AE1256-aerodynamicslabmanuals

7/27/2019 AE1256-aerodynamicslabmanuals

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BLOWER BALANCE FOR SMALL ASPECT RATIO

SUMMARY:

The equipment has been designed as an experimental unit to study

the Co-efficient of Lift and Co-efficient of Drag for different aspect ratios of the

model. The test rig essentially consists of axial blower handling the air as the

medium of flow and is driven by AC Motor. The test rig has provisions for

varying the parameters, viz., speed, in turn flow and head. The specially

designed AC electric drive facilities the accurate calculations of input

horsepower to blower.

Aspect ratio = b2/s ; b = breadth of the model,

s = Area of the model(Span)

SPECIFICATIONS:

1.BLOWER TYPE : a) Axial with circular duct for (Delivery & Suction)

b) Operated at 60Hz.

2.MOTOR : AC Motor with thyristor speed controller (AC Drive)

3.DRIVE : AC. type

4.ELECTRICAL : Single ph, 220 V, AC supply with Neutral and

INPUT TO and Earth

THE CONSOLE


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PROCEDURE:-

1. Keep the model in testing area

2. Set the model to required angle up to 15()

3. Switch on the console

4. Switch on the blower motor and rotate the speed regulator knob to fullspeed

5. Note down the lift, drag & air velocity for zero angle of attack

6. Repeat the experiment for different angle of attack

Note: 1.During the adjustment of angle the direction of Angle is Positive

towards top and Negative towards down.

2. The Experiment is conducted using suction flow.

TABULAR COLUMN

Model Lift

in

Kg

Drag

in

Kg

Air

velocity

In

m/sec

Angle

of

attack

Coefficient

of Lift

CL

Coefficient

of Drag

CD


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DIAGRAM

(+)

b

C (-)

FORMULAE USED:

L

Coefficient of Lift CL = -----------------

()V2S

D

Coefficient of Drag CD = ----------------

()V2S

Where,

b = breadth of the model

= Density of air =1.1kg/m3S = Area of the model (Span)

V = Velocity of air m/sec

D = Drag force in Kg

L = Lift force in Kg


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TABLE OF READINGS AND CALCULATION:

SAMPLE CALCULATION:

L L = Lift force in Kg

Coefficient of Lift CL = ----------------- D = Drag force in Kg

1/2V2

S

0.94

= -------------------------------------- = 0.5930.5 1.1 (8)

2 0.49 x 0.1

V = Velocity of air m/sec

S = Span of the model=b x C

b = breadth of the model

BLOWER BALANCE

Velocity = 8 m/s

ModelAngle ofattack Lift Drag Span

Co-efficientof LiftCL

Co-efficientof DragCD

20 0.94 0.54 0.045 0.5934343 0.340909

15 0.88 0.5 0.045 0.5555556 0.315657

10 0.64 0.31 0.045 0.4040404 0.195707

5 0.48 0.23 0.045 0.3030303 0.145202

0 0.2 0.11 0.045 0.1262626 0.069444

-5-

0.18 0.12 0.045 -0.1136364 0.075758

-10-

0.34 0.19 0.045 -0.2146465 0.119949

-15 -0.53 0.28 0.045 -0.3345960 0.176768

SYMMETRICALAEROFOIL

-20-

0.85 0.47 0.045 -0.5366162 0.296717

20 0.03 0.13 0.049 0.0173933 0.075371

15 0.18 0.04 0.049 0.1043599 0.023191

10 0.16 0.08 0.049 0.0927644 0.046382

5 0.3 0.17 0.049 0.1739332 0.098562

0 0.56 0.32 0.049 0.3246753 0.185529

-5 -0.6 0.21 0.049 -0.3478664 0.121753

-10-

0.86 0.34 0.049 -0.4986085 0.197124

-15-

1.05 0.56 0.049 -0.6087662 0.324675

SYMMETRICALAEROFOIL

-20-

1.29 0.74 0.049 -0.7479128 0.429035


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C = Chord of the aerofoil

= Density of air = 1.1kg/m3

D

Coefficient of Drag CD = ------------

1/2V2

S

0.54

= -------------------------------------------- = 0.340

0.5 1.1 (8)2 0.490.1

GRAPHS:

HELE-SHAW APPARATUS

Hele-Shaw flow is produced by forcing a liquid through a thin gap

between parallel plates. An example of Hele-Shaw flow is provided inFig. for flow over an inclined plate. Streak lines are generated byintroducing dye at evenly spaced points upstream of the field of view.Since the flow is steady, the streak lines are coincident with streamlines.The fluid is water and the acrylic plates are 1.0mm apart.

Assumptions:1. The flow is steady.2. The flow is incompressible.

3. The flow model two-dimensional potential flow in the xy-plane.


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Analysis: When equally spaced streamlines of a stream function spreadaway from each other, it indicates that the flow speed has decreased inthat regain likewise, if the streamlines come closer together, the flow

speed has increased in that region. In Fig. we infer that the flow farupstream of the plate is straight and uniform, since the streamlines areequally spaced. The fluid decelerates as it approaches the underside ofthe plate, especially near the stagnation point, as indicated by the widegap between streamlines. The flow accelerates rapidly to very highspeeds around the sharp corners of the plates indicated by the tightlyspaced streamlines.Potential flow theory: This theory gives the definition of stream lines as

lines which shows the direction of the flow of fluid at any particularmoment. A flow entirely free from vortices or vorticity of any kind issaid to be irrotational or potential flow. The principle of superposition isalso defined on the basis of this theorem. The stream function for a flowdefined by superimposing two other flows upon one another is sum ofstream function of the two components of the flow. This is known asprinciple of superposition. The basic equation of potential flow theory isas follows.2 2

+ x2 y2Where is the stream function.

VOLUME FLOW RATE DEDUCTED FROM STREAMLINES

Water is sucked through a narrow slot on the bottom wall of a water

channel. The water in the channel flows from left to right at uniformvelocity ,the slot is perpendicular to the xy-plane, and runs along the z-axisacross the entire channel, which is w = 2.0m wide. The flow is thusapproximately turn two-dimensional in the xy-plane. Severalstreamlines of the flow rate plotted and labeled in Fig.

The thick streamline in Fig. is called the dividing streamline because itdivides the flow into two parts. Namely, all the water below this

dividing streamline gets sucked into the slot, while all the water above


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the dividing streamline continues on its way downstream. For the givenset of streamlines, we are to determine the volume flow rate through theslot and estimate the fluid speed at a point.

Analysis: By Fig., the volume flow rate per unit width between the

bottom wall (wall = 0) and the dividing streamline (dividing= 1.0 m2/s) is

V

dividing - wall = (1.0-0)m2/s = 1.0m2/s

w

All of this flow must go through the slot. Since the channel is 2.0m wide,the total volume flow rate through the slot is

VV = w = (1.0 m

2/s) (2.0m) = 2.0 m

3/s

w

To estimate the speed at pointA, we measure the distance between thetwo streamlines that enclose point A. We find that streamline 1.8 isabout 0.21 m away from streamline 1.6 in the vicinity of point A. Thevolume flow rate per unit width (into the page) between these twostreamlines is equal to the difference in value of the stream function. Wecan thus estimate the speed at pointA.

V 1 V 1 1

VA = = (1.8-1.6) = (1.8-1.6)m2/s = 0.95 m/s

w w 0.21 m

Our estimate agrees very well with the known free-stream speed (1.0m/s), indicating that the fluid in the vicinity of point A flows at nearlythe same speed as the free-stream flow, but points slightly downward.

The streamlines of Fig. were generated by superposition of a uniformstream and a line sink, assuming irrotational (potential) flow. Wediscuss such superposition.

Inlet valve

Drain valve inlet valve ( ink)


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Air out valve

Width of the test channel is 0.30 m

Gap of the test channel is 4 mm = 0.4cm = 0.04 m

Connect the inlet valve side to water source. Fix the aero foil (or any

other) model. Fill the die liquid in the funnel.

Keep air out valve, drain valve and inlet valve (ink) in closed position.By operating air out valve fill the gap test place with water. (Removal of

100 % air gap is not possible). Close the outlet valve.

Airs out has to be made by opening the air out valve and then close the

valve.

Inlet and outlet valve are to be opened partially (by experience) to get

proper flow pattern. Open inlet valve (ink) such a way the colors should

start in the straight line form. If required adjust inlet and outlet valve.

Observe thick line of 1 mm in upper side which has to be noted by

operator.

Any two stream light lines to be identified and note down the scale

reading (the operation to be fast). Also observe the eddy formation.

Collect 200 ml of water against time.

Close inlet valve and open outlet fully to drain the water.

Repeat the experiment for other models.

After the experiment see that the die line & the passage of 4 mm to be

cleaned by flushing the water. Clean water to be used to avoid clogging.


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SUBSONIC WIND TUNNEL

INTRODUCTION :

The information useful for solving aerodynamic problems

of Aeronautical, Space , Automobile and Civil Engineering structures, are

best obtained rapidly , economically and accurately by testing the scaled

models, and sometimes actual structure in Wind Tunnels .The size, thespeed and other environmental conditions of tunnel are determined by the

actual users problems .

Leaving the size and environmental to the actual users, the speed

determines the type of the tunnel namely, subsonic ( low speed ),Near-

sonic, Transonic, Super-sonic and Hyper-sonic. While the speeds of these

tunnels are obviously named with reference to the sonic ( sound ) velocity ,

the low speed ( subsonic ) tunnel which is of our concern is below 300 mph.

An alternative definition to the low speed tunnel would be the tunnel where

the compressibility of Air is negligible .

SPECIFICATIONS :

* TYPE OF TUNNEL : Low speed, Open circuit,

Suction type.

* TEST SECTION SIZE : 300 mm x 300 mm.

* CONTRACTION RATIO : 9 : 1


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* DRIVE : Axial Flow fan driven by AC

Motor (10 Hp)

with AC Drive for Speed Controlling

* POWER REQUIREMENT : AC. 3 ph, 440 V, 32 Amps

Electrical supply with Neutral & Earth

connection.

* MATERIAL OF Effuser, Diffuser : FRP

CONSTRUCTION : Blower Frames &

Supporting Frame: Mild Steel.

SPECIAL FEATURES:

* Tunnel does not need any civil work and easily transportable to any

place of convenience.

EXPERIMENTAL CAPABILITIES:

* Study of Lift, Drag & Side Forces : Symmetric, Cambered.

on Aerofoil

* Study of Drag on : Wedge, Flat Disc,

Bluff Bodies Automobile models.

* Study of Pressure Distribution : Symmetrical Aerofoil,

Unsymmetrical Aerofoil,

Smooth Cylinder

* Study of Smoke Pattern : Aerofoil, Cylinder,

Sphere & Hemisphere.


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MAIN PARTS:

Honeycomb inlet mesh screen, Effuser, Blower unit with ACmotor and thyristor controller, Three component like Lift, Drag, Side force

balances, Multi - tube manometer , Smoke generator constitute the complete

tunnel .

DESCRIPTION:

A. INLET DUCT (Effuser):It is aerodynamically contoured section with contraction area ratio

9: 1. The inlet starts with dimension of 900mm x 900mm contoured to

300mm x 300mm. The axial and lateral turbulence are reduced and smooth

flow of air entering the section is achieved by installing the Honey-combs

and screens , for most effectiveness of the air inlet . The ratio of length to

cell size of the Honey -comb is maintained as per the recommended

standards . The wire mesh is also fixed to smoothen the flow , futher . Thisis particularly useful for obtaining laminar flow. The screen is made removable

for possible cleaning. The duct is secured to the test section by flange. The

provision is also made for easy removal of Effuser and diffuser for

possible separation from the test section when required. It is also highly

smoothened and painted.

B. TEST SECTION:The central portion of the test section sandwiched

between the inlet duct ( Effuser ) and the diffuser using flange. It has

300mm x 300mm cross section (inside ) and 550mm length . Fixed with

transparent window on either side which facilitates fixing and viewing of

the models. This houses smoke chest fixing points.


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The traversing mechanism is fixed on its top of the movement of total

pressure probe .The holes provided for holding the models for different

studies and for taping out the pressure probes .

C. DIFFUSER:

The downstream portion of the tunnel is the diffuser .To

the end of this is attached an axial flow fan . The diffuser starts with

300mm x 300mm square section at the test section end and enlarges to

900mm diameter round at the fan driven end . It is flanged and bolted to the

test section.

D. AXIAL FLOW FAN UNIT:

The fan unit is independent stand alone type and does not

require any foundation . It is housed in rounded casing which is secured

to the diffuser . The bladed rotor is connected to AC motor directly coupled.

E. CONTROL CONSOLE:

The tunnel has two consoles, one for the air speed control (

AC motor Controller ) and the other for the indication of velocity head

and forces . The console which houses tyhristor speed controller

connected to AC motor by 3 ph, 440 V, AC supply . All safety precaution for

excessive electrical loading are provided.

F. ATTACHMENTS:

( i ) STRAIN GAUGE BALANCE :

This is housed beneath the test section portion. The

models are mounted on the vertical mechanical member called String. The

lift drag & side forces are measured using this unit.


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(ii) MULTI BANK MANOMETER:

This manometer is used for studying the pressure

distribution across the various models. This unit is mounted to the right of the

test section.

INSTALLATION:

The tunnel does not require any civil work whatsoever , and is

completely self reacting stand alone type .

Normally , the first time installation of the tunnel is done by

our experienced engineers , unless it is required to be re-installed in another

place . In the event of reinstallation, the assembly of the tunnel is to be

done by following the description explained in earlier pages .While installing the tunnel, the following things are to be borne in mind.

It is recommended to install the tunnel facing the inlet and the

exhaust ( blower side ) of the tunnel towards the windows . This is to

facilitate clear movement of air velocity at the test section and also

pushing out the smoke during the flow visualization experiment using

smoke generator .

The electric power supply to the control panel should be accordingto the specification .

PREPARATIONS & OPERATIONS:

a) WIND TUNNEL BALANCE :

The tunnel balance is three component type ( three forces )

designed using the electrical strain gauges to indicate separately on the

digital indicator. The balance is intended for indicating the Lift , Drag, Side

forces in case of aerofoils, and drag force only in case of bluff bodies,Viz.,

spherical, Hemi - spherical, Flat disc. These models are mounted on the string

(Vertical square rod) situated exactly beneath the test section. The output from


14/48

the Lift, Drag, Side forces are connected to the respective multi - pin sockets

provided at control panel.

b) SMOKE GENERATOR:

The smoke generator unit is used for producing the dense white

smoke , for the purpose of flow visualization across the models .

Essentially , it consists of electrical cartridge heater , over head diesel

bottle , sump bottle , air supply pipe from blower and smoke distributor .

Keep the needle valve closed. Fill the over head bottle with diesel

and check the level . Fix the smoke distributor at the starting portion of

the test section . Connect the hose pipe of the distributor to the smoke

generator. Connect the electrical supply of the cartridge heater .Fix the

required model in the test section, cover the back side of the test section

with the black cloth . Connect the air inlet to the smoke generator. Initiallyopen the needle valve and allow the diesel to pass through the heater

(Thus soaking the heater unit) to the sump bottle . Now switch ON the heater

control unit and keep it at maximum . After the initial heating is done the

smoke starts coming out of the smoke distributor. Now decrease the heating

and balance

the heating & the diesel drip in such a way that the continuous dense

smoke starts coming out of the distributor . ( If more smoke has to be

forced out of the distributor , the air inlet pipe of the smoke generator may

be connected to air compressor unit , where higher forcing pressure is

available ) . Switch ON the blower ,adjust the valve to get the uniform &

visible smoke across the models . The unused diesel collected in the sump

bottle may be put back to over head bottle .


15/48

After the experiment is over, close the needle valve , switch

OFF the heater , controller , and allow the blower to run for sometime to

drive out unused smoke .

During the experiment check blockage of condensed oil in the

smoke outlet pipe leading to the distributor and drain it to the sump bottle .

c) MULTI TUBE MANOMETER:

This is used for studying pressure distribution across

various models, Viz., Aerofoil, cylinder, special purpose shapes . It contains

13 Nos. Of tubes mounted on board with adjustable inclination. Bottom of alltubes are interconnected and in turn to the balancing reservoir filled with

coloured water . While the last tube is left open to atmosphere for

reference , all other 12 tubes are connected at their top to pipe / tube

bundles of the model. The required model is held in the test section

between holes provided front and back side Perspex windows. The

pressure tapings ( tube outlets ) are connected to the glass limbs of the

respective Serial Number . The required degree of angle of inclination canbe given to the tube bundle and angle measured with respect to the

horizontal .

d) VELOCITY INDICATOR, PITOT TUBE & TRAVERSE UNIT:The velocity of air at test section is measured as the

m/sec in digital manometer. The two plastic pipes from the indicator are to

be connected to pitot tubes ( static and total heads ports ). Check that thetotal head port always faces the direction of flow . Otherwise the direction

effect may cause error in air velocity reading .The traverse unit can be

operated up and down the test section . It should show zero reading when

the pitot tube head probe is in bottom most position of the test section .

Otherwise adjust the pointer.


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OPERATING INSTRUCTIONS:

All the components described under DESCRIPTION are

readily integrated for conducting the various experiments . Follow the

general instruction detailed below.

1. Connect the power card to the 400 V, 32 A,3ph, AC power

supply with neutral and earth connection .

2. Keep the speed controller knob at Min.

3. Check all the switches of the controller are in OFF position

before starting .

4. Put-on the mains and observe the main indicator lights are

ON at the bottom of the control panel .

5. Now switch on the console and observe the console light in ON.

6. Select particular experiment & fix the required model in the test

section.

7. Follow the instruction for PREPARATION & OPERATION of

different attachments / accessories explained in earlier pages

.

8. Observe that no tools or loose parts are left in the test section, and

then close the transparent window.

9. Now increase the speed control knob slowly in the clock-wise

direction and observe the AC Motor picking up the speed

gradually.

10. Observe the movement of manometer liquid in inclined

manometer (velocity indicator) when liquid variation is low

set the required value of air velocity by adjusting the knob

on the AC drive.

11. Take readings in the respective experiments detailed in

later pages

12. While stopping, gradually decrease the speed and then switch

OFF the AC motor controller.


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TROUBLE SHOOTING:

1. DC motor does not start:

a) Main not ON.

b) Console not ON.

c) Controller not ON.

d) Motor fuse blown off.

e) Field fuses blown off.

f) Mains fuse in your laboratory blown off.

2. Smoke does not appear out of distributor:a) Heater not ON.

b) No diesel in overhead bottle.

c) Diesel control valve closed.

d) Heater burnt / damaged.

e) Diesel supply too fast.

f) Air velocity too high, the smoke gets diffused.

g) The holes in diesel air pipes are blocked if so, take out the till

it and clean.

3. Digital Lift, Drag, Side forces and Yawing, Pitching, Rolling moments

indicators not getting balanced and does not show proper reading:

a) Multi-pin connector not properly connected to strain gauge balance.

b) The model or model fixing tube is touching the tunnel wall.

c) Calibration is to be done.

4. Pressure Distribution in multi-bank manometer bank is not indicatedproperly:

a) The holes in models are blocked. If so, clean it with fine gauge

S.S.wire supplied.

b) The air velocity is too low.

c) The angle of inclination of manometer bank is very high with

respect to horizontal.


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d) The air is leaking through the connecting tubes at the model

terminals or at some other point in the tube line.

EXPERIMENT CONDUCT:

A. ON PRESSURE DISTRIBUTION OF AEROFOIL & CYLINDER:

1. Fix the aerofoil in the test section.

2. Set the require angle of attack using angle setter.

3. Connect pressure tube bundle coming from the multi tube

manometer to the steel tube extensions of the aerofoil model,

follow the instruction mentioned under PREPARATION &

OPERATION.

4. Set the required inclination of the manometer angle.

5. Now set the required velocity of air flow using AC motor

controller knob, and now observe the displacement of manometer

liquid in all tubes standing at different levels, and note down the

readings.

B. ON FORCE CHARACTERISTICS:

(i) SPHERICAL, HEMI - SPHERICAL, DISC MODELS:

1. Fix the above models in the vertical sting & lock it.

2. Set the force and moment indicators to zero.

3. Fix the air velocity using the velocity indicator.

4. Take down reading of all forces and moment.

5. These models can be tested at different orientations & the

results are compared.

C. ON FLOW VISUALISATION:

1. Cover the back side of the test section with dark cloth.

2. Switch ON the light.

3. Follow the instructions under PREPARATION &

OPERATION to set up the experiment for flow visualization.


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4. Fix the required model in the test section, at required

orientation.

5. Now observe the smoke being forced out of the smoke

distributor at the entry to the test section.6. Control the main flow of air in test section by controlling the

AC motor speed, so that the smoke flow pattern to persist across

the model. Higher velocities will defuse the smoke.

7. Observe the flow pattern at different orientation of models.

8. Check periodically that adequate amount of diesel oil is

available in the over head bottle.

9. Also check the unbumt diesel oil being collected in the sumpbottle, and outlet smoke pipes and transfer it back to over head

bottle.

10. Never switch on the heater for long time without the diesel oil

being supplied to the unit.

11. After the experiment, switch off the heater, diesel supply and light

and run the DC motor for sometime. This is just to exhaust out any

smoke left in the tunnel.

THINGS TO REMEMBER:

1. Do not clean transparent test section windows with petrol,kerosene or other chemical detergents just use soap water.

2. Keep always the holes of the pressure distribution models closed

with soft clean paper wrapped round with rubber band. This is

very important because making holes on aerofoil is done by special

process and not easily be cleaned or made.3. In case of faults beyond routine repair / understanding, please write

to the manufacturer.

4. Dont bring any fire near the smoke generator during flow

visualization experiment.


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TABLEOFREADINGSO

NAIRFOIL

VALUESOFPRESSURE

CO-EFFICIENTONSYM

METRICALAIRFOIL

(1)to(6)

-

UpperSurface

(7)to(12)

-

LowerSurface

Velocity(V)-

(PoP)

-

InitialManometerReading

(P13P(i))/

2

Cp(i)

-

---------------------

Cp(i)=

Pressureco-efficientatdifferen

t

(PoP)

OBSERVATION

TABLE:

LOCATION

(X/C)

ANGL

EOFATTACKindegrees

0

5

10

15

20

-5

-10

-15

-20

1(5)

2(15)

3(15)

4(15)

5(20)

6(20)

7(10)

8(20)

9(20)

10(15)

11(15)

12(15)

13(StaticP)


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TABLEOFREADINGSO

NAIRFOIL

VALUESOFPRESSURE

CO-EFFICIENTONUNS

YMMETRICALAIRFOIL

(1)to(6)

-

UpperSurface

(7)to(12)

-

LowerSurface

Velocity(V)-

(PoP)

-

InitialManometerReading

(P13P(i))/

2

Cp(i)

-

---------------------

Cp(i)=

Pressureco-efficientatdifferen

t

(PoP)

OBSERVATION

TABLE:

LOCATION

(X/C)

ANGL

EOFATTACKindegrees

0

5

10

15

20

-5

-10

-15

-20

1(5)

2(15)

3(15)

4(15)

5(20)

6(20)

7(10)

8(20)

9(20)

10(15)

11(15)

12(15)

13(StaticP)


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VALUESOFPRESSURE

CO-EFFICIENTONCYLINDERMODEL

(1)to(6)

-

UpperSurface

(7)to(12)

-

LowerSurface

AtAirVelocity(V)-

(Ps-Po)

Pi=(Pr-Pm)

Cp=

-----------------

Cp=Pre

ssureco-efficient

Ps=(Pi3)

(1/2rV2)

------------------

2

TunnelDynamicPressureofW

aterPo=Pr-P13

OBSERVATION

TABLE:

LOCATION

Smoothcylindersurface

pressurePm

1(5)

2(15)

3(15)

4(15)

5(20)

6(20)

7(10)

8(20)

9(20)

10(15)

11(15)

12(15)

13(StaticP)


23/48

TABLEFORLIFT,DRAG

&SIDEFORCEREADINGSONSYMMETRICAL

AIRFOIL

AtVelocity:

Model

Angleof

Attack

Velocit

y

Liftforce

DragForce

Sideforce

Chord(C)=0.1m

Span(S)=0.25m

A=S*C=0.025m

2

=1.29kg/m

g=9.81m/sec

2

D=Drag(Kgf)

L=Lift(Kgf)


24/48

TABLEFORLIFT,DRAG

&SIDEFORCEREADINGSONUNSYMMETRIC

ALAIRFOIL

AtVelocity:

Model

Angleof

Attack

Velocit

y

Liftforce

DragForce

Sideforce

Chord(C)=0.1m

Span(S)=0.25m

Area(A)=S*C=0.025m

2

=1.29kg/m3

g=9.81m/sec

2

D=Drag(Kgf)

L=Lift(Kgf)


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STUDYOFFORCESON

BLUFFBODIES

AtAirVelocity:

Model

Drag

Projected

Dimension

inm

Projected

Areainm

2

CD

CircularDisc

0.12

113X10-4

Sphere

0.1

7.85X10-3

Hemispherical

Bowl

0.1

7.85X10-3

,CD=FA/FT

=(Actualmeasurementofforce)/(Theoreticalmeasurementofforce)


26/48

FORMULAE USED:

1) PRESSURE DISTRIBUTION OVER AN AEROFOIL:

P13 P(i)/(2)1/2

CP(i)= ---------------------

(PO P)

Where, P13 = Ps = static pressure in cm

From manometer (13th

point)

P(i) = Pressure at each point in cm

(Po P) = initial manometer reading in cm

Draw graph of

Pressure in mm of water Vs Pressure tapping points location distance

2) CO-EFFICIENT OF LIFT (CL) AND CO-EFFICIENT OF DRAG (CD) OF MODELS

FORCE, FT = AV2

x Cos 9.812g

where, A is projected area of aerofoil is the air density = 1.29 kg/m3g is acceleration due to gravity = 9.81 m/sec

2

v is velocity of air in m/sec

is angle of inclination on aerofoil

FA Actual measurement of force

CS, CL, CD = -------- = ----------------------------------------

FT Theoretical measurement of force

Draw graph of CL, CD Vs Angle of attack


27/48

3) VELOCITY OF AIR AT SECTION,V :

V = (2 x g x (hw/1000) x (w/

a 1))1/2

= (2 x 9.81 x (hw/1000) x (1000/1.29 1))

1/2

= 4.22 (hw)1/2

Where, w = 1000 kg/m3a = 1.29 kg/m3g = 9.81 m/s

2

hw= U tube manometer reading in mm

X

LocationX/C

1 0.05

2 0.2

3 0.35

4 0.5

5 0.76 0.9

7 0.9

8 0.7

9 0.5

10 0.35

11 0.2

12 0.05

X

Location

Distance

b/wPoints

1 5

2 20

3 35

4 50

5 70

6 90

7 -90

8 -70

9 -50

10 -35

11 -20

12 -5


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28

VELOCITY DISTRIBUTION OVER THE TEST SECTION

CHART OF FREQUENCY AND VELOCITY

Table of Readings

VALUES OF PRESSURE CO-EFFICIENT ON SYMMETRICAL

AIRFOIL

(1) to (6) - Upper Surface

(7) to (12) - Lower Surface

Velocity (V) - 64.1 m/s(Po P ) - dynamic head from velocity indicator (Velocity head) = 23.07

Frequency

Distance

travelled

in mm

Velocity

(from meter

)

0 42.650 55.6

100 64.5

150 64.5

200 64.1

250 58.5

50

295 56.5

0 27

50 32.4

100 40.5

150 40.5

200 40

250 38.4

30

295 35

Distancetravelled

Frequency Velocity

10.88 5.9

20.18 11.8

30.08 18.5

40 25.3

150

50 32.9


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29

(P13 P(i)) / 2Cp(i) - --------------------- Cp(i) = Pressure co-efficient at

different X/C location.

( Po P )OBSERVATION TABLE:

LOCA

TION

ANGLE OF ATTACK in degrees (SYMETRICAL MODEL)

Air Velocity =64.1 m/s

Cp(i) 0 Cp(i) 5 Cp(i) 10 Cp(i) 15 Cp(i) 20 Cp(i) -5 Cp(i)

1(5) -0.279 42.8 -0.628 53 -1.16 68.5 -1.56 80.8 -0.19 38.2 0.21 23.5 0.40

2(15) -0.208 40.5 -0.337 43.5 -0.50 46.8 -0.59 49 -0.17 37.7 0.05 28.9 0.17

3(15) -0.190 39.9 -0.267 41.2 -0.36 42.5 -0.39 42.7 -0.20 38.6 -0.02 31.2 0.06

4(15) -0.147 38.5 -0.199 39 -0.25 38.6 -0.22 37.2 -0.19 38.4 -0.05 32 0.03

5(20) -0.046 35.2 -0.064 34.6 -0.07 33 -0.01 30.3 -0.19 38.3 0.00 30.5 0.046(20) 0.071 31.4 0.067 30.3 0.09 27.8 0.08 27.2 -0.17 37.5 0.04 29.1 0.05

7(10) 0.101 30.4 0.083 29.8 0.10 27.5 0.07 27.5 -0.07 34.5 0.09 27.5 0.05

8(20) 0.021 33 0.046 31 0.11 27 0.12 26 0.05 30.4 -0.02 31.2 -0.08

9(20) 0.006 33.5 0.052 30.8 0.15 25.8 0.18 23.9 0.15 27.1 -0.07 32.8 -0.13

10(15) -0.034 34.8 0.049 30.9 0.18 24.6 0.24 22 0.22 24.8 -0.17 36.1 -0.26

11(15) -0.123 37.7 0.012 32.1 0.21 23.8 0.29 20.3 0.29 22.5 -0.34 41.6 -0.46

12(15) -0.129 37.9 0.107 29 0.38 18.2 0.48 14.1 0.48 16.4 -0.57 49.1 -0.89

13 33.7 32.5 30.6 29.9 32.1 30.5


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30


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31

VALUES OF PRESSURE CO-EFFICIENT ON SYMMETRICAL

AIRFOIL



Velocity (V) - 40.0 m/s

(Po P ) - dynamic head from velocity indicator (Velocity head) = 8.98



( Po P )OBSERVATION TABLE:

LOCAT

ION

ANGLE OF ATTACK in degrees (SYMETRICAL MODEL)

Air Velocity = 40.0 m/s


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1(5) -0.102 20 -0.551 25.5 -1.11 31.4 -1.29 34.2 -0.18 20.3 0.24 14.5 0.42

2(15) -0.087 19.8 -0.284 22.1 -0.50 23.7 -0.49 24 -0.16 20 0.08 16.6 0.20

3(15) -0.118 20.2 -0.236 21.5 -0.40 22.4 -0.35 22.3 -0.17 20.1 0.01 17.5 0.08

4(15) -0.095 19.9 -0.181 20.8 -0.28 20.8 -0.19 20.2 -0.17 20.1 -0.02 17.9 0.065(20) -0.024 19 -0.047 19.1 -0.11 18.7 0.00 17.8 -0.18 20.3 0.03 17.2 0.07

6(20) 0.071 17.8 0.071 17.6 0.04 16.8 0.10 16.5 -0.17 20.1 0.06 16.9 0.06

7(10) 0.102 17.4 0.102 17.2 0.07 16.4 0.10 16.5 -0.11 19.4 0.07 16.7 0.04

8(20) 0.016 18.5 0.063 17.7 0.06 16.5 0.13 16.2 0.00 18 -0.03 18 -0.06

9(20) 0.008 18.6 0.079 17.5 0.10 16 0.20 15.3 0.12 16.5 -0.06 18.3 -0.12

10(15) -0.039 19.2 0.079 17.5 0.14 15.5 0.26 14.5 0.20 15.5 -0.15 19.5 -0.23

11(15) -0.158 20.7 0.039 18 0.17 15.2 0.32 13.8 0.25 14.8 -0.31 21.5 -0.50

12(15) -0.213 21.4 0.047 17.9 0.34 13 0.50 11.5 0.45 12.3 -0.51 24.1 -0.79

13 18.7 18.5 17.3 17.8 18 17.6


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33

VALUES OF PRESSURE CO-EFFICIENT ON UNSYMMETRICAL

AIRFOIL




(Po P ) - Dynamic head from velocity indicator (Velocity head) = 23.07



( Po P )

OBSERVATION TABLE:

LOCAT

ION

ANGLE OF ATTACK in degrees (UNSYMETRICAL MODEL)


Cp(i) 0 Cp(i) 5 Cp(i) 10 Cp(i) 15 Cp(i) 20 Cp(i) -5 Cp(i) -1

1(5) 0.601 13.2 0.215 24.5 -0.18 36.5 -0.63 50.3 -1.08 64.1 0.63 11.5 0.55 12

2(15) -0.113 36.5 -0.389 44.2 -0.61 50.5 -0.79 55.7 -0.93 59.3 0.02 31.4 0.04 2

3(15) -0.319 43.2 -0.475 47 -0.58 49.3 -0.67 51.5 -0.66 50.5 -0.21 38.8 -0.18 36

4(15) -0.221 40 -0.346 42.8 -0.41 43.8 -0.42 43.5 -0.32 39.3 -0.20 38.5 -0.20 36

5(20) -0.138 37.3 -0.202 38.1 -0.20 37 -0.16 34.9 -0.04 30.4 -0.17 37.4 -0.20 3

6(20) 0.009 32.5 0.003 31.4 0.05 29 0.08 27.3 -0.02 29.8 -0.08 34.5 -0.16 35

7(10) 0.162 27.5 0.144 26.8 0.15 25.5 0.16 24.7 0.12 25.2 0.06 30 -0.13 34

8(20) 0.135 28.4 0.147 26.7 0.19 24.3 0.21 22.8 0.21 22 -0.07 34.4 -0.15 35

9(20) 0.141 28.2 0.184 25.5 0.25 22.5 0.29 20.5 0.31 19 -0.12 36 -0.10 33

10(15) 0.101 29.5 0.175 25.8 0.26 22 0.32 19.3 0.35 17.5 -0.16 37.2 -0.08 3

11(15) -0.061 34.8 0.083 28.8 0.22 23.4 0.32 19.5 0.36 17.3 -0.20 38.5 -0.11 3

12(15) -0.748 57.2 -0.276 40.5 0.12 26.5 0.38 17.3 0.52 12 -0.18 38 -0.10 33

13 32.8 31.5 30.5 29.8 29 32 30


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34

VALUES OF PRESSURE CO-EFFICIENT ON UNSYMMETRICAL

AIRFOIL




(Po P ) - Dynamic head from velocity indicator (Velocity head) = 8.98

(P13 P(i)) / 2Cp(i) - --------------------- Cp(i) = Pressure co-efficient atdifferent X/C location.

( Po P )

OBSERVATION TABLE:

LOCA

TION

ANGLE OF ATTACK in degrees (UNSYMETRICAL MODEL)



1(5) 0.496 12 0.260 14.8 -0.13 19.5 -0.60 25.1 -1.03 30.4 0.59 10.5 0.57

2(15) -0.110 19.7 -0.331 22.3 -0.55 24.8 -0.76 27.1 -0.88 28.5 0.04 17.5 0.06 1


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3(15) -0.299 22.1 -0.433 23.6 -0.54 24.7 -0.63 25.5 -0.67 25.8 -0.20 20.5 -0.09 1

4(15) -0.244 21.4 -0.307 22 -0.38 22.6 -0.39 22.4 -0.38 22.1 -0.17 20.1 -0.13 1

5(20) -0.165 20.4 -0.189 20.5 -0.18 20.1 -0.16 19.5 -0.04 17.8 -0.16 20 -0.15 1

6(20) -0.016 18.5 0.008 18 0.04 17.3 0.08 16.5 0.06 16.6 -0.08 19 -0.10 1

7(10) 0.142 16.5 0.142 16.3 0.09 16.6 0.17 15.4 0.14 15.5 -0.01 18.1 -0.12 18(20) 0.039 17.8 0.158 16.1 0.19 15.4 0.22 14.7 0.24 14.3 -0.10 19.3 -0.13

9(20) 0.142 16.5 0.189 15.7 0.25 14.6 0.28 14 0.31 13.4 -0.09 19.2 -0.16 1

10(15) 0.102 17 0.181 15.8 0.26 14.5 0.32 13.4 0.36 12.7 -0.09 19.2 -0.06

11(15) -0.118 19.8 0.079 17.1 0.21 15.1 0.32 13.5 0.39 12.4 -0.14 19.8 -0.10 1

12(15) -0.473 24.3 -0.221 20.9 0.13 16.1 0.40 12.4 0.51 10.8 -0.13 19.6 -0.10 1

13 18.3 18.1 17.8 17.5 17.3 18 1


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36

VALUES OF PRESSURE CO-EFFICIENT ON CYLINDER MODEL

(SMOOTH SURFACE)

(1) to (6) - Upper Surface (7) to (12) - Lower Surface

At Air Velocity (V) - 64.1m/s (Ps-Po)

Pi = (Pr - Pm) Cp = ----------------- Cp =

Pressure co-efficient

Ps = (Pi3) ( 1/2rV2 )------------------

2

Tunnel dynamic Pressure in cm of Water Po = Pr - P13

Reference Pressure Pr = 10

OBSERVATION TABLE:

LOCATION

P

Smooth

Cylinder

Surface Pm

Pressure Pi

in cm

Pressure

Ps in cmPs-Po Cp

1 29.8 -19.8 -17.127 0.373 0.0001

2 30.5 -20.5 -17.7325 -27.7325 -0.0105

3 34 -24 -20.76 -30.76 -0.0116

4 35.2 -25.2 -21.798 -31.798 -0.0120

516.4 -6.4 -5.536 -15.536 -0.0059

6 7.9 2.1 1.8165 -8.1835 -0.0031

7 20.8 -10.8 -9.342 -19.342 -0.0073

8 36.5 -26.5 -22.9225 -32.9225 -0.0124

9 32.5 -22.5 -19.4625 -29.4625 -0.0111

10 31.9 -21.9 -18.9435 -28.9435 -0.0109

11 33.8 -23.8 -20.587 -30.587 -0.0115

12 33.5 -23.5 -20.3275 -30.3275 -0.0114

13 27.5

VALUES OF PRESSURE CO-EFFICIENT ON CYLINDER MODEL

(SMOOTH SURFACE)

(1) to (6) - Upper Surface (7) to (12) - Lower Surface

At Air Velocity (V) - 40.0 m/s (Ps-Po)

Pi = (Pr - Pm) Cp = ----------------- Cp =

Pressure co-efficient

Ps = (Pi3) ( 1/2rV2 )------------------

2

Tunnel dynamic Pressure in cm of Water Po = Pr - P13


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37

Reference Pressure Pr = 10

OBSERVATION TABLE:

LOCATION

P

Smooth

CylinderSurface Pm

Pressure

Pi in cm

Pressure

Ps in cm Ps-Po Cp

1 19 -9 -7.785 -1.285 -0.0012

2 18.5 -8.5 -7.3525 -17.3525 -0.0168

3 18.2 -8.2 -7.093 -17.093 -0.0166

4 18.4 -8.4 -7.266 -17.266 -0.0167

5 12.5 -2.5 -2.1625 -12.1625 -0.0118

6 9.4 0.6 0.519 -9.481 -0.0092

7 14 -4 -3.46 -13.46 -0.0130

8 20.3 -10.3 -8.9095 -18.9095 -0.0183

9 18.9 -8.9 -7.6985 -17.6985 -0.0171

10 18.5 -8.5 -7.3525 -17.3525 -0.0168

11 19.7 -9.7 -8.3905 -18.3905 -0.0178

12 19.9 -9.9 -8.5635 -18.5635 -0.0180

13 16.5


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39

TABLE FOR LIFT, DRAG SIDE FORCE READINGS ON

SYMMETRICAL AIRFOIL

Model Angle of

Attack COS

Velocity Lift

Force

(FA) Kg

Drag

Force

Kg

Side

Force

Kg

A= S*C

S=0.295m

C=0.1m

FT

inKg

0 1 64.1 0.19 0.52 -0.02 0.02950 7.969

-5 0.996 64.1 -1.12 0.7 -0.01 0.02950 7.938

-10 0.984 64.1 -2.17 0.85 -0.01 0.02950 7.842

-15 0.965 64.1 -3.29 1.12 -0.04 0.02950 7.691-20 0.939 64.1 -3.1 1.91 -0.07 0.02950 7.483

5 0.996 64.1 2.38 0.52 -0.1 0.02950 7.938

10 0.984 64.1 4.1 0.56 -0.19 0.02950 7.842

15 0.965 64.1 4.76 0.62 -0.23 0.02950 7.691

SYMMETRICAL

AEROFOIL

20 0.939 64.1 2.99 1.69 -0.16 0.02950 7.483


SYMMETRICAL AIRFOIL

Model Angle of

Attack COS

Velocity Lift Force

(FA) Kg

Drag

Force Kg

Side Force

Kg

A= S*C

S=0.295m

C=0.1m

FT in Kg

0 1 40 0.03 0.12 -0.01 0.02950 3.103

-5 0.996 40 -0.6 0.28 -0.01 0.02950 3.091

-10 0.984 40 -0.81 0.32 -0.01 0.02950 3.054

-15 0.965 40 -1.25 0.5 -0.02 0.02950 2.995

-20 0.939 40 -1.18 0.71 -0.05 0.02950 2.914

5 0.996 40 0.79 0.16 -0.03 0.02950 3.09110 0.984 40 1.27 0.2 -0.06 0.02950 3.054

15 0.965 40 1.79 0.24 -0.07 0.02950 2.995

SYMMETRICAL

AEROFOIL

20 0.939 40 1.04 0.63 -0.09 0.02950 2.914

GRAPH OF LIFT, DRAG SIDE FORCE FOR SYMMETRICAL

AEROFOIL AT V= 64.1


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40

GRAPH OF LIFT, DRAG SIDE FORCE FOR SYMMETRICAL

AEROFOIL AT V= 40.0


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41


UNSYMMETRICAL AIRFOIL

Model

Angle

ofAttack

COS

Velocity

Lift

Force(FA)

Kg

DragForce

Kg

SideForce

Kg

A= S*CS=0.295m

C=0.1m

FT in

Kg

CL

0 1 64.1 3.02 0.5 -0.08 0.02950 7.969 0.379

-5 0.996 64.1 0.38 0.88 -0.08 0.02950 7.938 0.048

-10 0.984 64.1 -1.02 1.28 -0.07 0.02950 7.842 -0.13

-15 0.965 64.1 -1.32 1.63 -0.07 0.02950 7.691 -0.17

-20 0.939 64.1 -1.55 1.84 -0.09 0.02950 7.483 -0.20

5 0.996 64.1 3.87 0.56 -0.18 0.02950 7.938 0.488

10 0.984 64.1 4.28 0.58 -0.22 0.02950 7.842 0.54

UNSYMMETRICAL

AIRFOIL

15 0.965 64.1 5.02 0.6 -0.3 0.02950 7.691 0.653


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42

20 0.939 64.1 6.16 0.72 -0.39 0.02950 7.483 0.823


UNSYMMETRICAL AIRFOIL

Model

Angleof

Attack

COS

Velocity

LiftForce

(FA)

Kg

Drag

Force

Kg

Side

Force

Kg

A= S*C

S=0.295m

C=0.1m

FT inKg CL

0 1 40 1.23 0.22 -0.04 0.02950 3.103 0.39

-5 0.996 40 0.14 0.32 -0.03 0.02950 3.091 0.045

-10 0.984 40 -0.4 0.46 -0.02 0.02950 3.054 -0.13

-15 0.965 40 -0.49 0.55 -0.03 0.02950 2.995 -0.16

-20 0.939 40 -0.49 0.58 -0.04 0.02950 2.914 -0.16

5 0.996 40 1.56 0.21 -0.07 0.02950 3.091 0.505

10 0.984 40 1.71 0.22 -0.09 0.02950 3.054 0.56

15 0.965 40 1.98 0.24 -0.21 0.02950 2.995 0.661

UNSYMMETRICAL

AIRFOIL

20 0.939 40 2.33 0.28 -0.16 0.02950 2.914 0.80

GRAPH OF LIFT, DRAG SIDE FORCE FOR UNSYMMETRICAL

AEROFOIL AT V= 64.1


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43

GRAPH OF LIFT, DRAG SIDE FORCE FOR UNSYMMETRICAL

AEROFOIL AT V= 40.0


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44

TYPICAL DRAG STUDIES ON BLUFF BODIES AND

AUTOMOBILES

At Velocity V=64.1

ModelDrag

Force

Projected

dimension

in mm

Projected

AreaFt Cd

Circular disc 2.09 120 0.0113 3.05271 0.68464

Sphere 0.74 100 0.0078 2.10718 0.35118

Hemispherical

Bowl 2.05 100 0.0078 2.10718 0.97286

Car 1 0.52Car 2 0.91


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45

At Velocity V=40

ModelDrag

Force

Projected

dimensionin mm

Projected

Area Ft Cd

Circular disc 0.78 120 0.0113 1.18875 0.65615

Sphere 0.37 100 0.0078 0.82055 0.45092

Hemispherical

Bowl 0.74 100 0.0078 0.82055 0.90183

Car 1 0.19

Car 2 0.36

3 R

STATICPRE.

3ph.ACSUPPLY

OUTLET

TEST SECTION

DIFFUSEREFFUSERAIR INLET

HONEY COMBMESH SCREEN

PITOT TUBE

AXIAL FLOWFAN

ANY ONEAT A TIME

FLOW VISUALIZATION

STUDY(OPTIONAL)PRESSURE

DISTRIBUTION STUDY FORCE STUDY

- CYLINDER- FLAT DISC- AIRFOIL OR

- AUTOMOBILE VEHICLEMODEL OR

- OPTIONAL MODELS

SMOKEGEN.

SMOKEDISTRIBUTION

SMOKE

MULTI BANK MANOMETER

- AIRFOIL OR

- CYLINDER OR

- OPTIONALMODELS

- AIRFOIL

SYMMETRICALUN SYMMETRICAL

- AUTOMOBILE

VEHICAL MODEL

- BLUFF BODIES- OPTIONAL MODELS

3 FORCESTUNNEL BALANCE

AIR SUPPLY FROM BLOWER

FIG . 1 LOW SPEED WIND TUNNEL SCHEMATIC OF INSTRUMENTATION AND EXPERI


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46

FLOW VISUALIZATION USING WATER CHANNEL

AIM:

To visualize the flow using water flow channel by using twodimensional object.

APPARATUS REQUIRED:

Water flow channel, two dimensional surfaces model.

DESCRIPTION:

The water flow channel is a device which is used to visualize the two

dimensional flow over an object. The channel consist of a test section

proceeded by a contraction passage. The contraction passage increases the

test section speed; the corner vanes in the return circuit provide a smooth

entry of water into contraction. The entire setup is arranged in a shallow

rectangular tank filled with water to a required level. The flow in the test

section is established by means of two sets of rotating flow Blades wheel

in opposite directions. The water is re-circulated so that the system works

continuously. A HP DC motor through a belt pulley drive arrangementwhich drives the blade wheel at a lower speed. The speed of the stream is

kept low to avoid turbulence and ripple formation on the water surface.

PROCEDURE:

Two-dimensional models are kept in test section and the flow pattern

around these models is made visible by placing silver threads. The water

channel is well suited for the study of real flow visualization is used to

study the effects of the shape of the model on the flow pattern, when kept

in a stream line flow. The following models are used for flow

visualization.

a) Square and triangle

b)Airfoil.

1. Laminar flow of water in a channel is in flow condition.


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2. For above condition operate the variable drive in clockwise direction.

3. Observe the condition of flow should be laminar.

4. In the middle flow path keep the model (Aerofoil, Square, and

Triangle) one at a time.5. The silver threads are placed (called as aluminum powder) in the path

of water flow and model. The silver threads travels in the direction of

flow and passes through the model closely observe the pattern formed

around the model. It can be photographed.

6. The equipment is made of stainless steel tray in which contractpartitions are made for flow path.

7. The flow path length 6.

8. Width of the channel is two side ways 6.

9. Width of the channel in centre 9.

10. Curved blade at entry and on the other end is made for smooth flow.

11. The curved blades can be removable type on the other end for differentconditions.

12. A common shaft is connected to the turbine wheel blades.

13. The shaft is connected by belt to DC variable motor.14. The RPM of the motor can be red in digital meter.

15. Once the experiment is completed drain the water.

16. The water height in the channel should not be more than 2 in heightfrom base floor.


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