CE - 203
Fluid Mechanics
Dr. Anand Kr. Sinha
Professor (Civil and Environmental Engineering)
Birla Institute of Technology, Mesra
Monsoon Semester, 2022-2023
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Civil Engineering
Programme Educational Objectives (PEO)
1. Attain the analytical expertise to create,
analyse, formulate, and solve challenging
problems in the field of Civil Engineering;
and recognize and develop the necessary
and suitable tools for the same.
2. Develop technical and management flair to
take responsibility for engineering projects
and research programs significantly.
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Civil Engineering
Programme Educational Objectives (PEO)
3. Uncover multidisciplinary approach and corelate engineering issues to social and
human background in broader sense, in
which their engineering helping hand will be
utilised.
4. Develop attitude of lifelong learning for
becoming successful civil engineers.
5. Implant sensitivity towards ethics, public
policies and their responsibilities towards
the society.
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Civil Engineering
Programme Outcomes (PO)
1. Engineering knowledge: Apply the
knowledge of mathematics, science,
engineering fundamentals, and an
engineering specialization to the solution of
complex engineering problems.
2. Problem analysis: Identify, formulate, review
research literature, and analyze complex
engineering problems reaching
substantiated conclusions using first
principles of mathematics, natural sciences,
and engineering sciences.
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Civil Engineering
Programme Outcomes (PO)
3. Design/development of solutions: Design solutions
for complex engineering problems and design
system components or processes that meet the
specified needs with appropriate consideration for
the public health and safety, and the cultural,
societal, and environmental considerations.
4. Conduct investigations of complex problems: Use
research-based knowledge and research methods
including design of experiments, analysis and
interpretation of data, and synthesis of the
information to provide valid conclusions.
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Civil Engineering
Programme Outcomes (PO)
5. Modern tool usage: Create, select, and apply
appropriate techniques, resources, and modern
engineering and IT tools including prediction
and modeling to complex engineering activities
with an understanding of the limitations.
6. The engineer and society: Apply reasoning
informed by the contextual knowledge to
assess societal, health, safety, legal and cultural
issues and the consequent responsibilities
relevant to the professional engineering
practice.
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Civil Engineering
Programme Outcomes (PO)
7. Environment and sustainability: Understand
the impact of the professional engineering
solutions in societal and environmental
contexts, and demonstrate the knowledge of,
and need for sustainable development.
8. Ethics: Apply ethical principles and commit to
professional ethics and responsibilities and
norms of the engineering practice.
9. Individual and team work: Function effectively
as an individual, and as a member or leader in
diverse teams, and in multidisciplinary
settings.
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Civil Engineering
Programme Outcomes (PO)
10.Communication: Communicate effectively on
complex engineering activities with the engineering
community and with society at large, such as, being
able to comprehend and write effective reports and
design documentation, make effective presentations,
and give and receive clear instructions.
11.Project management and finance: Demonstrate
knowledge and understanding of the engineering and
management principles and apply these to one’s own
work, as a member and leader in a team, to manage
projects and in multidisciplinary environments.
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Civil Engineering
Programme Outcomes (PO)
12.Life-long learning: Recognize the need for,
and have the preparation and ability to engage
in independent and life-long learning in the
broadest context of technological change.
Program Specific Outcomes (PSO)
1. Plan, analyse, and design infrastructural
projects and its components in various areas
of Civil Engineering like Structural Engineering,
Geotechnical Engineering, Water Resources
Engineering, Environmental Engineering, and
Transportation Engineering.
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Civil Engineering
Program Specific Outcomes (PSO)
2. Execute the construction of buildings and
other components of various projects in
Civil Engineering including its layout,
management, and quality control.
3. Implement the provisions made in Indian
Standard Codes/ other relevant codes/
specifications/ guidelines and applicable
laws including labour laws and
environmental laws.
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Civil Engineering
Specialisations
• Structural Engineering
• Geotechnical Engineering
• Water Resources Engineering
• Environmental Engineering
• Transportation Engineering
• Other Specialisations like Surveying,
Construction Technology etc
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Water Resources Engineering
• Fluid Mechanics
• Water Resources Engineering
Electives
• Fluid Dynamics
• Open Channel Flow
• Design of Hydraulic Structures
• Ground Water Engineering
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Fluid Mechanics
Course Objectives
• To get introduced about the concepts of fluid
mechanics useful for civil engineering applications.
• To apply the concepts of fluid mechanics to analyse
and solve engineering problems involving fluids such
as flow in pipes, open channels, jets, turbines and
pumps, hydraulic structures, rivers and in subsurface both at static and dynamic conditions.
• To understand and analyse various types of flows in
open channels.
• To design pumps and hydraulic turbines.
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Fluid Mechanics
Course Outcomes
1. Examine and interpret the behaviour of fluids
using its properties. (K1, K2)
2. Solve the engineering problems using principles
of fluid statics and kinematics. (K3, K4, K5)
3. Understand and analyse the dynamic behaviour
of fluids using concepts of fluid dynamics. (K2,
K3, K4)
4. Apply the principles of fluid mechanics to
investigate open channel flows. (K2, K3, K4, K5)
5. Analyse and design hydraulic pumps and
turbines. (K3, K4, K5)
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Bloom’s Taxonomy
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Fluid Mechanics
Course Modules
• Fluid Properties
• Fluid Statics and Kinematics
• Fluid Dynamics
• Open Channel Flow
• Hydraulic Pumps and Turbines
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Fluid Properties
• The solids, liquids, and gases exhibit different
characteristics on account of their different
molecular structure.
• All substances consist of vast number of
molecules separated by empty space.
• The molecules are continuously moving within
the substance.
• In solids, the molecules are closely spaced and
the attraction between molecules is large on
account of which there is very little movement
of molecules within the solid mass.
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Fluid Properties
• In liquids, the spacing between the molecules is
relatively large and the force of attraction
between the molecules is relatively less due to
which the molecules can move freely within the
liquid mass but the force of attraction is
sufficient to keep the liquid together in a
definite volume.
• In gases, the space between the molecules is
still larger and the force of attraction is much
less due to which the molecules of gases have
greater freedom of movement so that the
gases fill completely the container in which
they are placed.
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Fluid Properties
• In spite of larger mobility and spacing of the
molecules, for mechanical analysis a fluid is
considered to be continuum (a continuous
distribution of matter with no voids or empty
spaces).
• A solid can resist tensile, compressive, and
shear forces.
• A fluid can resist only compressive force. When
subjected to a shear force, a fluid deforms
continuously as long as the force is applied.
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Fluid Properties
• As the fluid flows, there exist shear stresses
between the adjacent layers.
• Gases can be compressed much readily as
compared to liquids, which may be
regarded as incompressible.
• The liquids may have a free surface.
Fluid
• A fluid may be defined as a substance
which is capable of flowing.
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Fluid Properties
• It has no definite shape of its own but
conforms to the shape of the containing vessel.
• Even a small amount of shear force exerted on
a fluid will cause it to undergo a deformation
which continues as long as the force continues
to be applied.
Liquid
• A liquid is a fluid which possess a definite
volume which varies only slightly with
temperature and pressure.
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Fluid Properties
Gas
• A gas is a fluid which is compressible and
possess no definite volume but it always
expands until its volume is equal to that of
container.
Vapour
• A vapour is a gas whose temperature and
pressure are such that it is very near the
liquid state.
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Fluid Properties
Ideal Fluids
• Ideal fluids are those which have no viscosity
and surface tension and are incompressible.
Real Fluids
• Real fluids are those fluids which are actually
available in nature.
Fluid Mechanics
• Fluid Mechanics is that branch of Science
which deals with the behaviour of fluids at
rest as well as in motion.
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Fluid Properties
Two Distinct School of Thought
i. Classical Hydrodynamics – deals with
theoretical aspects of fluid flow, ideal fluid
concept
ii. Hydraulics – deals with practical aspects of
fluid flow developed from experimental
findings, more of empirical nature
• The empirical formulae developed in
hydraulics can not be extended to fluids other
than water and in the field of Aerodynamics.
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Fluid Properties
• So a new approach of Fluid Mechanics
was developed taking a balanced view of
the theorists and experimentalists.
Properties of Fluids
Mass Density
• Mass density of a fluid is the mass which
it posses per unit volume.
• It is also called specific mass.
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Fluid Properties
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Fluid Properties
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Fluid Properties
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Fluid Properties
Specific Gravity or Relative Density
• Specific gravity is the ratio of specific
weight of a fluid to the specific weight of a
standard fluid.
• For liquids, the standard fluid is water at
4⁰C. Whereas for gases, standard fluid may
be either hydrogen or air at some specified
temperature and pressure.
• Value for water = 1
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Fluid Properties
Viscosity
• Viscosity is that property of a fluid by virtue
of which it offers resistance to the
movement of one layer over an adjacent
layer.
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Fluid Properties
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Fluid Properties
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Fluid Properties
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Fluid Properties
• Viscosity is practically independent of
pressure but varies widely with temperature.
• For gases, viscosity increases with increase
in temperature but for liquids, it decreases
with increase in temperature.
• Because in liquids, the viscosity is governed
by the cohesive forces between the
molecules, whereas in gases, molecular
activity plays a dominant role.
Rheological Diagram
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Rheological Diagram
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Fluid Properties
• The fluids with which the engineers have to
deal are Newtonian and Fluid Mechanics
generally refers to Newtonian fluids.
• The study of Non-Newtonian fluids is termed
as Rheology.
Problem – 1
A cylinder of 0.3 m diameter rotates
concentrically inside a fixed cylinder 0.31 m
diameter. Both the cylinders are 0.3 m long.
Determine the viscosity of the liquid which fills
the space between the cylinders if a torque of
0.98 N-m is required to maintain an angular
velocity of 60 rpm.
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Fluid Properties
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Fluid Properties
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Fluid Properties
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Fluid Properties
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Fluid Properties
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Fluid Properties
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Fluid Properties
Vapour Pressure
• Vapourisation of liquids occurs because of
continuous escaping of molecules through
the free liquid surface.
• When the liquid is confined in a closed
vessel, the ejected vapour molecules get
accumulated in the space between the free
liquid surface and the top of the vessel.
• This accumulated vapour exerts a partial
pressure on the liquid surface which is
known as vapour pressure of the liquid.
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Fluid Properties
• Vapour pressure increases with temperature.
• If the external absolute pressure imposed on
the liquid is reduced to such an extent that it
is equal to or less than vapour pressure, the
boiling starts, whatever be the temperature.
• In any flow system, if the pressure at any
point in the liquid approaches the vapour
pressure, vapourisation starts, resulting in
pockets of dissolved gases and vapours,
which are carried by the flow in to a region of
high pressure, where they collapse.
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Fluid Properties
• Their collapse gives rise to high impact pressure,
due to which the adjoining boundaries may get
eroded and cavities are formed on them.
• This phenomenon is known as cavitation.
• Mercury has a very low vapour and hence it an
excellent fluid to be used in barometer.
Bulk Modulus of Elasticity
• All fluids may be compressed by application of
external force, and when the external force is
removed the compressed volume expands to the
original volume.
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Fluid Properties
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Fluid Properties
• Air is 20,000 times more compressible than
water.
• Values for Steel – 2.1 X 1011 N/m2, 2.1 X 106
kgf/cm2
• Water is 100 times more compressible than
steel.
• Compressibility increases with increase in
pressure.
• For water, K is nearly doubled when the
pressure is increased from 1 atm to 3500
atm.
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Fluid Properties
• In case of liquids, there is decrease in K with
increase in temperature. But for gases, K
increases with increase in temperature because
the pressure increases with temperature.
• K for water is very high. Therefore, the
compressibility of water may be neglected in
most of the cases.
• However, in case of sudden closure of valve or
water hammer the change in pressure is large
and sudden and the liquid is considered as
compressible.
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Fluid Properties
• On the other hand, gases are easily
compressible, hence the effects of
compressibility can not be neglected.
Surface Tension
• Cohesion is the intermolecular attraction
between the molecules of the same liquid.
• Adhesion is the attraction between the
molecules of a solid boundary surface in
contact with the liquid.
• Cohesion enables a liquid to resist tensile
stress while adhesion enables it to stick to
another body.
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Fluid Properties
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Fluid Properties
• Unit – N/m, kgf/m, kgf/cm
• Dimension – FL or MT
• Surface tension for all liquids decreases as
temperature rises.
• It is also dependent on the fluid in contact with
liquid surface.
• The surface tension is usually quoted in
contact with air.
• Values for water – 0.075 N/m or 0.0075 kgf/m
at 19⁰C and 0.06 N/m or 0.006 kgf/m at 100⁰C
-1
-2
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Fluid Properties
• When a droplet is separated from the main body
of liquid, then due to surface tension there is a
net inward force exerted over the entire surface
of the droplet, which causes the surface of the
droplet to contract from all sides resulting in
increase in internal pressure within the droplet.
• This contraction continues till the inward force
due to surface tension is balanced with the
internal pressure and the droplets forms in to
spheres, which is the shape for minimum
surface area.
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Fluid Properties
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Fluid Properties
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Fluid Properties
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Fluid Properties
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