12] Microscopy reveals why ketchup squirts (http:/ / www. rsc. org/ chemistryworld/ News/ 2011/ September/ 02091103. asp), Chemistry

World, Sep 2 2011, Royal Society of Chemistry

Non-Newtonian fluid 5

External links• Classical experiments with Non-Newtonian fluids by the National Committee for Fluid Mechanics (https:/ / www.

youtube. com/ watch?v=Ol6bBB3zuGc) on YouTube

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Article Sources and ContributorsNon-Newtonian fluid  Source: http://en.wikipedia.org/w/index.php?oldid=558208047  Contributors: 2602:304:784C:7999:21C:B3FF:FEBB:F225, A13ean, Aboalbiss, Alansohn,AlejandroLinaresGarcia, Alesis69, Alex Bakharev, Altered Walter, Angela, Anr, Arjun01, Arthena, Awickert, B137, BarroColorado, Beefman, BenediktStegmaier, Betacommand, Bingoboard,Bobby122, Boing! said Zebedee, Bongomatic, Bovineone, Bteed, Cadwaladr, Carnildo, CesarB, Cfp, Chadernook, Chariset, Charles Matthews, Chetvorno, Chicocvenancio, Chucklingcanuck,Ciphers, CorbinSimpson, CrazyTerabyte, Crowsnest, Cutler, CyrilleDunant, DARTH SIDIOUS 2, DavidLeighEllis, Dcoetzee, Dee Earley, Dekisugi, Delldot, Devil Master, DhananSekhar,Dhollm, Discospinster, Dolphin51, Doremo, Dougher, Drlight11, Duk, Epbr123, ErinK, Eupedia, Ewulp, FT2, Falcon8765, Favonian, Fcueto, Finemann, Firien, Flowersofnight, Fluzwup,FrancisGM, FrankTobia, Fuzheado, Geeoharee, Giftlite, GilbertoSilvaFan, Gilliam, Giraffedata, GoShow, Goodcaster1, Grey Geezer, Guest9999, Gurch, H Padleckas, HMSSolent, Halogenated,Headbomb, Heron, Hhhippo, Hike395, Hjw13, HorsePunchKid, Hu12, Ingolfson, Italtrav, J. Finkelstein, J.delanoy, Jack Greenmaven, Jan1nad, Jj137, Jjmatt33, Jmjanzen, Jmrowland, JocK,Johnwcowan, Jon Harald Søby, Josve05a, Juliancolton, KSmrq, Kaszeta, Kay Dekker, Kedmond, Keenan Pepper, KnightRider, Kri, Kubigula, Lahiru k, Logan, LouisBB, Lova Falk, M0rphzone,Marie Poise, Mastercampbell, Meco, Msaroff, Myahoo, Mythealias, Narvalesyunicornios, NatalietheCircusFreak, NewEnglandYankee, Nicoguaro, NinjaKid, NorsemanII, Nunh-huh, NunoTavares, Ohnoitsjamie, Omegatron, Onaraighl, Peterlewis, Peyre, Philip Trueman, Pi zza314159, Player No.1, Playerhater4, PnakoticInquisitor, Quiddity, Radagast3, Ranjitsinha0552,RasputinAXP, RattusMaximus, Raven4x4x, Real doing, Reify-tech, Rfsmit, Rich Farmbrough, Robma, Ruakh, SaintSatanist, Salih, Sandycx, Sanoopj, SarekOfVulcan, Sasquatch, Scentoni,Schorvitz, Sci13, Scientific29, Shriram, Shureg, Skylights76, Snakehr3, Sobreira, Some jerk on the Internet, Someguy1221, Storm Rider, TK421, Taxman, Tazzy531, Technick29, The ThingThat Should Not Be, The ed17, TheDragonMaster, Thehelpfulone, Thelmadatter, Tobias Bergemann, Toh, TopDog5450, ToughIQ, Toytoy, Tree Biting Conspiracy, Twin Bird, Unara,Vahokie02, Valthalas, Varlaam, VederJuda, Waldir, Waltpohl, WikiesGhost, Wolfkeeper, YewBowman, Zephalis, Zymatik, 397 anonymous edits

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