List of Experiments Prescribed by RGPV, Bhopal

Fluid Mechanics Laboratory

Lab code- ME-405

MECH. ENGG. DEPARTMENT

Fluid Mechanics Laboratory

(CM-405)

List of experiments prescribed by RGPV, Bhopal

To determine the local point pressure with the help of pitot tube..
Calibration of Venturimeter.
Calibration of Open channel Flow Measuring Devices
Calibration of Orifice Meter.
Calibration of Nozzle meter and Mouth Piece.
Reynolds experiment for demonstration of stream lines & turbulent flow.
Determination of metacentric height.

EXPERIMENT NO.1

Pitot tube

Date of conduction:-

Date of submission:-

Submitted by other members:-

Group no:-

Signature

Name of faculty incharge:

Name of Technical Assistant:

Objective: -Calibration of Pitot tube and measurement of air velocity.

Theory: -APitottubeis apressure measurementinstrument used to measurefluidflowvelocity. The Pitot tube is used to measure the local velocity at a given point in the flow stream and not the average velocity in the pipe or conduit.As this tube contains fluid, a pressure can be measured; the moving fluid is brought to rest (stagnates) as there is no outlet to allow flow to continue. This pressure is the stagnation pressure of the fluid, also known as the total pressure.

Bernoulli's equation states:

Stagnation pressure = static pressure + dynamic pressure

Which can also be written

Solving that for velocity we get:

(1)

Where:

is fluid velocity;
is stagnation or total pressure;
is static pressure;
andis fluid density.

The value for the pressure drop–ordue to, the reading on the manometer:

(2)

Where:

is the density of the fluid in the manometer
is the manometer reading

And from equations (1) and (2)

(3)

Equation (3), can be used to measure fluid velocity, but For Pitot tube measurement, measurement error could be resulted due to certain reasons, errors may introduce in the measurement; that the probe is not aligned with the flow direction. At low Reynolds number, validity of applying Bernoulli equation should be investigated further. The geometry of the probe sting support affects the accuracy of measurement.

Therefore, calibration of pitot tube required, which can be done using a hot-wire anemometer. Considering the linear law

The pitot tube equation;

Here, K is pitot tube coefficient and needs to determine by calibration.

A heated wire of micro-meters in diameter and mini-meters inlength is inserted in the flow field. The flow velocity can be sensedbased on the principle of convective heat transfer concerning flowover a heated 2-D circular cylinder. In anemometer,the circuitry consists of a feedback loop of a Wheatstonebridge and a series of amplifiers which directly flow velocity.

Pitot tube is basically for time-mean velocity measurement (very low frequency response. It islow cost, easy to use.Hot-wire is basically for real-time velocity fluctuationsmeasurement (high frequency response).

Procedure:

Adjust air intake with the help of a valve, fix anemometer probe at the discharge of channel.
Connect manometer to the Pitot tube and piezo-meter tube.
Start the blower.
Take the flow rate reading anemometer and pressure drop in manometer.
Repeat the step 3 & 4 for unknown flow rate & record the reading in the tube and draw the graph.
The above procedure may also be repeated for difference in depth of Pitot tube.

Observation Table:-

S. no. / Anemometer reading, V / Manometer reading, ∆h / Actual velocity
V
1
2
3
4

Calculation:-Plot a graph velocity Vs head as shown and determine the slope of the line and coefficient of velocity of Pitot tube. Use linear regression to fit the equation.

K = slope/2g

Results: -

The pitot tube coefficient K =

Conclusion:-

Precautions:-

1.Do not close air regulating valve fully to avoid over loading at blower meter.

2.Use only mild detergents to clean the instruments do never use any organic solvent and strong acid or alkali.

3.Ground the instrument properly to avoid electric shock.

4.The density of fluid in manometer is one.

Suggestion

Further reading resources:

Book: Lab experiment related theory available in following books:

Book Name Author Page No.

1. Fluid mechanics Streeter 130-132,457-458

2. Fluid mechanics S.G Gupta 165-180

Web resources:

EXPERIMENT NO.2

Calibration of Flow Measuring Devices

Date of conduction:-

Date of submission:-

Submitted by other members:-

Group no:-

Signature

Name of faculty incharge:

Name of Technical Assistant:

Objective: -To calibrate following flow measuring devices.

Venturi meter,Orifice meter and Rotameter

Theory:

The flow rate in a closed channel is usually measured by creating a constriction in the cross-section of the channel and measuring the pressure drop caused by it. The drop in the pressure across the constriction depends on the flow rate and thus is a measure of the flow rate.

In case of a venturi meter, the flow cross-section of the channel rapidly decreases to a minimum at the venturi throat, and then gradually increases to the original cross-section. The difference of pressure between the pressure tapping 1 at the inlet to the device and the pressure tapping 2 at vena contract of slow stream which occurs almost at the venturi throat is measured by a U- tube mano-meter.

In case of the orifice meter the vena-contract occurs at approximately half a pipe diameter drown stream the orifice plate.

Assuming the flow to be incompressible and in-viscid between the inlet section 1 and the vena contract section 2, and assuming the flow be one dimensional, use of the continuity equation and the Bernoulli’s equation leads to the flow expression as

Where

A1 – The area at inlet side in cm2

A2 – The area at throat in cm2

∆h – Head difference in the manometer,

g – Acceleration due to gravity (9.81m/sec²)

Coefficient of discharge

Calibration of flowmeters-

Equations derived above relating flow rate to the differential pressure cannot be applied directly inpractical applications. All the flowmeters need calibration a priori where a known quantity of fluid ispassed through the flowmeter and the differential pressure across the flowmeter related to the actual massflowrate through a discharge coefficient given as the ratio of actual to theoretical mass flowrate. Twomethods of knowing the actual mass flowrate are- measurement of time for collection of a finite volumeof fluid and measurement of mass collected in a certain amount of time.

Description of Equipment:-

SPECIFICATIONS OF VENTURI METER:

Pipe Dia:25 mm ID

Throat Dia:12 mm

Distance of upstream pressure tap from the throat:___mm

SPECIFICATIONS OF ORIFICE METER:

Pipe Dia:25 mm ID

Orifice Dia:12.7 mm

Distance of upstream pressure tap from the throat:___mm

Size of collecting tank:24x24x40

Procedure:

Make a neat sketch of the experimental set-up and note/measure the necessary dimension on it.
Clean the storage tank fill with fresh water.
Open the bypass line and close the delivery line.
Keeping the valves to the venturi meter and the orifice meter closed, open the discharge line.
Slowly open the supply to the venturi meter. After the steady state is reached, read the manometer reading and determine the flow rate volumetrically. Also read the Rota meter reading. Repeat the experiment for higher flow rates, by increasing the supply slowly.
Lose supply to the venturi meter and slowly open supply to the orifice meter. Repeat the experiment as done In the case of venturi meter.
Repeat the procedure for at least ten mass flow rates for both venturimeter and orifice meter.

Observation Table:-for coefficient of discharge

Sl.
No / Time for 10cm rise of water level (s ) / Actual discharge Qa.cm3/s / Differential head in cm. of mercury / Differential head in cm. of water / Theoretical discharge Qth,cm3/s / Coefficient of discharge Cd
t1 / t2 / tm / h1 / h2 / h1-h2
=hHg

Calibration Table

Sl.
No / HHgin cm / Hwin cm / Qain cm3/s / Log Qa / Log HHg / Actual discharge
Qa=KHHgn / HHgin cm

Calculation:-

Calculate actual discharge through flow meter

Where

a – Area of measuring tank in cm2

h – Height differences in piezo meter in cm

t – Time to collect water for a height difference of h cm, measured in seconds

And Now calculate coefficient of discharge for each run

Calculations for Calibration curve

The equation

Qa = Cd x Qth can be written as

Where

Use linear regression to fit the equation and show on calibration curve, logQa vs logHHg and determine the slope of the line and coefficient.

Results: -

Conclusion:-

Precautions:-

1.Do not close air regulating valve fully to avoid over loading at blower meter.

2.Use only mild detergents to clean the instruments do never use any organic solvent and strong acid or alkali.

3.Ground the instrument properly to avoid electric shock.

4.The density of fluid in manometer is one.

Suggestions:-

Further reading resources:

Book: Lab experiment related theory available in following books:

Book Name Author Page No.

1. Fluid mechanics Streeter 467-470,230-251

2. Fluid mechanics S.G Gupta 165-180

3. Fluid mechanics Modi and seth 700-703

Web resources:

EXPERIMENT NO.4

Losses due to pipe fittings

Date of conduction:-

Date of submission:-

Submitted by other members:-

Group no:-

Signature

Name of faculty incharge:

Name of Technical Assistant:

Objective:-

(i)To determine the loss of head in the fitting at the various water flow rates.

(ii)To determine the loss coefficient for the pipe fittings.

Theory:-Loss of head due to change in cross section, bends, elbows, valves and fittings of all types fall into the category of minor loss in pipeline. In long pipe lines the friction losses all much longer than this minor losses and hence the fleeter and often neglected. But in shorter pipelines their consideration is necessary for the correct estimate of losses.

The minor loss in contraction can be express.

The minor loss due to enlargement can be expressed as.

Where,

h1 = minor loss or head loss

K1 = Loss coefficient

V1 = Velocity of fluid in pipe of small diameter

V2 = Velocity of fluid in pipe of larger diameter

Description:-

The apparatus consist of a ½” bent and elbow. A sudden expansion from ½ ” to 1” and a sudden contraction from 1” to ½ ” ball value and gate value pressure taping are provided at inlet and outlet of these fitting at suitable dust. A differential manometer in the lines gives pressure gauge due to fittings supply to the pipeline is made through centrifugal pump which deliver water from sump tank. The flow of water in pipeline is made through centrifugal pump which deliver water from is regulated by means of central valve and by pass valve discharge is measured with the beep of measuring tank and stop watch.

Utilities Required:

1.Power supply: single phase 220 volts, 50 Hz, 5 AMP. With earth

2.Water supply

3.Drain

STANDARD DATA:

A→ Area of measuring tank = 98.059 × 10-3m2

S→ Specific gravity of Hg= 13.6

g→ Acceleration due to gravity = 9.81 m/sec2

d→ Diameter of small pipe = 0.016 m.

d2→ Diameter of large pipe = 0.028 m.

a1→ Area of cross section of small diameter pipe = 2.0106 × 10-4m2.

A2→ Area of cross section of large diameter pipe = 6.1575 × 10-4m2.

Δh = 12.6 × h

Procedure:

A)STARTING PROCEDURE

Clean the apparatus and make all tanks from dust.
Close the drain.
Fill sump tank ¾ with clean water and ensure that no foreign particles an there.
Close all flow controls valves given on the water line and open by- pass valve.
Check the valve of Hg in manometer tube. It showed be to half. It is used then fills it.
Close all pressure tapes of manometer connected to different pipe fitting.
Ensure that ON/OFF switch given on the panel is at OFF position.
Now switch on the main power supply.
Switch on the pump.
Operate the flow control valve to regulate flow of water in the desired test section.
Open the pressure taps of manometer of related test section very slowly to avoid the blow of water on manometer fluid.
Now open the air release valve provided on the manometer. Slowly to release the air to manometer.
When there is no air in the manometer close the air release valves.
Adjust water flow rate in the manometer close the air release valves.
Record the manometer reading.
Measure the flow of water, discharge through desired test section using stop watch and the measuring tank.
Repeat same procedure for different flow rates of water, operating control valve and by pass valve.
When experiment is over for one desired test section, open the by-pass valve fully. The close the flow control valve of running test section and open the control valve of desired test section.
Repeat same procedure for selected test section and so on.

B) CLOSING PROCEDURE: