This document discusses Newtonian and non-Newtonian fluid behavior. It defines Newtonian fluids as those whose shear stress is directly proportional to shear rate, while non-Newtonian fluids do not follow this relationship. The document categorizes non-Newtonian fluids as time-independent or time-dependent, with time-independent fluids further divided into shear thinning, dilatant, and visco-plastic and time-dependent fluids exhibiting thixotropic or rheopectic behavior. Examples are given of materials that demonstrate different non-Newtonian behaviors along with diagrams of characteristic flow curves. Rheology is defined as the study of flow and deformation of materials.

1. Rheology Properties &
Newtonian and non-newtonian
behavior of fluids
Presented By
Shakil Ahmed
Al-Amin Robi
Azimur Rahman
Pranjol Mondol
Kakon
Nahidul Islam
Hazrat Ali

2. Two Categories of Flow & Deformation
Newtonian (Newtonian Law of Flow)
“The higher the viscosity of a liquid, the greater is the
force per unit area (shearing stress) required to produce
a certain rate of shear”
Shear – is a stress which is applied parallel or
tangential to a face of a material, as opposed to a normal
stress which is applied perpendicularly.
Shear stress
Measured in (SI unit): pascal
Commonly used symbols: τ
Expressed in other quantities: τ = F / A

3. = shear stress
= viscosity of fluid
dv/dy = shear rate, rate of strain or velocity
gradient
Newtonian fluids
Fluids which obey the Newton's law of viscosity
are called as Newtonian fluids
Newton's law of viscosity is given by
dy
   dv



4. A Newtonian fluid (named for Isaac Newton) is a fluid whose
stress versus rate of strain curve is linear and passes through
the origin. The constant of proportionality is known as the
viscosity.

5. In common terms, this means the fluid continues to
flow, regardless of the forces acting on it. For example,
water is Newtonian, because it continues to exemplify
fluid properties no matter how fast it is stirred or
mixed.
For a Newtonian fluid, the viscosity, by definition,
depends only on temperature and pressure (and also
the chemical composition of the fluid if the fluid is not
a pure substance), not on the forces acting upon it.

6. Examples of Newtonian
fluids
All gases and most liquids which have simpler
molecular formula and low molecular weight such
as
Water
Benzene
ethyl alcohol
CCl4
Hexane
and most solutions of simple molecules are
Newtonian fluids

7. Non-Newtonian
A non-Newtonian fluid is a fluid whose flow properties
are not described by a single constant value of viscosity.
Many polymer solutions and molten polymers are non-
Newtonian fluids, as are many commonly found substances
such as ketchup, starch suspensions, paint, blood and
shampoo.
In a non-Newtonian fluid, the relation between the shear
stress and the strain rate is nonlinear, and can even be time-
dependent. Therefore a constant coefficient of viscosity
cannot be defined.

8. Non-Newtonian
fluids
Fluids which do not obey the Newton's law of
viscosity are called as non-Newtonian fluids
η is the apparent viscosity and is not constant
for non-Newtonian fluids
dy
   dv

9. Pseudoplasti
cs
Flow of pseudoplastics is consistent
with the random coil model of polymer
solutions and melts. At low stress, flow
occurs by random coils moving past
each other w/o coil deformation. At
moderate stress, the coils are deformed
and slip past each other more easily. At
high stress, the coils are distorted as
much as possible and offer low
resistance to flow.

10. Pseudoplastic (Shear thinning)
Foods
• Examples:
•Banana puree
• Orange juice concentrate
• Oyster sauce
Shear
stress
Shear rate

11. Shear Thinning
Behavior
Shear thinning behavior is often a result of:
Orientation of non-spherical particles in the direction of
flow. An example of this phenomenon is the pumping of
fiber slurries
Orientation of polymer chains in the direction of flow and
breaking of polymer chains during flow. An example is
polymer melt extrusion
Deformation of spherical droplets to elliptical droplets in
an emulsion. An industrial application where this
phenomenon can occur is in the production of low fat
margarine
Breaking of particle aggregates in suspensions. An
example would be stirring paint

12. Apparent
Viscosity
If the viscosity is influenced by the shear rate,
it is important to specify that the values are
different from the constant ones of an ideally
viscous fluid. The values obtained are
'apparent viscosity' or 'apparent shear viscosity'
values

13. flow curves for different types of
non- Newtonian fluids

14. Examples of Non-Newtonian
fluids
Generally non-Newtonian fluids are complex
mixtures such as
 slurries
Pastes
Gels
polymer solutions etc

15. Various non-Newtonian
Behaviors
Time-independent:
Time-dependent
Viscoelastic

16. Time-Independent Fluid
Behavior
• Fluids for which the rate of shear at any point
is determined only by the value of the shear
stress at that point at that instant; these fluids
are variously known as “time independent”,
“purely viscous. these fluids may be further
subdivided into three different types:
• Shear-thinning or pseudoplastics
• Visco-plastics
• Shear-thickening or dilatant

17. Time dependent
behaviors

18. Thixotropic
If the apparent viscosity decreases with time
e.g. paints, cream, aqueous iron oxide gels,
some drilling mud's
Result of a break down in the microstructure of
the material as shearing continues
This happens when the sheer is exceeded of a
limit
It leads to non-linear stress-strain behavior

19. Thixotropy in a Cement
Paste

20. Rheopectic
Is the rare property of some non-newtonian
fluids if the apparent viscosity increases with
time
The longer the fluid undergoes shearing force,
the higher its viscosity
 Examples are gypsum pastes and printer inks
Also termed as negative thixotropy

21. Rheopectic behavior in a
saturated polyester

22. Time-Independent Fluid
Behavior
1. Shear thinning or pseudoplastic fluids
A shear-thinning or pseudoplastic substance is
characterized by an apparent viscosity that
decreases with increasing shear rate the rate of
decrease of the apparent viscosity is not the
same for each fluid

23. Non - newtonian
Time independent Time dependent
A EC D F GB
_ _
Rheological curves of Time - Independent and Time – DependentLiquids
++

24. Measuring
viscoelasticity
 broadband viscoelastic spectroscopy (BVS)
resonant ultrasound spectroscopy (RUS)

25. Types of
viscoelasticity
Linear viscoelasticity
o It usually happens when the deformations are
Small
Nonlinear viscoelasticity
o Usually happens when the deformationsare
Large

26. Visco-elastic Fluid
Behavior
A visco-elastic fluid displays both elastic and
viscous properties. A true visco-elastic fluid
gives time dependent behavior
Examples
steel or aluminum
Quartz

27. Some phenomena in viscoelastic
materials are
If the stress is held constant, the strain
increases with time
If the strain is held constant, the stress
decreases with time
During rolling, frictional resistance occurs

28. Rheology Properties Of fluids
Rheo – to flow
logos – science
ology – the study of
Thus, rheology is the science that concerns
with the flow of liquids and deformation of
solids.

29. The study of viscosity is of true liquids, solutions,
dilute and concentrated colloidal systems.
It is involved in the mixing and flow of materials,
their packaging into containers, the pouring from
the bottle, extrusion from a tube or a passage of
the liquid to a syringe needle.
It can affect the patient’s acceptability of the
product, physical stability, biologic availability,
absorption rate of drugs in the gastrointestinal
tract.
It influence the choice of processing
equipments in the pharmaceutical system

30. THANKS ALL FOR LISTENING