fluid mechanics

1. FLUID MECHANICS
FLUID MECHANICS
Fluid Mechanics is that branch
Fluid Mechanics is that branch
of science which deals with
of science which deals with
behaviour of the fluids at rest
behaviour of the fluids at rest
as well as in motion
as well as in motion

2. Fluid mechanics can we divided
Fluid mechanics can we divided
into 3 divisions:
into 3 divisions:
Hydrostatics: that studies the mechanics of
Hydrostatics: that studies the mechanics of
fluids at absolute and relative rest.
fluids at absolute and relative rest.
Kinematics: deals with translation, rotation and
Kinematics: deals with translation, rotation and
deformation of fluid without considering the
deformation of fluid without considering the
force and energy causing such a motion.
force and energy causing such a motion.
Dynamics: that prescribes the relation between
Dynamics: that prescribes the relation between
velocities and acceleration and the forces which
velocities and acceleration and the forces which
are exerted by or upon the moving fluids.
are exerted by or upon the moving fluids.

3. What is Fluid ?
What is Fluid ?
Matter exist in two principal forms:
Matter exist in two principal forms:
• Solid
Solid
• Fluids
Fluids
Fluids are further sub-divided into:
Fluids are further sub-divided into:
• Liquid
Liquid
• Gas
Gas

4. For all practical purposes , the
For all practical purposes , the
liquids and solids can be regarded as
liquids and solids can be regarded as
incompressible.This means that
incompressible.This means that
pressure and temperature have
pressure and temperature have
practically no effect on them.Eg
practically no effect on them.Eg
Water, Kerosene,petrol etc.
Water, Kerosene,petrol etc.
But Gases are readily compressible
But Gases are readily compressible
fluids.They expand infinitely in the
fluids.They expand infinitely in the
absence of pressure and contract easily
absence of pressure and contract easily
under pressure. Eg air ,ammonia etc.
under pressure. Eg air ,ammonia etc.

5. A DAY FULL OF FLUID
A DAY FULL OF FLUID
MECHANICS
MECHANICS

6. YOU WOKE UP IN THE MORNING AND THE
YOU WOKE UP IN THE MORNING AND THE
ROOM IS COOL.
ROOM IS COOL.
Coolant circulating
Coolant circulating
Inside it and cool
Inside it and cool
Air which it gives
Air which it gives
is Fluid
is Fluid

7. After that you washed your face at
After that you washed your face at
the sink. The water which comes at
the sink. The water which comes at
your tap is fluid and has come
your tap is fluid and has come
through the piping system which
through the piping system which
also comes under fluid mechanics.
also comes under fluid mechanics.

8. After that you decided to have your
After that you decided to have your
breakfast.
breakfast. The coolant moving
inside the small pipes at the back of
your
refrigerator, and the air circulating
inside it are both fluids.

10. After finishing your breakfast,
After finishing your breakfast, You decided to
do some cleaning before
heading to the school. Proper suction of air
and filtering the dust requires the knowledge
of Fluid Mechanics.

11. After that you turned on your T.V
After that you turned on your T.V
to get the morning news.
to get the morning news.
Nothing good, war again
Nothing good, war again

12. UNMANNED AIR VEHICLE USED BY
UNMANNED AIR VEHICLE USED BY
US ARMY IN AFGHANISTAN
US ARMY IN AFGHANISTAN

13. MISSILE AERODYNAMICS
MISSILE AERODYNAMICS

14. Now it’s the time to go to college,
Now it’s the time to go to college,
otherwise you will get late
otherwise you will get late
A mixture of
A mixture of fuel
fuel like petrol and
like petrol and air
air is forced
is forced
by atmospheric (or greater) pressure into
by atmospheric (or greater) pressure into
the cylinder through the intake port
the cylinder through the intake port

15. Before your class you went to PC
Before your class you went to PC
lab and took a print out of your
lab and took a print out of your
assignment. Inkjet printing also
assignment. Inkjet printing also
involves fluid mechanics.
involves fluid mechanics.

16. Knowledge of Fluid Mechanics is
Knowledge of Fluid Mechanics is
essential for proper design of
essential for proper design of
Ships.
Ships.

17. Otherwise without the proper
Otherwise without the proper
knowledge of fluid mechanics,
knowledge of fluid mechanics,
What will happen
What will happen

18. In this subject, topic on Model
In this subject, topic on Model
Studies is there which is very
Studies is there which is very
important for civil engineers.
important for civil engineers.
Model Tests on civil engineering structures
Model Tests on civil engineering structures
such as Dams, canals to predict the
such as Dams, canals to predict the
working of full size structure and river
working of full size structure and river
models assist a civil engineer in the
models assist a civil engineer in the
design of flood control structure as well as
design of flood control structure as well as
in the analysis of sediment movement in
in the analysis of sediment movement in
rivers.
rivers.

19. Significance of Fluid Mechanics
Significance of Fluid Mechanics
• Design of wide range of hydraulic structures
Design of wide range of hydraulic structures
(dams,canals) and machinery
(dams,canals) and machinery
( pumps,turbines).
( pumps,turbines).
• Fluidic control devices; both pneumatic and
Fluidic control devices; both pneumatic and
hydraulic.
hydraulic.
• Design and analysis of gas turbine , rocket
Design and analysis of gas turbine , rocket
engine, super sonic aircrafts.
engine, super sonic aircrafts.
• Human circulatory system i.e the flow of blood in
Human circulatory system i.e the flow of blood in
veins and the pumping action of heart.
veins and the pumping action of heart.

20. Ideal Fluid: A fluid is said to be
Ideal Fluid: A fluid is said to be
ideal if it is assumed to be both
ideal if it is assumed to be both
incompressible and inviscid (non-
incompressible and inviscid (non-
viscous).
viscous).
Ideal fluid has no surface tension and viscosity is
Ideal fluid has no surface tension and viscosity is
zero and no frictional forces are set up even
zero and no frictional forces are set up even
during the fluid motion.
during the fluid motion.
Ideal Fluids are imaginary and do not exist in
Ideal Fluids are imaginary and do not exist in
nature .
nature .

21. Real Fluid: Practical Fluid have
Real Fluid: Practical Fluid have
surface tension, viscosity and
surface tension, viscosity and
compressibility.
compressibility.
Whenever motion takes place, the
Whenever motion takes place, the
tangential or shear forces always come
tangential or shear forces always come
into play due to viscosity and some
into play due to viscosity and some
frictional work is done.
frictional work is done.

22. Density (ρ)
Density is the mass of the fluid per unit
volume
ρ = m/v
Units : Kg/m3

23. Specific Gravity(s):
Specific Gravity(s):
The specific gravity is the ratio of the
density or specific weight of the fluid to
the density or specific weight of water, at
a temperature of 4o
C
For Gases the standard fluid is taken either
air at 00
C or Hydrogen at the same
temperature.

24. It is dimensionless quantity.
A Statement that the specific gravity of
A Statement that the specific gravity of
mercury is 13.6 implies that its weight (or
mercury is 13.6 implies that its weight (or
mass) in 13.6 times that of the same
mass) in 13.6 times that of the same
volume of water.
volume of water.
In simple words, mercury is 13.6 times
In simple words, mercury is 13.6 times
heavier than water.
heavier than water.

25. Specific Volume: Represents the
Specific Volume: Represents the
volume per unit mass of fluid.
volume per unit mass of fluid.
Specific Volume is the inverse of the mass
Specific Volume is the inverse of the mass
density.
density.
v= V/m
v= V/m
or v=1/
or v=1/ρ
The concept of specific volume is found to
The concept of specific volume is found to
be more useful in the study of flow of
be more useful in the study of flow of
compressible fluids i.e gases.
compressible fluids i.e gases.

26. Viscosity: It is the property of the
Viscosity: It is the property of the
fluid by virue of which it offers
fluid by virue of which it offers
resistance to shear or angular
resistance to shear or angular
deformation.
deformation.
Mollases,tar, glycerine are highly viscous
Mollases,tar, glycerine are highly viscous
fluids.
fluids.
Water,air,petrol have very small viscosity
Water,air,petrol have very small viscosity
and are called thin fluids.
and are called thin fluids.

27. Newton’s Law of Viscosity
Newton’s Law of Viscosity
τ= µ (du/dy)
(du/dy)
Where, du/dy =velocity gradient
Where, du/dy =velocity gradient
µ= coefficient of viscosity, absolute
viscosity or dynamic viscosity.

28. Following Observations can be
Following Observations can be
made from Newton’s viscosity
made from Newton’s viscosity
Equation:
Equation:
• Max. shear stress occur when velocity
Max. shear stress occur when velocity
gradient is largest and shear stress
gradient is largest and shear stress
disappears where velocity gradient is zero.
disappears where velocity gradient is zero.
• Velocity Gradient becomes small with
Velocity Gradient becomes small with
distance from the boundary.Consequently
distance from the boundary.Consequently
the max value of shear stress occurs at
the max value of shear stress occurs at
the boundary and it decreases from the
the boundary and it decreases from the
boundary.
boundary.