VERIFICATION OF BERNOULLI’S THEOREM
Aim:To verify the
validity of Bernoulli’s equation for incompressible flow
Introduction: A
fluid motion can be completely analyzed by the application ofcertain
fundamental equations. These equations are
1) the continuity
equation 2) the energy equation 3) the momentum equation.
The above three equations are
based on the three fundamental laws normally the law of conservation of mass
flow, the law of conservation of energy and the law of conservation of momentum
A fluid body can possess the
following types of energy namely potential energy, pressure energy and kinetic
energy.
Potential energy or Datum
energy: This is the energy possessed by a fluid body byvirtue
of its position or location in space. Suppose we consider a fluid of ‘W’ Kg at
a height of ‘Z’ in m above a datum plane. The potential energy of the fluid is
equal to W Z Kg-m. Thus, the potential energy per Kg of the fluid body is equal
to Z Kg-m per Kg or we say the potential head is Z in m.
Pressure energy:
This is the energy possessed by a fluid body by virtue of thepressure at which
it is maintained the pressure at the point is ‘P’ and w is specific
weight of the fluid
the pressure head is wP in m.
Kinetic energy:
This is the energy possessed by a fluid body by virtue of itsmotion. Suppose, a
fluid of ‘W’ Kg be moving at a velocity of ‘V’ m/ s.
Then,
Kinetic energy
of fluid =
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WV
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2
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N
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2g
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V 2
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Therefore,
Kinetic head =
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m
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2g
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Thus, we find that if a fluid
body of weight ‘W’ Kg be at a height of ‘Z’in m above a datum and at a pressure
intensity of ‘P’ Kg /m2 and at a velocity of
‘V’ m /s , then,
the total energy of the fluid body
æ
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P
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V
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2 ö
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= WçZ
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+
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+
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÷
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Kg-m
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ç
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w
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2g
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÷
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è
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ø
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æ
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P
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V 2
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ö
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The
total energy head = ç
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+
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+ Z ÷
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m
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ç
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w
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2g
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÷
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è
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ø
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Object:To verify
Bernoulli’s theorem (Law of Conservation of Energy )
Theory:
Bernoulli’s theorem is a form of the well known principle of conservation
ofenergy. The theorem is stated as “In a steady continuous flow of a
frictionless incompressible fluid, the sum of the potential head, the pressure
head and the kinetic head is same at all points. i.e.;
P1
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+
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V1
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+ Z1
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=
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P2
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+
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V2
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+ Z
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= ----------Constant
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w
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2g
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w
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2g
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2
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23
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1) The flow of the fluid is steady 2) The flow is frictionless
3)
The fluid is incompressible 4)The flow is
continuous
Description:
The present apparatus is a
self – contained unit operated on a closed circuit basis consisting of sump
tank, and supply tank. Collecting tank (delivery tank) connected to
Venturimeter with connections to piezometer tubes at different sections. A
constant steady supply of water with a means of mono block pump set with outlet
delivery valve for flow control. There is also provision for measurement of
flow rate thus, the velocity.
Procedure:
1)
Fill
in the sump tank with clean water, and add some quantity of coloured ink to it.
2)
Keep
the delivery valve open.
3) Switch
on the pump. Now, you will find water flowing to the collecting tank through
Venturimeter.
4) Now,
you find the different piezometric heads for corresponding points of
Venturimeter for constant supply head and delivery head.
5) Note
down all the piezometric readings and velocity head at particular point is also
noted separately by bringing the inserted probe to that point.
6)
Note
down height of water at supply tank and delivery tank
7) Change
the delivery head by pushing down the overflow pipe and repeat the experiment.
8)
Also,
change flow rate and repeat the experiment.
Observations:
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m2
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w = Specific Weight
of Water = 9810
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N/m3
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24
S.No No. of
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Area of
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Piezometer
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Water collected
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Time taken for
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Datum
Head
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Points
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points
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Reading
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in
collecting
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‘r’ rise of water
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tank
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‘i’
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‘Ai’
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P
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‘t’
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Z
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w
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‘r’
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UNIT
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m2
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cm
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m
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cm
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m
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sec
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cm
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m
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1.
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1.
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5.50x 10 -4
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2.
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2.
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4.75x 10 -4
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3.
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3.
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3.50x 10 -4
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4.
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4.
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2.50x 10 -4
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5.
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5.
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3.00x 10 -4
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6.
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6.
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3.50x 10 -4
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7.
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7.
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4.25x 10 -4
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8.
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8.
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4.70x 10 -4
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9.
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9.
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5.00x 10 -4
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Table of
Calculations:
S.No
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No. of
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Area of
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Discharge
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Velocity(V)
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Kinetic head
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Total
Head
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Points
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points
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p/w
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V=
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Q
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V 2
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P
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V 2
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+
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+ Z
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Ai
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‘i’
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‘Ai’
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Q
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2g
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w
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2g
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UNIT
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m2
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m3/sec
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m/sec
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m
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m
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1
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1
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5.50x 10 -4
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2
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2
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4.75x 10 -4
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3
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3
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3.50x 10 -4
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4
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4
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2.50x 10 -4
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5
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5
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3.00x 10 -4
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6
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6
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3.50x 10 -4
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7
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7
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4.25x 10 -4
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8
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8
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4.70x 10 -4
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9
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9
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5.00x 10 -4
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Graph:
The following curves are drawn on the same graph X-axis:
direct points (1, 2, 3, 4, 5, 6, 7)
Y-axis: pressure head, velocity head, elevation head
and total head
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