Viscosity is a measure of a fluid's resistance to flow. There are several types of viscometers used to measure viscosity, including capillary viscometers, falling piston viscometers, rotational viscometers like cone and plate or coaxial cylindrical viscometers, falling ball viscometers, and vibrational viscometers. Rotational viscometers work by measuring the torque required to turn a spindle in the fluid, while other viscometers measure properties like the time for a fluid to pass through a capillary or for a ball to fall through the fluid.

1. VISCOSITY

2. PRESENTED BY : YUMNA SAEED
PHARM-D 1ST PROF.
D18M11
PUNJAB UNIVERSITY COLLEGE OF
PHARMACY
UNIVERSITY OF THE PUNJAB, LAHORE

3. OUTLINE
• INTRODUCTION
• TYPES OF VISCOSITY
• VISCOMETER
• TYPES OF VISCOMETER

4. INTRODUCTION
• Etymology
The word “VISCOSITY” is
derived from the Latin
“VISCOUM”, meaning “
MISTLETOE” and also
“VISCOUS GLUE” made from
mistletoe berries.

5. DEFINITION
• Viscosity of fluid is measure
of it’s resistance to gradual
deformation by shear street/
Tensil stress.
• Also known as internal
friction of a moving fluid.

6. • Shear stress is the force per unit area
required to move one layer of fluid in relation
to another.
• Shear rate is the measure of the change in
speed at which intermediate layers move
with respect to one another.

8. MATHEMATICA
L,
Viscosity= shearing stress/velocity
gradient
Or

9. UNITS
•SI UNIT
PASCAL SEC
•COMMONN UNIT
DYNE S/CM = POISE

10. TYPES OF VISCOSITY
There are Two types of viscosity as,
1.Dymanic viscosity
2.Kinematic viscosity

11. DYNAMIC VISCOSITY
• Dynamic viscosity is the relationship between the shear
stress and the shear rate in a fluid.
• Also known as “ABSOLUTE VISCOSITY”
• “Dynamic viscosity measures the ratio of the
shear stress to the shear rate for a fluid.”
• Mathematical;
μ=​γ/τ

12. 2.KINEMATICS VISCOSITY
• The Kinematic viscosity is the relationship between
viscous and inertial forces in a fluid.
• “Kinematic viscosity measures the ratio of the
viscous force to the inertial force on the fluid.”
• This is shown in the equation below, which may also be
used to convert between dynamic and kinematic viscosity
provided the density of the fluid is known.
• Kinematic viscosity is analogous to diffusivity of mass and
heat, being the diffusivity of momentum.
• Mathematical;
ν=​ρ/μ

14. COMMON UNITS

15. VISCOMETER
• Viscometers are used to measure viscosity in most
circumstances.
• Also known as “VISCOSIMETER.”
• They work for fluids whose viscosity does not
change under varying flow conditions.
• The measure of the resistance is taken by
measuring the drag resistance during relative
motion Through the fluid.

16. RHEOMETER
• RHEOMETERS MUST BE USED WHEN THE VISCOSITY
DOES CHANGE WITH FLOW CONDITION.

17. TYPES OF VISCOMETER
There are several types of viscometers available, some for use
in laboratories and others used as portable viscosity testers.
1. Orifice viscometers
2. Capillary viscometers
3. Falling piston viscometers
4. Rotational viscometers
5. Falling ball viscometers
6. Vibrational viscometers

18. • An orifice viscometer usually consists of a
cup with a hole, through which the fluid
flows.
• Viscosity is determined by timing how
long it takes the cup to empty, and is
measured in cup seconds.
• Orifice viscometers are easy to use
manually, thanks to the fact that they’re
simply dipped into the fluid being worked
with — making them popular in painting
industries. They include Zahn Cups, Ford
Cups, and more.
1.Orifice viscometer

19. • Also known as U-tube viscometers, capillary viscometers
include the Ostwald and Ubbelohde variations.
• They’re straight-forward and simple to use, consisting of a
U-shaped glass tube with two bulbs (one higher and one
lower).
• Fluid passes from the higher bulb to the lower bulb through
a capillary, and viscosity is measured by timing how long it
takes the fluid to pass through the tube.
2.Capillary viscometers

20. Ubbelohde viscometer

21. • According to Wikipedia, falling piston
viscometers were invented by Austin
Norcross, which is why they’re also
called Norcross viscometers.
• They function by drawing the fluid being
measured into the piston cylinder while
the piston is raised; the time it takes the
piston to fall (time-of-fall seconds) due to
the resistance of the fluid is used to
determine viscosity.
• Falling piston viscometers are easy to
use and simple to maintain, and offer
long product life.
3.Falling piston viscometers

22. • Rotational viscometers measure viscosity by immersing a
rotating spindle in the fluid to be tested.
• The amount of power (torque) required to turn the spindle
indicates the viscosity of the fluid, and because rotational
viscometers do not use gravity to function, their
measurements are based on the fluid's internal shear
stress.
4.Rotationalviscometers

23. TYPES OF ROTATIONAL VISCOMETERS
1.CONE AND PLAT VISCOMETER
2.COAXIAL CYLINDERICAL VISCOMETER

24. 1.CONE AND PLATE VISCOMETER
• A cone-plate viscometer is precise torque meter
which driven at discrete rotational speeds.
• The torque measuring system,which consists of
calibrated beryllium-copper spring connecting the
driven mechanism to rotating cone, sense of
resistance to rotation caused by presence of sample
fluid b/w the cone and stationary flat plate.
• The resistance of rotation of the cone produce on
torque that is proportional to shear street in the fluid.
• Readings is easily converted to absolute centipoise

25. A CROSS SECTIONAL VIEW OF A CONE AND
PLATE VISCOMETER.

27. 2.COAXIAL CYLINDERICAL VISCOMETER
• A coaxial cylinder viscometer is
described for the absolute
measurement of shearing stress vs.
velocity gradient up to high values of
gradient.
• Principal features of construction are:
bottomless cylindrical shearing
surfaces, very small annular
clearance, rigid mechanical alignment
of the cylinders, and a pressure-
feeding system.

28. A schematic coaxial cylinderical viscometer

29. • This type of viscometer relies on the terminal velocity achieved by a
balling falling through the viscous liquid whose viscosity is being
measured.
• A sphere is the simplest object to be used because its velocity can
be determined by rearranging Stoke's law*,where r is the sphere’s
radius, η the dynamic viscosity, vthe terminal velocity of the sphere,
σ the density of the sphere, ρ the density of the liquid, and g the
gravitational constant.
5.Falling ball viscometers
OR

30. A typical falling ball viscometric apparatus is shown as
The time taken for the falling ball to pass from
mark 1 to mark 2 is used to obtain viscosity
measurements.

31. • Vibrational viscometers use a
powered vibrating rod to measure
viscosity.
• Different fluids are more or less
resistant to vibrations depending on
how viscous they are.
• Therefore, by measuring the
dampening of the vibration, or by
measuring how quickly the vibration of
the viscometer degrades, viscosity
can be determined.
• Vibrational viscometers are very
popular thanks to the fact that they
offer high sensitivity with no moving .
6.Vibrational viscometers
A resonator produces vibrations in the liquid whose
viscosity is to be tested. An external sensor detects
the vibrations with time, characterizing the material’s
viscosity in realtime.