The document presents an overview of the study of fluids. It discusses the different classes of fluids including liquids and gases. It describes various fluid properties such as density, viscosity, and compressibility. The document outlines different types of fluid flow, such as laminar and turbulent flow. It also discusses applications of fluid mechanics in various engineering fields such as biomedical, chemical, and civil engineering.

1. Study of Fluids
Presented By:
Sadhana Singh

2. Outlines
• Introduction
• Classes of Fluids
• Properties of Fluids
• Types of Fluids Flow
• Fluids in Motion
• Applications of Fluids
• Conclusions
• References
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3. Introduction
• A fluid is anything that flows, usually a liquid or a gas
• Fluids are treated as continuous media, and their
motion and state can be specified in terms of the
velocity u, pressure p, density ρ , etc evaluated at
every point in space x and time t
• A fluid cannot resist a shear stress by a static deflecti
on and it moves and deforms continuously as long
as the shear stress is applied
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4. Cont’d…
• Fluid mechanics is the study of fluids either in motion
(fluid dynamics) or at rest (fluid statics)
• Both liquids and gases are classified as fluids
• If the fluids are at rest, the study of them is called
fluid statics
• If the fluids are in motion, the study of them is called
fluid dynamics
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5. Cont’d…
• The science and technology of the mechanical
properties of liquids is called hydraulics
• Similarly, the science and technology of the
mechanical properties of air and other gases is called
pneumatics
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6. Cont’d…
• The Fluid density is defined as:
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7. Cont’d…
• The science and technology of the mechanical
properties of liquids is called Hydraulics.
• Similarly, the science and technology of the
mechanical properties of air and other gases is called
pneumatic.
Figure 1: Fluid
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8. Cont’d…
Figure 2: Effects of Viscosity and shape on the fluid flow
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9. Classes of Fluids
• Two classes of Fluids are:
 Liquids
Are composed of relatively close‐packed molecules
with strong cohesive forces
Liquids have constant volume
Will form a free surface in a gravitational field if
unconfined from above
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10. Cont’d…
• In a liquid, the particles move fast enough that they
can’t stay in a rigid structure but they still want to
stay close by.
Figure 3: Liquid crystals
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11. Cont’d…
Gases
Molecules are widely spaced with negligible cohesive
forces
A gas is free to expand until it encounters confining
walls
A gas has no definite volume, and it forms an atmosp
here when it is not confined
Gravitational effects are rarely concerned
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12. Cont’d…
• In a gas, however, the particles are moving even
faster and fly by each other, bouncing off the edges
of the container.
Evaporation: a liquid
molecule becoming a gas
molecule
Figure 4: Gas molecule
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13. Solids
• In a solid, the particles are moving slowly enough
that this attraction keeps them in a rigid structure.
• Has definite volume
• Has definite shape
• Molecules are held in specific locations
by electrical forces
• vibrate about equilibrium positions
• Can be modeled as springs connecting molecules
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14. Cont’d…
Figure 5: Both are solids
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15. Properties of Fluids
• Density or Mass Density:
Density or mass density of a fluid is defined as ratio
of the mass of a fluids to its volume. Thus mass per
unit volume of a fluid is called density.
Thus unit of density in S.I. is kg/m3
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16. Cont’d…
• Specific weight or weight density:
Specific weight or weight density of a fluid is defined
as ratio between the weights of fluids and to its
volume. Thus weight per unit volume of a fluid is
called weight density.
Thus unit of specific weight in S.I. is N/m3
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17. Cont’d…
• Specific Volume:
Specific volume of a fluid is defined as volume of a
fluid occupied by a unit mass or volume per unit mass
of a fluid.
Thus specific volume is the reciprocal of mass
density. It is expressed as m3/kg. It is commonly
applied to gases.
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18. Cont’d…
• Specific gravity:
Specific gravity is defined as the ratio of weight
density of a fluid to the weight density of a standard
fluid.
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19. Types of Fluids Flow
• Fluid evenness: Steady or unsteady flow
• Fluid squeezability: Compressible or incompressible
flow
• Fluid thickness: Viscous or nonviscous flow
• Fluid spinning: Rotational or irrotational flow
• Division of flows with respect to distance
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20. Fluid evenness: Steady or unsteady flow
• Fluid flow can be steady or unsteady, depending on
the fluid’s velocity:
• Steady. In steady fluid flow, the velocity of the fluid
is constant at any point.
• Unsteady. When the flow is unsteady, the fluid’s
velocity can differ between any two points.
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21. Fluid squeezability: Compressible or
incompressible flow
• Fluid flow can
be compressible or incompressible, depending on
whether you can easily compress the fluid.
• Liquids are usually nearly impossible to compress,
whereas gases (also considered. a fluid) are very
compressible.
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22. Fluid thickness: Viscous or nonviscous
flow
• Liquid flow can be viscous or nonviscous. Viscosity is
a measure of the thickness of a fluid, and very gloppy
fluids such as motor oil or shampoo are called viscous
fluids.
• Viscosity is actually a measure of friction in the fluid.
When a fluid flows, the layers of fluid rub against one
another, and in very viscous fluids, the friction is so
great that the layers of flow pull against one other and
hamper that flow.
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23. Fluid spinning: Rotational or irrotational
flow
• Fluid flow can be rotational or irrotational. If, as you
travel in a closed loop, you add up all the components
of the fluid velocity vectors along your path and the
end result is not zero, then the flow is rotational.
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24. Division of flows with respect to distance
• Uniform flow – constant section area along flow path
• Non-uniform flow – variable section area
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25. Laminar Flow
Flow along parallel paths
 Shear stress proportional to velocity gradient
(τ = μ⋅du/dy)
• Disturbances in the flow are rapidly damped by
viscous action
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26. Turbulent Flow
Fluid particles moves in a random manner and not in
layers
 Length scales >> molecular scales in laminar flow
 Rapid continuous mixing
 Inertia forces and viscous forces of importance
Figure 6: Turbulent Flow
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27. Fluids in Motion
• All fluids are assumed in this treatment to exhibit
streamline flow.
• Streamline flow is the motion of a fluid in which
every particle in the fluid follows the same path past a
particular point as that followed by previous particles.
Figure 7: Streamline flow
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28. Fluid System And Control Volume
• Fluid system: Specified mass of fluid within a closed
surface
• Control volume: Fix region in space that can’t be
moved or change shape. Its surface is called control
surface.
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29. Applications
• Fluids is extremely important in many areas of
engineering and science. Examples are:
Biomechanics
Blood flow through arteries
Meteorology and Ocean Engineering
Movements of air currents and water currents
Chemical Engineering
Design of chemical processing equipment
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30. Cont’d…
Mechanical Engineering
Design of pumps, turbines, air-conditioning
equipment, pollution-control equipment, etc.
Civil Engineering
Transport of river sediments
Pollution of air and water
Design of piping systems
Flood control systems
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31. Conclusions
• A fluid is a substance that continually deforms(flows)
under an applied shear stress.
• Fluids are a subset of the phases of matter and
include liquids, gases, plasmas and, to some
extent, plastic solids.
• Fluids can be defined as substances which have
zero shear modulus or in simpler terms a fluid is
a substance which cannot resist any shear
force applied to it.
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32. References
• http://www.dummies.com/how-to/content/the-different-types-of-
fluid-flow.html
• Genick Bar Meir, “ Basics of fluid mechanics”, July 25, 2013.
• M. Bahrami, “Introduction and properties of fluids”, Spring
2009.
• T. J. Pedley, “Introduction to Fluid dynamics”, LECTURES
ON PLANKTON AND TURBULENCE. C. MARRASÉ, E.
SAIZ and J.M. REDONDO (eds.), 1997.
• Bird, Byron; Stewart, Warren & Lightfoot, Edward
(2007). Transport Phenomena. New York: Wiley, Second
Edition. p. 912. ISBN 0-471-41077-2.
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