Fluid Mechanics- Fundamentals of mechanical engineering.pdf

This PDF provides an introduction to fluid mechanics, covering the fundamental principles of fluid behavior, flow, and pressure, and their applications in textile and engineering processes. It explains how fluids (liquids and gases) interact with machinery, fibers, and processes in the textile industry, helping to optimize production and ensure efficiency.

Key topics include:

Basic concepts of fluids: density, viscosity, and pressure

Types of fluid flow: laminar and turbulent

Fluid dynamics and fluid statics principles

Applications in textile processes such as spinning, dyeing, and finishing

Measurement and control of fluid flow in industrial systems

This document is intended for textile engineering students and professionals to gain a solid understanding of fluid behavior and its practical implications in textile operations.

1. Fundamentals of
Mechanical Engineering
IPE 203
Prepared By
Abdul Wadud
Assistant Professor (Mechanical)
Shahid AbdurRabSerniabatTextile Engineering College, Barishal.

2. ➢Fluid Mechanics & Machineries
➢Mechanics of Solids
➢Beams
➢Engineering mechanics
➢Mechanisms
➢Thermodynamics
➢Heat transfer
Topics

3. Fluid: -
Three states of matter: Solid, Liquid and Gas.
➢Liquid and gas are both fluids.
➢It flow under the action of the force.
➢It shape will change continuously as long as the
force is applied.
Fluid Mechanics is the study of fluids at rest (fluidstatics) and in motion (fluid dynamics).
Fluid Mechanics

4. Fluid Properties
1.Density
2.Specific weight
3.Specific gravity
4.Compressibility
5.Surface tension
6.Capillarity
7.Viscosity
1.Density (ρ)=
2. Specific weight (w) =
3. Specific gravity=
4. Compressibility : The variation in its volume, with the variation of pressure.

5. Surface tension:
to resist tensile stress.
➢The liquid surface has a tendency to reduce its surface as
small as possible.
➢That is why the falling drops of rain water become sphere.
➢Due to the cohesion between the
molecules of a liquid.
➢Mercury does not wet the glass.

6. Vertically force of surface tension= σ. πd cosα----------(1)
Weight of water = whA= wh×πd
2
/4 ----------(2)
h=
ασ
Effect of capillarity W= Specific weight
α= Angle of contract
σ= Force of surface tension
(1) = (2)
The phenomenon of rising water in the tube of small diameter.
Capillarity

7. Viscosity
Controls its rate of flow
Effect of temperature on the viscosity:-
Thick liquids like oil, ghee when heated become less viscous. Viscosity is a function of
temperature.

8. Newton‘s Law of viscosity:-
The shear stress on a layer of a fluid is directly proportional to the rate of shear strain ( velocity
gradient).
Newtonian fluid: A fluid, which obeys Newton‘s law of viscosity.
Non-Newtonian fluid: A fluid, which does not obey Newton‘s law of viscosity.
μ= Constant of proportionality.

9. = wh
The intensity of pressure at any point, in a liquid, is proportional to its depth.
Pressure, p =
=
Fluid Pressure
➢A liquid is contained in a vessel, it exerts force at all point on the sides and bottom of the
container. Force per unit area is called pressure.
There will be some pressure on the cylinder base due to weight of the liquid in it.
W= Specific weight
h= height of liquid
A= Area of the cylinder base
➢Intensity of pressure: pressure at a point. Pressure right angles to the surface, p= P/A

10. Manometer: pressure measuring device, we can measure comparatively high and negative
pressure.
Types of manometers-
1.Simple manometer: One end is attached to the gauge point and other is open to the
atmosphere.
2.Differential manometer: Measuring the difference of pressure, between two points in
a pipe or in two different pipes.
Simple manometer
Differential manometer
Manometer

11. 3. Micro manometer: Cross-sectional area
of one of the side is made much larger.
4.Inverteddifferentialmanometer:
Measuringdifferenceoflowpressureand
twoendsareconnectedtothepoint.

12. h
1= Height of the light liquid
h
2= Height of the heavy liquid
h= Pressure in the pipe
S
1= Specific gravity of the light liquid
S
2= Specific gravity of the heavy liquid
Pressure in the left and right above the datum line (A-A) are equal
h + s
1h
1= s
2h
2
Working principle of a simple manometer

13. h
A+ S
1h
1=hS
3+ h
2S
2+ h
B
Working principle of a differential manometer
{A and B at different levels and
containing different liquids}
S
2
S
1
S
3
Pressure in the left and right above the datum line (X-X’) are equal

14. h
A+ S
1H + 100S
1= h
B+ S
1H + 100 S
2
h
A–h
B= 100S
2–100 S
1= 100( 13.6 -0.8) = 1.28 m
Difference of pressure, p= w (h
A–h
B)
= 9.81 ×1.28 = 12.56 KPa
S
1= 0.8
S
2= 13.6

15. Hydrostatics:
Hydrostatics means the study of pressure, exerted by a liquid at rest.
(We dive deeper and deeper, we fell more and more uneasiness)
Total pressure on an immersed surface: 1. Horizontal 2. vertical 3. inclined

19. Fluid flow measurement
Venturimeter: Finding out the discharge of a liquid flowing in a pipe.
Orifice meter: To measure the discharge of a liquid in a pipe.
Pitottube: To determine the velocity of flow.
Venturimeter Orifice meter
Pitottube

20. Types of flows in a pipe
1.Uniform flow: velocity of liquid particles at all
section of a pipe are equal.
2.Non-Uniform flow:
3. Laminar flow : liquid particles has a definite path
and do not cross each other.
4.Turbulent flow : liquid particles cross each other.
5. Steady flow: Quantity of liquid flowing per second is
constant.
6. Unsteady flow:

21. Equation of continuity
The quantity of liquid passing per second is the same at all section
.
a= Cross-sectional area of the pipe
V =Velocity of the liquid
Total quantity of liquid passing through section 1-1,
Total quantity of liquid passing through section 2-2,
Total quantity of liquid passing through section 3-3,
All section Q is the same,

22. Bernoulli's Equation
For a perfect incompressible liquid, flowing in a continuous stream, the total energy of a
particle remains the same, while the particle moves from one point to another.
Z +
Z= Potential energy,
Proves Bernoull’sEquation,

23. ➢The velocity of every liquid particle, across any cross-section of a pipe, is uniform.
But in actual practice, it is not so.
➢No external force is acting on the liquid.
But, in actual practice, it is not so.
➢There is no loss of energy of the liquid particle while flowing.
But, in actual practice, it is rarely so.
Limitations of Bernoull’sEquation.

24. Thediameterofapipechangesfrom200mmatasection5metresabovedatumto50mmata
section3metersabovedatum.Thepressureofwateratfirstsectionis500kPa.Ifthevelocity
offlowatthefirstsectionis1m/s,determinetheintensityofpressureatthesecondsection.
d
1= 200mm= 0.2 m
Z
1= 5 m
d
2=50 mm= 0.05 m
Z
2= 3m
P
1= 500 KPa= 500KN/m
2
V
1= 1 m/s
.
= 16 m/s

25. Loss of head in a pipe
➢When a liquid is flowing in a pipe, it loses its energy( or termed as head) due to friction.
1. Loss of head due to
sudden enlargement
2. Loss of head due to
sudden contraction
3. Loss of head due to an
obstruction in a pipe
4. Loss of head at the entrance in a pipe5. Loss of head due to the exit in a pipe

26. Consider a uniform long pipe, l= Length, d= Dia.
v = Velocity of water in the pipe
p
1=Intensity of pressure at section (1-1)
p
2= Intensity of pressure at section (2-2)
Darcy’s Formula for loss of head

27. Froude experiment, Frictional resistance
F.R
F.R
Put,

28. Water is flowing through a pipe 1500m long with a velocity of 0.8 m/s. What should be
the diameter of the pipe, if the loss of head due to friction is 8.7m. Take coefficient of
friction as 0.005.
d= 0.225 m

29. Air Compressor

30. ➢An air compressor is a machine to compress the air and to raise its pressure.
➢The air compressor sucks air from the atmosphere, compresses it and then
delivers the same under a high pressure.
Classification of air compressors
According to working
1. Reciprocating compressor 2. Rotary compressor
According to action
1. Single acting 2. Double acting

31. Reciprocatingcompressor:Thepressureoftheairisincreasedinitscylinderwiththehelpof
amovingpiston.
Working of single stage Reciprocating air compressor:

32. Rotaryaircompressor:Airisentrappedbetweentwosetsofengagingsurface
andthepressureofairisincrease.

33. Reciprocating air compressorRotary air compressor
Maximum delivery pressure is 1000 barMaximum delivery pressure is 10 bar
Maximum air discharge is 300 m
3
/min Maximum air discharge is 3000 m
3
/min
They are suitable for low discharge ofair
at high pressure
They are suitable for large discharge of
air at low pressure
Speed of air compressor is low Speed ofair compressor is high

35. Practical : Study of a flow meter
Size : 4 inch (100 mm)
Accuracy: 0.2%
Maximum water pressure:10 bar
Water temperature: 30
0
C
Maximum Reading: 999999 m
3
Flow range: 18-60 m
3
/h
➢High quality flow meter in the water measurement.
➢Including measuring of boiler fuel, diesel fuel, kerosene etc
➢Feature: High accuracy, Compact design, Excellent durability