An introduction to viscometry

1. M. SAUD KHALID (16103123 -036)
MOIZ KHALIL (16103123-007)
Elementary Viscometry

2. Contents
 Introduction
 Viscometry
 Types Of Viscometer
 Applications

3. Elementary Viscometry
 Viscometry deals with the measurement of viscosity of a fluid by
using device called Viscometer.
• AViscometerisaninstrumentusedtomeasurethevisvosityof afluid.
• Itis also known as Viscosimeter.
• Viscometersonly measure under oneflowcondition.
• In elementary viscometry, there are two main types of
viscometers; rotary instruments and tabular capillary
viscometers.

4. Elementary Viscometry
 The basic principle of all viscometers is to provide as simple flow kinematics
as possible, preferably one-dimensional (isometric) flow, in order to determine
the shear strain rate accurately, easily, and independent of fluid type.
 When dealing with Non-Newtonian fluids, it is desireable to use the
voscometer with measure the whole sample under same shear rate .
 Cone and plate viscometers is best to measure the viscosity. In this method,
flow generated has ideally a non-zero velocity component, causing shearing in
one direction thus viscous forces must be dominant but inertial effects should
be negligible.

5. Viscosity
 Viscosity is a measure of the resistance of a fluid to deform under shear stress.
It is commonly perceived as flow behaviour or resistance to pouring. Viscosity
describes a fluids internal resistance to flow and may be thought of as a
measure of fluid friction.

6. Newtonian Fluids:
In Newtonian fluid viscosity remains constant no matter how much shear
stress is applied. For example Water,Mineral oil,Alcohol
Non-Newtonian Fluids:
When the shear stress applied on the fluid its viscosity changes. The
behavior of these fluid can be explained by these four properties
Dilatant
 Pseudo plastic
 Rheopectic
 Thixotropic

7. Viscosity
09:44
Non-Newtonian vs. Newtonian Fluid

8. Elementary Viscometry
 When dealing with Non-Newtonian fluids, it is desireable to use the
voscometer with measure the whole sample under same shear rate .
 Cone and plate viscometer is best to measure the viscosity.
In this method, flow generated has ideally a non-zero velocity
component, causing shearing in one direction thus viscous forces must
be dominant but inertial effects should be negligible.[1]

11. Couple of forces acting on
it is denoted by C. solving
area and inetegrating C,
we get the shear stress.
The apparent viscosity is
given by eq. 3.4

12. Viscometers
Cone-on-plate viscometer

13. Viscometers
Rotating cylinder viscometer

14. • Rotationalviscometer
gathersdata on amaterial’s
viscositybehavior under
differentconditions.
• Rotationalviscometerscan
be used fortheaccurate
measurementof viscosity
forboth Newtonian and
non-Newtonian fluids.

15. Falling Space Viscometers
 The falling ball viscometer is based on Stokes’Law.
 This type of viscometer consists of a circular cylinder filled by the liquid
under investigation.
 A standard ball is allowed to fall down this tube over a calibrated distance
of 100 mm.
• Stokes'lawcanbeusedtocalculatetheviscosityofthefluid. A series ofsteelballbearings
ofdifferentdiameterare normallyused in theclassicexperiment toimprovethe accuracy
ofthecalculation.
 GeorgeGabrielStokesderivedanexpressionforthefrictionalforce exertedonspherical
objectswithverysmallReynoldsnumbersina continuous viscousfluidbychanging the
smallfluid-masslimitof thegenerallyunsolvableNavier-Stokesequations

16.  .
1 = ferromagnetic ball,
2 = electrical magnet
, 3 = magnetic switch,
4 = liquid,
5 = container
where:
Fis thefrictionalforce,
ristheradiusofthesphericalobject, is the
fluidviscosity,and
is theparticle'svelocity.

17. 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.

18. References
 Chapter #3, Fluid flow for chemical and process engineers by F.A. Holland
and R. Bragg,

19.  Thanksforgivingsuchchance
topresentsour idea.