Types of fluids

Types of fluids based on the Newton's law of viscosity.

1. NEWTONIAN AND NON –NEWTONIAN
FLUIDS
By,
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2. WHAT ISFLUID?
Afluidisasubstancethatcontinuallydeforms
(flows)underanappliedshearstressorin
simplerterms,afluidisasubstancewhich
cannotresistanyshearforceappliedtoit.

3. PROPERTIES OFFLUIDS
Density
Viscosity
Temperature
Pressure

4. VISCOSITY
Viscosityisaquantitativemeasureofafluid’s
resistance toflow.
It is defined as the internal friction offluid.
Lack of slipperiness is called asviscosity.
Dynamic (or Absolute)Viscosity:
The dynamic viscosity(η) of a fluid is a measure of
the resistance it offers to relative shearingmotion.


η= F/[A×(u/h)]
η=τ/(u/h)N-s/m²

5. EFFECTS OFTEMPERATURE
Theviscosityofliquidsdecreaseswith
increasethetemperature.
Theviscosityofgasesincreaseswiththe
increase thetemperature.

6. EFFECTS OFPRESSURE
Lubricantsviscosityincreaseswithpressure.
Formostlubricantsthiseffectisconsiderably
largestthantheothereffectswhenthe
pressureissignificantlyaboveatmospheric.

7. NEWTON’S LAW OF
VISCOSITY
Newton’slawofviscositystatesthat“shear
stressisdirectlyproportionaltovelocity
gradient”.
Thatistheshearstressbetweenthetwo
adjacentlayersoffluidisdirectlyproportional
tothenegativevalueofthevelocitygradient
betweenthesametwoadjacentfluidlayers.
(Furthermathematicallydescribedin
Newtonianfluidtopic)

8. Continue…..
TheyobeytheNewton’slawof viscosity,
whichis
τ=µdu/dy
The constant of proportionality is known as the
viscosity.
τ = shear stress exerted by the fluid("drag")
μ = fluid viscosity -a constant ofproportionality
du/dy=velocitygradientperpendiculartothe
direction ofshear.

11. WHAT IS STRESS ANDSHEAR
RATE?
Stress
Thestressappliedtoamaterialistheforce
perunitareaappliedtothematerial.The
maximumstressamaterialcanstandbeforeit
breaksiscalledthebreakingstressorultimate
tensilestress.
Shearrate
istherateatwhichaprogressiveshearing
deformationisappliedtosomematerial

13. WHAT IS STRAIN ANDSTRAIN
RATE?
Strain
Theratioofextensiontooriginallengthis
calledstrainithasnounitsasitisaratioof
twolengthsmeasuredinmeters.
Strainrate
isthechangeinstrain(deformation)ofa
materialwithrespecttotime.

15. Newtonian fluids And
Non -Newtonianfluids
TWO BASIC TYPES OF FLUIDS
REGARDING THIER VISCOSITY
BEHAVIOUR

16. NEWTONIANFLUIDS

17. WHAT ARENEWTONIAN
FLUIDS?
Wherestressisdirectlyproportionaltorateof
strainorFluidwithaconstantviscosityata
fixedtemperatureandpressure.
ANewtonianfluid'sviscosityremainsconstant,
nomattertheamountofshearappliedfora
constanttemperature..Thesefluidshavea
linearrelationshipbetweenviscosityandshear
stress.

19. GRAPH OFNEWTONIAN
FLUID

20. EXAMPLES
Water
Mineraloil
Gasoline
Alcohol

21. NON -NEWTONIANFLUID

22. Bingam plastic
Fluid
A Bingham plastic is a material that behaves as a rigid body at
low stresses but flows as a viscous fluid at high stress. It is
named after Eugene C. Bingham who proposed its mathematical
form.

24. THE BEHAVIOR OF THEFLUID
CAN BE DESCRIBED IN FOUR
WAYS.
Dilatant
Pseudoplastic
ThixotropicFluid
Rheopecticfluid

25. DILATANT
PSEUDOPLASTIC
TIMEINDEPENDENT

26. DILATANT
Viscosity ofthefluidincreases when shear is
applied.
Examples
Quicksand
Cornflour
Starch inwater
Potassium silicate inwater.

28. GRAPH

29. PSEUDOPLASTIC
Pseudoplasticistheoppositeofdilatanti.e.
themoreshearapplied,thelessviscousit
becomes.
Example
Ketchup
Polymersolutions
greases
starchsuspensions
biologicalfluids,detergentslurriesetc.

31. GRAPH

32. PSEUDOPLASTIC VS
DILATANT

33. THIXOTROPICFLUID
RHEOPECTICFLUID
TIMEDEPENDENT

34. THIXOTROPICFLUID
Fluidswiththixotropicpropertiesdecreasein
viscosity when shear isapplied.
EXAMPLES
Inks
Paints
Cosmetics
Asphalt
Glue
Drillingmuds.

36. GRAPH

37. RHEOPECTIC
Rheopecticisverysimilartodilatantinthat
whenshearisapplied,viscosityincreases.
Thedifferencehere,isthatviscosityincrease
istime-dependent.
EXAMPLES
Gypsumpaste
Cream
Bentoniteclaysuspensions,certainsolsand
claysuspensions.

39. GRAPH

40. RHEOPECTICVS
THIXOTROPIC

41. GRAPHICALLYDIFFERENCE

42. COLLECTIVEGRAPH

43. Find the Pseudoplastic Fluid