EDUC6505 Engineering Studies 2 Assessment Task 3 Shannon Casey 3059509

1. ENGINEERING STUDIES
APPLICATIONS OF FLUID MECHANICS
EDUC6505 Engineering Studies 2
Assessment Task 3
Shannon Casey
3059509

2. CASE STUDY 1:
FLUID MECHANICS IN BRAKING SYSTEMS

3. Principles of Fluid
Mechanics

4. Pascal’s Principle
“Pascal’s Principle states that if the pressure at any point in a liquid
that is enclosed and at rest, is changed, then the pressure at all
points in the liquid is changes by the same amount” (OTEN, 2002c, p.
13).
“Pressure is described mathematically as a force exerted over an area
(or P = F ÷ A) and is measured I N/mm2 or Megapascals (MPa)”
(Metcalfe & Metcalfe, 2009, p. 172).

5. Pascal’s Principle
“According to Pascal’s Principle, a force applied to a confined fluid is
transmitted in all directions throughout the fluid regardless of the
shape of the container. Effectively this is shown in the system
depicted in the image below. If the input piston is forced
downwards, a pressure is created throughput the fluid, which acts
equally at right angles to the surface in all parts of the system”
(Metcalfe & Metcalfe, 2009, p. 172).

6. Pascal’s Principle
“If two cylinders connected (as shown in Figure 3.12) have a force
applied to the smaller cylinder, this would result in a given pressure.
By Pascal’s Principle, this pressure would be identical to the pressure
in the larger cylinder. Because the larger cylinder has more area, the
force emitted by the second cylinder would therefore be greater”
(Metcalfe & Metcalfe, 2009, p. 172).

7. Pascal’s Principle
This is represented by rearranging the pressure formula:
P=F÷A
to
F = PA
Because the pressure stayed the same in the second cylinder (but
area was increased) a larger resultant force was generated, including
a mechanical advantage” (Metcalfe & Metcalfe, 2009, p. 172).

8. Archimedes’ Principle
Archimedes’ Principle states that “when a body is wholly or partially
immersed in a fluid, it is acted upon by an upthrust which is equal to
the weight of the fluid displaced. This upthrust, or buoyancy, acts
through the centre of mass of the displaced fluid. The centre of mass
is therefore referred to as the centre of buoyancy” (OTEN, 2002c, p.
16).

9. Additional Reference Material
• Copeland, P. L. (2002). Engineering studies: the definitive guide.
(Vol. 1: the preliminary course). Helensburgh NSW: Anno Domini
2000 Pty Ltd.
• Metcalfe, P., & Metcalfe, R. (2009). Excel senior high school
engineering studies. Glebe NSW: Pascal Press.
• OTEN. (2002c). Part 4 : engineering mechanics, hydraulics and
communication - 2. Braking systems. Retrieved 12 May 2012, from
https://portalsrvs.det.nsw.edu.au/f5-w-
687474703a2f2f6c72722e646c722e6465742e6e73772e6564752e
6175$$/LRRDownloads/2938/1/41082ES_MOD%203%20BS%20Pa
rt%2004.doc

10. Examples of the uses
of hydraulic principles
in braking systems

11. Examples of the uses of hydraulic
principles in braking systems
“Pascal’s Principle is particularly important in automobile braking
systems. Most automobile braking systems are closed hydraulic systems
working on Pascal’s Principle” (Copeland, 2002, p. 90).
“If we consider the car breaking system as a closed hydraulic system
then we can apply Pascal’s Principle. The brake pedal is connected to the
master cylinder assembly under the bonnet. This consists of a piston in a
cylinder. By pressing the pedal, the piston is forced into the cylinder so
increasing the pressure in the master cylinder. This forcing the pads
against the discs and so applying the brakes” (Copeland, 2002, p. 90).

13. Disc Brakes
The disc brake is the most common type of
brake used in modern personal and public
transport vehicles such as cars and buses.
Disc brakes consist of “a rotating disc (rotor)
that is connected to the axle. Connected to
the suspension is a backing plate with a caliper attached. The caliper
wraps over the disc and houses two pads that are forced laterally against
the disc by a hydraulically operated piston. The frictional resistance
created retards the rotor. The disc brake offers better heat distribution
than the drum brake and also offers better wet-weather performance as
water is thrown off the disc by centrifugal force. Initially, the disc (rotor)
was solid but now they have vents through them (ventilated discs) or
they are drilled to further improve heat distribution”
(Copeland, 2002, pp. 78-79).

14. Disc Brakes
“One disadvantage of disc brakes
is that they have no natural
servo-assistance, so the force at
the pedal is very large. To reduce
the effort the pedal force is
“boosted”. A vacuum
booster, running off the engine
manifold, achieves this. This
magnifies the pedal effort the
driver provides
and improves stopping performance. Should a vacuum booster
fail, then the effort needed to stop a disc brake car is very large. Disc
breaks are also not good as hand brakes du to the lack of servo-
assistance” (Copeland, 2002, pp. 78-79).

15. Innovation in fluid
mechanics braking
systems

16. Anti-lock Braking Systems (ABS)
One of the biggest innovations in
braking systems was the successful
development of Anti-lock braking
systems (ABS). These braking
systems prevent the tendency of a
car to skid under braking. “When a
car skids in dry conditions it stops
quickly but not necessarily in a straight line. The unequal braking forces
at the wheels cause a turning moment about the car’s centre of
rotation, which tends to cause the car to turn “off-line” or swerve. In the
wet the wheels lock far more quickly and at a point way below maximum
braking force. With a front wheel lock-up the car loses the ability to steer
while the rear wheel lock-up often causes the tail to swing out. Both
situations can lead to a loss of control and consequently accidents”
(Copeland, 2002, p. 79).

17. Anti-lock Braking Systems (ABS)
“Car makers and brake designers have attempted to design braking
systems that will not lock up. This is usually achieved by using wheel
sensors and computer control over the braking circuit. When a wheel
begins to lock up and slow down, unlike other wheels, a wheel sensor
mounted on the wheel will sense this. It will send a message to the
computer to inform it of a wheel lock-up. The computer will then
release the pressure at the brake caliper to allow the wheel to spin
again. The brakes can then be reapplied and if the wheel locks again
the procedure is repeated” (Copeland, 2002, p. 79).

18. Anti-lock Braking Systems (ABS)
In Australia there is some concern
about the performance of ABS brakes
on gravel roads. Gravel roads need
the wheels to lock and dig through
the loose surface to the harder
surface beneath, but as an ABS brake
equipped car will not allow this to
happen, an ABS equipped car will not
stop as well on gravel. This is usually not a major concern for Japanese
or European car designers. Many cars with ABS also use the same
sensor to control wheel spin under acceleration” (Copeland, 2002, p.
79).

19. CASE STUDY 2:
FLUID MECHANICS IN LIFTING DEVICES

20. Development of
Lifting Devices

21. Elevators
Modern elevator or lift systems are driven by
hydraulic or electric motion. “Hydraulic lifts
are used extensively in low-rise buildings up
to five stories, for example small apartment
blocks, clubs, nursing homes and hospitals.
Speeds rarely exceed 0.75 m/s and no
overhead lifting gear is needed. They are
suitable for non-intensive duty designs”
(OTEN, 2002b, p. 15).
“Generally the total installation costs of hydraulic systems, including
building costs, are less than for electric traction alternatives although
performance efficiency is generally not equal” (OTEN, 2002b, p. 16).

22. Elevators
The use of hydraulics in elevator systems has allowed people and
materials to effortlessly more from floor to floor of a multi-story
building. This has been particularly useful for items which are
unsuitable to be take up staircases due to their size, shape and/or
weight.
“Without the availability of an efficient elevator system the focus of
our construction methods would possibly change from constructing
tall buildings in areas where land is scarce and expensive to a system
of low rise buildings constructed on less expensive land. This would
have the effect of increasing the urban sprawl as cities spread
outwards in search of suitable building sites” (OTEN, 2002a, p. 29).

23. Elevators
Direct acting hydraulic system Side acting hydraulic system

24. Cranes
“Cranes are one of the bigger lifting devices
you may see especially around large
construction sites. Scaled down cranes are
mounted on the back of tow trucks to lift
one end of a vehicle so it can be towed away
after an accident. However, most cranes are
used to lift things high off the ground, such
as for lifting materials to the upper floors of
a building under construction. All cranes are
designed to lift a suspended load from one
place to another” (OTEN, 2002a, p. 5).

25. Cranes
Telescopic extension cranes were a major
innovation in crane design from the 1960s.
Telescopic cranes have the advantage of
being able to work in confined spaces with
the boom extending only as far as needed.
An early example from 1966 is seen in the
picture on the right.
Telescopic cranes rely largely on the advantages of hydraulics for their
effectiveness. The hydraulic systems or theses cranes have “high
efficiency ratings because there are few moving parts and friction is
reduced by using oil-based fluids. Modern telescopic cranes can
reach to heights of about 60 metres or further if a trussed jib is
attached to the final boom extension” (OTEN, 2002a, p. 12).

26. Analysis of an
Innovation

27. Tower Cranes
An innovation in lifting devices is the self-
erecting tower crane. “Tower cranes have very
high towers or masts reaching unsupported
heights of 80 metres. Greater heights can be achieved if
the mast is tied to the frame of the building at regular
intervals” (OTEN, 2002a, p. 13).
Tower cranes have a climbing frame just below the cabin
that uses “large hydraulic rams to lift the cabin and jib one
mast section higher. The new mast section is lifted by the
crane itself into the position opened up by the climbing
frame. Once the new section is bolted to the lower
portion of the mast the whole operation can continue
upwards. When the crane is no longer required it simply
reverses the procedure to dismantle itself”
(OTEN, 2002a, p. 13).

28. Tower Cranes
Tower cranes do not have a high
capacity with 20 tonnes being about
the maximum lift rating. Their main
function is to move building materials
around the construction site especially
to the upper floors of tall buildings.
Some tower cranes have horizontal
jibs, which may reach 75 metres or more. This enables then to reach
from one side of a building site to the other even though the crane base
remains stationary. When working at the extreme end of the jib the
lifting capacity is reduced by at least half due to the greater turning
effect placed on the crane by the load” (OTEN, 2002a, pp. 13-14).
Tower cranes have allowed engineers to cope with the increased heights
of modern buildings and reduce their construction times. These cranes
also help to maintain safe working procedures by relieving workers from
carrying heavy loads.

29. Use of
hydraulics/pneumatics
as part of aeronautical
application

30. Wing Flap Hydraulics
Wing flaps and other components of
an aircraft are connected by complex
and sophisticated hydraulic networks.
“These networks contain high pressure
fluids capable of withstanding below-
freezing temperatures and are aided
by servos (small electrically operated
motors) and fluid pressure sensors.
The system provides pilots with power-assisted controls while the
sensors which are normally connected to onboard computer
systems, provide the pilot with immediate monitoring and feedback
on the position and status of these controls. Some of these controls
are designed with redundancy in mind. This means that if one
hydraulic network fails in a key area, a second network can continue
in its place.

31. Wing Flap Hydraulics
Aircraft hydraulic systems are simply a method of transmitting energy
or power from one place in the aircraft to another. The systems
involve an arrangement whereby liquid under pressure is used to
transmit this energy. Hydraulic systems take engine power and
convert it to hydraulic power by means of a hydraulic pump. This
power can be distributed throughout the airplane by means of tubing
that runs throughout the aircraft. Hydraulic power can be used in a
number of ways and in a variety of situations” (Metcalfe & Metcalfe,
2009, p. 235).

32. Wing Flap Hydraulics
The controlled movement of aircraft wing flaps is a good example of
the use of hydraulic power. In this instance “a hydraulic pump will
convert engine power before an actuating cylinder converts the
hydraulic power to mechanical power” (Metcalfe & Metcalfe, 2009, p.
235) thus allowing the movement of the flaps in the required
directions.
Wing flap hydraulics

33. Wing Flap Hydraulics
“An important part in the hydraulic system is the actuating cylinder. It’s
main function is to convert hydraulic or fluid power into movement or
mechanical power. Inside the actuating cylinder is a piston whose
motion is regulated by oil under pressure. The oil is in contact with both
sides of the piston head but at different and variable pressures.
Through the use of a selector
valve, high-pressure oil may be
directed into either side of the piston
head. Which side of the piston head
this pressure is directed to will
determine whether the shaft exerts a
pushing or a pulling force.
Piston flaps may be connected from the actuating cylinder to wing flaps
thus allowing the controlled movement of the flaps” (Metcalfe &
Metcalfe, 2009, pp. 235-236).

34. REFERENCES

35. Copeland, P. L. (2002). Engineering studies: the definitive guide. (Vol. 1: the
preliminary course). Helensburgh NSW: Anno Domini 2000 Pty Ltd.
Metcalfe, P., & Metcalfe, R. (2009). Excel senior high school engineering studies.
Glebe NSW: Pascal Press.
OTEN. (2002a). Part 1: lifting devices - developments. Lifting devices. Retrieved
13 May 2012, from https://portalsrvs.det.nsw.edu.au/f5-w-
687474703a2f2f6c72722e646c722e6465742e6e73772e6564752e6175$$
/LRRDownloads/3060/1/41094_ES_MOD_LD%2001.doc
OTEN. (2002b). Part 2: lifting devices - mechanics/hydraulics. Lifting devices.
Retrieved 13 May 2012, from https://portalsrvs.det.nsw.edu.au/f5-w-
687474703a2f2f6c72722e646c722e6465742e6e73772e6564752e6175$$
/LRRDownloads/3061/1/41094_ES_MOD_LD%2002.doc
OTEN. (2002c). Part 4 : engineering mechanics, hydraulics and communication -
2. Braking systems. Retrieved 12 May 2012, from
https://portalsrvs.det.nsw.edu.au/f5-w-
687474703a2f2f6c72722e646c722e6465742e6e73772e6564752e6175$$
/LRRDownloads/2938/1/41082ES_MOD%203%20BS%20Part%2004.doc