2. 2
Introduction to fluid
Fluids are divided into liquids and gases.
In general, liquids are called incompressible fluids and gases
compressible fluids.
4. 4
Pressure
Atmospheric pressure is the mass of air surround the Earth.
It changes rapidly every time. Pressure at one area is
defined by the weight of the air above that area.
9. 9
Water Pressure
Pressure is the force that pushes water through pipes.
The pressure is measured in ‘bars’, and one bar of pressure
is required to lift water by 10 meters.
11. 11
Water Pressure
Water pressure does not remain constant and can vary
when demand for water is high. For example, during busy
morning and evening periods, water pressure in the mains
network may reduce.
Low pressure can occur when the pressure in the water main
is not enough
12. 12
Water Pressure
Water pressure is measured at the point where it leaves our
pipework.
All water companies are legally required to supply a
minimum water pressure of 0.7 bar to the point that their
pipework meets the homeowner's supply pipe.
13. 13
Water Pressure
only way to formally measure your water pressure is by
using a water pressure gauge
14. 14
Water Pressure
Water pressure can vary at different times of the day.
Pressure is normally higher late at night when very little
water is being taken from our network and most people's
taps are turned off.
In the morning when people are taking a bath or shower, or
watering their garden on a hot evening, there is a bigger
demand for water which can cause low pressures.
15. 15
Fluid Pressure
water is a fluid that its shape is
changed depend on the container.
Pressure can be determined by the
total amount of vertically water weight
on a specific area.
21. 21
Archimedes principle
The greatest mathematician, physicist
and engineer in ancient Greece.
Discoverer of the famous ‘Principle of
Archimedes.
research in solid and fluid dynamics as
well as on the lever, the centre of
gravity and buoyancy
(287 BC – 212 BC)
22. 22
Archimedes principle- King’s crown problem
King asked his person to make a crown for him.
He want to make sure it is pure gold.
He worried he was cheated.
27. 27
Archimedes principleKing’s crown problem
First he did not know how to solve King’s problem.
Then he felt he would be sentenced then.
He did not know how to measure the volume of crown well.
34. 34
Archimedes principle
Example
A person has a mass of 75kg in air and an apparent
mass of 2kg when submerged in water. Calculate the
volume and density of the person.
35. 35
Archimedes principle
Example
Calculate the apparent mass of an object that has
mass of 5.7kg in air when submerged in vegetable oil
with density of 92g/cm3 if the displaced oil is
16.30cm3.
36. 36
Archimedes principle
Fluid pressure acts all over the wetted surface of a body
floating in a fluid, and the resultant pressure acts in a
vertical upward direction.
This force is called buoyancy. The buoyancy of air is small
compared with the gravitational force of the immersed body,
so it is normally ignored.
38. 38
Archimedes principle
The pressure acting on the cube due to the liquid in the
horizontal direction is balanced right and left.
For the vertical direction, where the atmospheric pressure is
P0.
Force F1 acting on the upper surface A is expressed
39. 39
Archimedes principle
The force F2 acting on the lower surface is:
volume of the body in the liquid is V, the resultant force F
from the pressure acting on the whole surface of the body
is:
47. 47
Archimedes principle Overall
Buoyancy force is equal to the
weight of displace fluid.
The volume of submerged
object in a fluid is equal to the
volume of displaced fluid.