Viscosity Measurement- Viscosity is measured with various types of viscometers and rheometers. A rheometer is used for those fluids

1. Green University of
Bangladesh
Department of Textile Engineering
Presentation on
Viscosity Measurement
 Presented by
Golam Sarwar: 120103019
Sifath Abdan:120303003
Mizanur Rahman:120103004

2. Viscosity
 Viscosity is the measure of the internal friction of a
fluid.
 This friction becomes apparent when a layer of fluid is
made to move in relation to another layer.
 The greater the friction, the greater the amount of force
required to cause this movement, which is called shear.
 Shearing occurs whenever the fluid is physically moved
or distributed, as in pouring, spreading, spraying,
mixing, etc. Highly viscous fluids, therefore, require
more force to move than less viscous materials.

3. Why should We measure Viscosity?
 From viscosity measurement, we can obtain much useful
behavioral and predictive information for various
products.
 A frequent reason for the measurement of rheological
properties can be found in the area of quality control,
where raw materials must be consistent from batch to
batch.
 For this purpose, flow behavior is an indirect measure of
product consistency and quality.

4. Types of Viscosity

5.  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.

6. Viscosity coefficients
 Viscosity coefficients can be defined in two ways:
1) Dynamic or Absolute viscosity
2) Kinematic Viscosity
 Viscosity is a tensorial quantity that can be decomposed
in different ways into two independent components.
The most usual decomposition yields the following
viscosity coefficients:
1) Shear Viscosity
2) Extensional Viscosity

7. Dynamic Viscosity/ Absolute Viscosity
 Proportionality constant between shear stress and
velocity gradient is often called as “Dynamic
Viscosity / Absolute Viscosity”.
 Reciprocal of Dynamic Viscosity is “Fluidity”.
 Ratio of Shear stress to the velocity gradient of the
fluid is known as Absolute Viscosity.

8. Shear Viscosity
The most important one, often referred to as simply
viscosity, describing the reaction to applied shear
stress; simply put, it is the ratio between the
pressure exerted on the surface of a fluid, in the
lateral or horizontal direction, to the change in
velocity of the fluid as you move down in the fluid
(this is what is referred to as a velocity gradient).

9. Volume Viscosity or Bulk Viscosity
Bulk viscosity becomes important only for such
effects where fluid compressibility is essential.
Examples would include shock waves and sound
propagation.
It appears in the Stokes' law (sound attenuation)
that describes propagation of sound in Newtonian
liquid.

10. Instruments for Measuring Viscosity

11. Measurement of Shear viscosity
 Depends upon dynamics of shear force acting upon fluid
either Newtonian / non- Newtonian.
 Instruments which measures the viscosity are called as
Viscometers. Viscometers only measures under one flow
condition.
 Most popular viscometers to measure shear viscosity are
1. Capillary flow viscometer
2. Circular couette flow viscometer
3. Cone & plate flow viscometer
4. Parallel plate flow viscometer

12. Principle of Viscosity Measurement

13. Capillary Flow Viscometer
Capillary flow viscometers are based on pressure
drop

17. With this as a starting point we can derive the Hagen-
Poiseuille Equation:
Q 
(P)R4
8L
 
(P)R4
8LQ

18. Couette Viscometer

21. Cone & Plate Viscometer

23. Parallel Plate Viscometer

24. Shop Floor Viscometers
 Mainly used in Industrial applications to measure
viscosity of mostly Newtonian types of fluid.
 These viscometers consisting simple & convenient
method for viscosity measurement.
 Most popular shop-floor viscometers :
1. Rotational Viscometer
2. Flow through restriction type Viscometer
3. Flow around type Viscometer

25. Rotational Viscometer (Brook field
Viscometer)
 Determine viscosity by measuring the
resistance on a shaft rotating in the
fluid .
 They are designed to make a direct
measurement of the absolute
Viscosity.
 The theory of operation of a rotational
viscometer is based on the Couette
flow model for fully developed,
steady and laminar flow between two
surfaces, one of which is moving.
 Pointer displacement is directly
proportional to fluid viscosity.

27. Flow through restriction type

28. Flow around obstruction type

29. Viscometer standard table

30. Most popular flow around type Viscometer

32. Measurement of Extensional Viscosity

33. Operating Principle

34. Effect of Temperature
The viscosity of liquids decreases with increase the
temperature.
The viscosity of gases increases with the increase
the temperature.
The lubricant oil viscosity at a specific temperature
can be either calculated from the viscosity -
temperature equation or obtained from the
viscosity-temperature chart.

36. Online Viscosity Measurement

37. Applications
 Selection of lubricants for various purpose.
- we can choose an optimum range of viscosity for engine oil.
- for high load and also for speed operation high viscous
lubricants is required.
 In pumping operation
- for high viscous fluid high power will require.
- for low viscous fluid low power will require.
 In making of blend fuel
- less viscous fuels easy to mix.
 In the operation of coating and printing.

38. Thank You All

39. Any Question

40. References:
 www.Wikipedia.com
 www.scribd.com
 www.slidehare.com
 www.blogger.com