Unit-1 Properties of fluids and Pressure Measurements.pptx
1.
2. Unit-1 Properties of fluids and Pressure Measurements
Fluid Mechanics
Fluid Mechanics is the branch of engineering which deals
with the properties and behavior of fluids at rest and in motion.
Hydraulics
Hydraulics is the branch of engineering deals with the
properties and behavior of water.
Definition of Fluid
Fluid can be defined as the substance which can flow with
or without the aid of force
A fluid may be in three form like as liquid (or) a vapour (or) a
gas
3. Unit-1 Properties of fluids and Pressure Measurements
Types of Fluid
Fluids are classified as follows.
1. Ideal (or) perfect fluid
2. A fluid having density only as property is called Ideal fluid . Ideal fluid one
which
has no viscosity, surface tension, cohesion and adhesion etc. Ex. Imaginary fluid
2. Real fluid (or) Practical fluid
A fluid having viscosity, surface tension, cohesion, adhesion and density is
called Real Fluid. Ex; water, air, lubricating oil
3. Newtonian Fluid
A fluid which obeys Newton’s Law of viscosity is called Newtonian fluid. Ex;
Water, Lubricating oil etc.
4. Non – Newtonian Fluid
A fluid which does not obey Newton’s Law of viscosity is called Non-
Newtonian fluid.
Ex; Paints, Plastics etc.
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12. Pascal law
The intensity of pressure of a liquid at rest is always acts normal
to the surface. The intensity of pressure of a fluid at rest, is acting
equally in all directions. This is known as Pascal’s law.
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16. Hydraulic Jack
The hydraulic jack is used to lift heavy loads by the application of a much
smaller force. It is working under Pascal’s law.
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17. Pressure Measurements
1. Manometer 2. Mechanical gauges
Manometer are the pressure measuring instruments based
on the principle of balancing the fluid columns.
Barometer is used to measure the atmospheric pressure.
Piezometer tube is used to measure the low pressure.
Simple U tube manometer is used to measure the pressure
at a point in a static or dynamic fluid. Gauge pressure and
vacuum pressure can be measured.
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21. Pressure Measurements-Manometers
Micro manometer is used for measuring low pressure with high degree of
accuracy. Micro manometer is a modified form of manometer. In this manometer
cross sectional area of one of limb (left limb) is made much larger than (about 100
times) that of the other limb.
Vertical tube micro manometer
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23. 1. A gauge records a pressure of 24.52 kN/m2 vacuum. Compute the
corresponding absolute pressure in i) kN/m2 ii) in meter of water. The
local atmospheric pressure is 0.75 m of Hg. Specific gravity of mercury is 13.6.
Solution:
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24. 2.The pressure of water in a pipe line was measured by means of a Simple
manometer containing mercury. The mercury level in the open tube is 150
mm higher than that of the left tube. The height of water level in the left tube
is 40 mm. Determine the pressure in the pipe i) in m of water ii) kN/m2
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27. Mechanical gauges
Mechanical gauges are one of the direct pressure measuring
instruments. Example the pressure gauges are known as
mechanical gauges.
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28. Mechanical gauges
Bourdons pressure gauge
This gauge used for measuring high pressure. The principle used in this
gauge is an elastic deformation of a metallic tube which is proportional
to the fluid pressure
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29. Mechanical gauges
This gauge is used for measuring low pressure. The principle used in
this gauge is elastic deformation of a thin element called a
diaphragm is proportional to the pressure.
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30. Mechanical gauges
Dead weight pressure Gauges
This gauge is most accurate pressure gauge. This gauge is
direct method of pressure measurement.
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