This ppt is more useful for Civil Engineering students. I have prepared this ppt during my college days as a part of semester evaluation . Hope this will help to current civil students for their ppt presentations and in many more activities as a part of their semester assessments. I have prepared this ppt as per the syllabus concerned in the particular topic of the subject, so one can directly use it just by editing their names.

1. Venturimeter
It is a device, which is used for measuring the
rate of flow of fluid through a pipe.
It consists of an
• Inlet section followed by
• Convergent section
• A cylindrical throat and
• A gradually divergent cone.

2. Principle
The basic principle on which it works is that by reducing
the cross sectional area of the flow passage, a pressure
difference is created and the measurement of the pressure
difference enables the determination of the discharge
through the pipe.

3. OBJECT
1. TO CALIBRATE THE VENTURIMETER.
2. TO OBTAIN A GRAPH BETWEEN DISCHARGE
COEFFICIENT ‘K’ AND LOG10RE.

4. WORKING.
AS THE CROSS SECTION OF THE THROAT
IS SMALLER THAN THE CROSS
SECTIONAL AREA OF THE INLET SECTION,
THE VELOCITY OF FLOW AT THE THROAT
WILL BECOME GREATER THAN THAT AT
THE INLET SECTION, ACCORDING TO
CONTINUITY EQUATION.

5. THE INCREASE IN THE VELOCITY OF FLOW AT THE
THROAT RESULT IN DECREASE IN PRESSURE AT THIS
SECTION. AS SUCH A PRESSURE IS DEVELOPED
BETWEEN THE INLET SECTION AND THE THROAT OF
VENTURIMETER.
THIS PRESSURE DIFFERENCE CAN BE DETERMINED
EITHER BY CONNECTING DIFFERENTIAL
MANOMETER BETWEEN THE PRESSURE TAPS
PROVIDED AT THESE SECTIONS OR BY CONNECTING
THE SEPARATE PRESSURE GAUGE AT EACH OF THE
PRESSURE TAPS. THE MEASURE OF THE PRESSURE
DIFFERENCE BETWEEN THESE SECTIONS ENABLES
THE RATE OF FLOW OF FLUID TO BE CALCULATED.

6. THE CROSS SECTIONAL AREA OF THE THROAT
OF VENTURIMETER SHOULD NOT BE REDUCED
UNTO A CERTAIN LIMIT, OTHERWISE THE
PRESSURE AT THIS SECTION DROPS BELOW
THE VAPOR PRESSURE OF THE FLOWING
FLUID THAN THE FLOWING FLUID MAY
VAPORIZE AND THE VAPOR POCKETS MAY BE
FORMED IN THE LIQUID AT THIS SECTION.

7. THEORY
BY APPLYING BERNOULLI THEOREM
BETWEEN ENTRANCE AND THROAT
SECTIONS, THE RELATION FOR DISCHARGE
CAN BE DERIVED.Q = K
A√2g √∆h
√((D/d)4
-1)
= K.C. √∆h
Here, ∆h is the difference of piezometric.

8. HEADS BETWEEN ENTRANCE AND THROAT SECTION AND
IS KNOWN AS “VENTURI HEAD” C IS CALLED CONSTANT OF
VENTURIMETER AND DEPENDS UPON GEOMETRIC
PARAMETERS OF GIVEN VENTURIMETER AND K IS CALLED
DISCHARGE COEFFICIENT.
IT TAKES ONTO ACCOUNT THE ENERGY LOSS BETWEEN
TWO SECTIONS AND DEPENDS ON THE RE. USUALLY K
VARIES FROM 0.96 TO 0.99 FOR RE>105
. THE REYNOLDS NO
RE IS GIVEN AS U2 D/ =4 Q/ΠD
IS THE KINEMATIC VISCOSITY OF FLUID AND DEPENDS ON
THE TEMPERATURE.

9. EXPERIMENTAL SETUPEXPERIMENTAL SETUP
THE VENTURIMETER IS FITTED IN A PIPE
LINE, TO WHICH AN INLET VALVE IS
FITTED. THE PRESSURE TAPS ARE
PROVIDED AT ENTRANCE SECTION 1 AND
THROAT SECTION 2. A U-TUBE MERCURY
MANOMETER IS FITTED BETWEEN THESE
POINTS 1 AND 2. WATER TANK AND A
STOP WATCH IS USED TO MEASURE THE
DISCHARGE.

11. PROCEDURE
1. REGULATE THE INLET VALVE TO ALLOW A STEADY
FLOW THROUGH VENTURIMETER
2. COLLECT THE CERTAIN VOLUME OF WATER IN THE
TANK AND NOTE THE TIME T
3. NOTE THE MANOMETER READING IN THE LEFT
LIMB (H1) AND RIGHT LIMB OF MANOMETER (H2).
THIS DIFFERENCE IS X.
4. REPEAT THE STEPS 1 TO 3 FOR OTHER RATE OF
FLOW.
5. TAKE SEVEN TO EIGHT SETS OF READINGS

12. CALCULATIONSCALCULATIONS
1. THE VENTURIMETER CONSTANT C IS CALCULATED AS.
C = A√2G /√((D/D)4-1)
2. THE DISCHARGE Q IS THEN CALCULATED BY VOLUMETRIC
METHOD
3. THE DEFLECTION OF MERCURY MANOMETER X IS CONVERTED
INTO EQUIVALENT HEAD OF FLOWING LIQUID WATER)
H = X (SM/S - 1) = X (13.6/1 – 1 ) = 12.6XH
WHERE SM IS SPECIFIC GRAVITY OF MEASURING FLUID AND S
IS THE SPECIFIC GRAVITY OF WATER.
4. NOW THE SQUARE ROOT OF H IS DETERMINED.
5. THE DISCHARGE COEFFICIENT K IS CALCULATED.
K = Q/C√H
6. FINALLY THE RE IS CALCULATED CORRESPONDING TO
DIFFERENT SET OF DISCHARGES.

13. FORMULA USED
1. Q = K.HN
2. K = CD.A1.A2√2G
√(A1
2
-A2
2
)
WHERE ,
Q= DISCHARGE (RATE OF FLOW)
K= CONSTANT
H= DIFFERENTIAL HEAD
CD= COEFFICIENT OF DISCHARGE
A1= AREA OF INLET SECTION
A2= AREA OF THROAT SECTION
G= GRAVITATIONAL ACCELERATION
N= 0.5(APPR.)

14. OBSERVATION TABLES
TABLE 1
DISCHARGE MEASUREMENT TABLE
S.No. Area
of
collecting
tank
Depth Of Water collected Volume
of
water
collected
Time
of
collectio
n
Discharg
e
Q =
(A1∆h/t)
cumec
Initia
reading
Final
reading
depth
S.NO. Manometer reading Head
H cm
h½ K Re LogRe
I
Limb
II
Limb
Diff.
‘xcm
Table 2
Dia of pipe D=
Dia of throat d=
Area of collecting tank = A
Lab temperature = , kinematic viscosity = m2/sec

15. PRESENTATION OF RESULT
 PLOT A GRAPH BETWEEN Q AND √H ON AN ORDINARY
GRAPH. IT WILL BE A STRAIGHT LINE PASSING
THROUGH THE ORIGIN
 PLOT ANOTHER GRAPH BETWEEN K AND RE ON A SEMI
LOGARTHMIC GRAPH SHEET
 AVERAGE VALUE OF K =…..