Newtonian and non-Newtonian fluids can be categorized based on their viscosity properties. Newtonian fluids have a constant viscosity regardless of shear stress. Non-Newtonian fluids have viscosities that change with applied shear. Specifically, pseudoplastics become less viscous and dilatants become more viscous under shear. Additional categories include thixotropic fluids, whose viscosity decreases over time under shear, and rheopectic fluids, whose viscosity increases over time under shear. Common examples of each type are provided.

1. NEWTONIAN AND
NON – NEWTONIAN
FLUIDS

2. MUHAMMAD AREEB UL HAQ 15053323-
004
NAJAM ALI 15053323-003
SAMIULLAH 15053323-001
GROUP 1

3. WHAT IS FLUID?
 A fluid is a substance that continually deforms
(flows) under an applied shear stress or in
simpler terms, a fluid is a substance which
cannot resist any shear force applied to it.

4. PROPERTIES OF FLUIDS
 Density
 Viscosity
 Temperature
 Pressure

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

6. EFFECTS OF TEMPERATURE
 The viscosity of liquids decreases with
increase the temperature.
 The viscosity of gases increases with the
increase the temperature.

8. EFFECTS OF PRESSURE
 Lubricants viscosity increases with pressure.
 For most lubricants this effect is considerably
largest than the other effects when the
pressure is significantly above atmospheric.

9. NEWTON’S LAW OF
VISCOSITY
 Newton’s law of viscosity states that “ shear
stress is directly proportional to velocity
gradient ”.
 That is the shear stress between the two
adjacent layers of fluid is directly proportional
to the negative value of the velocity gradient
between the same two adjacent fluid layers.
 (Further mathematically described in
Newtonian fluid topic)

10. TYPES OF VISCOSITY

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

12. NEWTONIAN FLUIDS

13. WHAT ARE NEWTONIAN
FLUIDS?
 Where stress is directly proportional to rate of
strain or Fluid with a constant viscosity at a
fixed temperature and pressure.
 A Newtonian fluid's viscosity remains constant,
no matter the amount of shear applied for a
constant temperature.. These fluids have a
linear relationship between viscosity and shear
stress.

14. Continue…..
 They obey the Newton’s law of viscosity,
which is
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 of proportionality
 du/dy= velocity gradient perpendicular to the
direction of shear.

15. WHAT IS STRAIN AND STRAIN
RATE?
 Strain
 The ratio of extension to original length is
called strain it has no units as it is a ratio of
two lengths measured in meters.
 Strain rate
 is the change in strain (deformation) of a
material with respect to time.

16. WHAT IS STRESS AND SHEAR
RATE?
 Stress
 The stress applied to a material is the force
per unit area applied to the material. The
maximum stress a material can stand before it
breaks is called the breaking stress or ultimate
tensile stress.
 Shear rate
 is the rate at which a progressive shearing
deformation is applied to some material

17. GRAPH OF NEWTONIAN
FLUID

18. Continue…..
 This type of flow behavior Newton assumed
for all fluids is called Newtonian.
 It is, however, only one of several types of flow
behavior you may encounter.
 Graph A shows that the relationship between
shear stress and shear rate is a straight line.
 Graph B shows that the fluid's viscosity
remains constant as the shear rate is varied.
 Typical Newtonian fluids include water and thin
motor oils.

19. EXAMPLES
 Water
 Mineral oil
 Gasoline
 Alcohol

20. NON - NEWTONIAN FLUID

21. WHAT ARE NON NEWTONIAN
FLUIDS?
 Where stress is proportional to rate of strain,
its higher powers and derivatives (basically
everything other than Newtonian fluid).
 Non-Newtonian fluids are the opposite of
Newtonian fluids.
 When shear is applied to non-Newtonian
fluids, the viscosity of the fluid changes.

22. Continue….
 A non-Newtonian fluid is broadly defined as
one for which the relationship is not a
constant.
 It means that there is non-linear relationship
between shear rate & shear stress.
 In other words, when the shear rate is varied,
the shear stress doesn't vary in the same
proportion (or even necessarily in the same
direction).
 E.g. Soap Solutions & cosmetics, Food such
as butter, jam, cheese, soup, yogurt, natural
substances such as lava, gums, etc.

23. THE BEHAVIOR OF THE FLUID
CAN BE DESCRIBED IN FOUR
WAYS.
 Dilatant
 Pseudoplastic
 Thixotropic Fluid
 Rheopectic fluid

24. DILATANT
PSEUDOPLASTIC
TIME INDEPENDENT

25. DILATANT
 Viscosity of the fluid increases when shear is
applied.
 Examples
 Quicksand
 Corn flour
 Starch in water
 Potassium silicate in water.

26. GRAPH

27. Continue…
 Increasing viscosity with an increase in shear
rate characterizes the dilatant fluid.
 Although rarer than pseudo plasticity, dilatancy
is frequently observed in fluids containing high
levels of deflocculated solids, such as clay
slurries, candy compounds and sand/water
mixtures.
 Dilatancy is also referred to as shear-
thickening flow behavior.

28. PSEUDOPLASTIC
 Pseudoplastic is the opposite of dilatant i.e.
the more shear applied, the less viscous it
becomes.
 Example
 Ketchup
 Polymer solutions
 greases
 starch suspensions
 biological fluids, detergent slurries etc.

29. GRAPH

30. Continue…
 This type of fluid will display a decreasing
viscosity with an increasing shear rate.
 Probably the most common of the non-
Newtonian fluids, pseudo-plastics include
paints, emulsions, and dispersions of many
types.
 This type of flow behavior is sometimes called
"shear-thinning.

31. PSEUDOPLASTIC VS
DILATANT

32. THIXOTROPIC FLUID
RHEOPECTIC FLUID
TIME DEPENDENT

33. THIXOTROPIC FLUID
 Fluids with thixotropic properties decrease in
viscosity when shear is applied.
 EXAMPLES
 Inks
 Paints
 Cosmetics
 Asphalt
 Glue
 Drilling muds.

34. GRAPH

35. Continue…
 These fluids exhibit a reversible decrease in
shear stress with time at a constant shear rate.
 Examples
 Some polymer solutions
 Some food materials and paints.

36. RHEOPECTIC
 Rheopectic is very similar to dilatant in that
when shear is applied, viscosity increases.
The difference here, is that viscosity increase
is time-dependent.
 EXAMPLES
 Gypsum paste
 Cream
 Bentonite clay suspensions, certain sols and
clay suspensions.

37. GRAPH

38. Comparison of non-Newtonian, Newtonian, and viscoelastic properties
Viscoelast
ic
Kelvin
material, Maxwell
material
"Parallel" linear
combination of
elastic and
viscous effects[1]
Some lubricants, whipped cream, Silly Putty
Time-
dependent
viscosity
Rheopecty
Apparent
viscosity increas
es with duration
of stress
Synovial fluid, printer ink, gypsum paste
Thixotropic
Apparent
viscosity decreas
es with duration
of stress[1]
Yogurt, xanthan gum solutions,
aqueous iron
oxide gels, gelatin gels, pectin gels, hydroge
nated castor oil,
some clays (including bentonite,
and montmorillonite), carbon
black suspension in molten tire rubber,
some drilling muds, many paints,
many floc suspensions,
many colloidal suspensions
Non
Newtonian
Viscosity
Shear
thickening (dilatant)
Apparent
viscosity increas
es with increased
stress[2]
Suspensions of corn starch in water
Shear
thinning (pseudoplas
tic)
Apparent
viscosity decreas
es with increased
stress[3][4]
Nail polish, whipped
cream, ketchup, molasses, syrups, paper
pulp in water, latex paint, ice, blood,
some silicone oils, some silicone
coatings, sand in water
Generalized
Newtonian fluids
Viscosity is
constant.
Stress depends
on normal and
shear strain rates
and also the
pressure applied
on it
Blood plasma, custard, water

39. RHEOPECTIC VS
THIXOTROPIC

40. GRAPHICALLY DIFFERENCE

41. COLLECTIVE GRAPH

42. THANKS