AERODYNAMICS-Lab-Manual.docx

8/10/2019 AERODYNAMICS-Lab-Manual.docx

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SRINIVASAN ENGINEERING COLLEGE

(Approved by AICTE, New Delhi and affiliated to Anna University, Chennai)

An ISO 9001:2008 Certified Institution

PERAMBALUR 621212

DEPARTMENT OF AERONAUTICAL ENGINEERING

AE2258

AERODYNAMICS laboratory

MANUAL


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LIST OF EQUIPMENTS(for a batch of 30 students)

SI.NO REQUIRMENT QUANTITY

1Blower, Balance, and small aspect ratio

model1 each

2 Water flow channel & models 1 set

3 Subsonic wind tunnel 1 No.

4 Smoke apparatus and rake

1 each

5 Manometer, Pitot-Static tube 1 No.

6

Circular cylinder and Aerofoil pressure

distribution models 1 each

7 Wind tunnel strain gauge balance 1 No.

8Supersonic wind tunnel, Mercury

manometer1 No.

9 Schlieren system and Shadow graph system 1 No.

10 Sharp nosed and Blunt nosed models 1 No.


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UNIVERSITY PRACTICAL EXAMINATION

ALLOTMENT OF MARKS

Internal Assessment = 20 marks

Practical Examination = 80 marks

INTERNAL ASSESSMENT[20 Marks]

Staff should maintain the assessment Register and the Head of the Department should monitorit.

SPLIT UP OF INTERNAL MARKS

Record Note 10 marks

Model Exam 5 marks

Attendance 5 marks

Total 20 marks

UNIVERSITY EXAMINATION

The examination will be conducted for 100 marks. Then the marks will be calculated to 80 marks.

ALLOCATION OF MARKS

Aim and Procedure 30 marks

Modeling 30 marks

Simulation 20 marks

Result 10 marks

Viva Voce 10 marks

Total 100 marks


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LIST OF EXPERIMENTS AS PER SYLLABUS

Generation of lift and tip vortices.

Flow visualization in water flow channel

Flow visualization in smoke tunnel

Plot of RPM Vs. test section velocity in a subsonic wind tunnel.

Pressure distribution over circular cylinder.

Pressure distribution over airfoil and estimation of CL and CD.

Force measurement using wind tunnel balance.

Mach number distribution in nozzle of supersonic wind tunnel.

Use of Schlieren system to visualize shock.

Use of Shadow graph system to visualize shock.

Total: 45 PERIODS


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TABLE OF CONTENTS

EXCERSISE NO. TITLE PAGE NO.

LIST OF NOMENCLATURES

1Generation of Lift and Tip vortices

2Flow visualization in smoke tunnel

3Flow visualization in smoke tunnel

4Plot of RPM vs. Test section velocity in a subsonic wind tunnel

5Pressure distribution over circular cylinder

6Pressure distribution over Symmetrical Airfoil and estimation ofCP

7Pressure distribution over Asymmetrical Airfoil and estimationof CP

8Force measurement over Asymmetrical Airfoil

using wind tunnel balance

9 Use of Schlieren system to visualize shock

10 Use of Shadow graph system to visualize shock


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LIST OF NOMENCLATURES

SI.NO. SYMBOL DESCRIPTION

1 Cp Pressure coefficient

2V Free stream velocity of the fluid

3PT Total pressure

4PS Static pressure

5 q Dynamic pressure

6 air Free stream fluid density (Air at sea level and 15 C) is 1.225 kg / m3

7 water Water density is 1000 kg / m3

8 g Acceleration due to gravity is 9.81 m / s2

9 CL Coefficient of lift force

10 CD Coefficient of drag force

11 CS Coefficient of side force

12 FT Theoretical force

13 FL Lift force

14 FD Drag force

15 FS Side force

16 S Surface Area (S ) = Span (b) Chord (C)

17 Angle of attack


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Ex. No.: 01 GENERATION OF LIFT AND TIP VORTICES

Date:

Aim:

To understand the concept in generation of lift and to know about tip vortices

Apparatus Required:

Subsonic Wind Tunnel

Smoke Generator

Airfoil Models

Procedure:

Switch ON the Main which is connected to the 440 V, 32 A, 3 ph, AC powersupply with neutraland earth connection.

Check all the switches of the controller are in OFF position before starting.

Switch ON the MCB (Miniature Circuit Breaker) of Console Board.

Put-on the mains and observe the main indicator lights are glowing at the bottom ofthe control

panel.

Fix the smoke distributor at the starting portion of the test section.

Fix a symmetrical or an asymmetrical airfoil model in the test section, at requiredorientation.

Switch ON the Heater which is connected to the 2 ph, AC power supply.

Wait 5 minutes, till the heater gains some heat energy.

Let the blended fuel (25 % of Kerosene and 75 % of Diesel) to flow over the heater by open the

fuel flow control valve slightly.

Switch ON theblower and light in the console board.

Ensure the out-coming of smoke and connect the hose to the smoke distributor.

Now observe the smoke being forced out of the smoke distributor at the entry of the test section.


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Figure 1. FLOW OVER AN AIRFOIL

Control the main flow of air in the test section by controlling the AC motor speed, so that the

smoke flow pattern to persist across the model. Keep the speed at very low; higher velocities

will defuse the smoke.

Observe the flow pattern over the model.

Never switch ON the heater for long time with or without the fuel being supplied to the unit.

After the experiment, close the fuel flow control valve, switch OFF the heater and light, and run

the blower for some time. This is just to exhaust out any smoke left in the smoke generator unit.

Then switch OFF all accessories.

Result:

Thus the generation of lift and formation of tip vortices has been understood.


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Viva questions:

How the lift is generates?

What is a vortex?

How the drag is generates?

Explain Bernoullis principle?

What are the aerodynamic forces?


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Ex. No.: 02 FLOW VISUALIZATION IN SMOKE TUNNEL

Date:

Aim:

To understand the formation of layers over the models due to air flow and to visualize the

flow separation.

Apparatus Required:


Smoke Generator

Models

Procedure:

Switch ON the Main which is connected to the 440 V, 32 A, 3 ph, AC power supply with

neutral and earth connection.



Put-on the mains and observe the main indicator lights are glowing at the bottom of the control

panel.

Fix the smoke distributor at the starting portion of the test section.

Fix a model in the test section, at required orientation.

Switch ON the Heater which is connected to the 2 ph, AC power supply.

Wait 5 minutes, till the heater gains some heat energy.

Let the blended fuel (25 % of Kerosene and 75 % of Diesel) to flow over the heater by open the

fuel flow control valve slightly.

Switch ON the blower and light in the console board.

Ensure the out-coming of smoke and connect the hose to the smoke distributor. Now observe the

smoke being forced out of the smoke distributor at the entry of the test section.

Control the main flow of air in the test section by controlling the AC motor speed, so that the

smoke flow pattern to persist across the model. Keep the speed at very low; higher velocities will

defuse the smoke.


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Observe the flow pattern over the model.

Never switch ON the heater for long time with or without the fuel being supplied to the unit.

Figure 2. Flow visualization over an airfoil in smoke tunnel

After the experiment, close the fuel flow control valve, switch OFF the heater and light, and run

the blower for some time. This is just to exhaust out any smoke left in the smoke generator unit.

Then switch OFF all accessories.


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Result:

Thus the formation of layers over the models due to air flow and the flow separation has

been visualized.

Viva questions:

What is flow visualization?

What are the types of flow visualization?

What is a smoke tunnel?

How do you estimate the drag?

What is aerodynamic centre?


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Ex.No : 03 FLOW VISUALIZATION IN WATER FLOW CHANNEL

Date:

AIM:

To visualize the flow over the 2D objects using water flow channel

APPARATUS REQUIRED:

Water flow channel

Models

Circular Cylinder

Triangle

Square Cylinder

Aerofoil

DESCRIPTION:

The device used to visualize the 2D flow part on object.

The channel consists of a test shown speed, processed by contraction.

The contraction increases the test section speed & reduces the flow section lined and

unidirectional. The corner values in the return circuit provides a smooth entry of water into the

contraction.

The entire setup is arranged in a hollow rectangular box like tank filled with water to a required

height.

The flow in the test section is established by means of two sets of parallel discs rotating in opposite

direction which is immersed in water .

The water is recirculated so that the system can work continuously which is powered by a half

HPDC motor through a bell pulley device arrangement which drives at a lower speed.

The speed of the stream is kept low so as to avoid turbulence formulation on the water surface


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PRODUCER:

Place the circular cylinder in the test section

The flow patterns around the models are made visible by sprinkling the aluminum powder.

Now change the model & repeat the procedure.

This is used to study the effect of the model shape on the flow pattern when kept in the

streamlined flow.

Result:

Thus the formation of layers over the models due to water flow and the flow separation

has been visualized.

Viva questions:

What is flow visualization?

What are the types of flow visualization?

What is a water flow channel?

What are the types of models used?


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Ex.No : 04 PLOT OF RPM VS. TEST SECTION VELOCITY IN A SUBSONIC

WIND TUNNEL

Date:

Aim:

To understand the variation in air velocity at the mid of the test section according to speed

Apparatus Required:


Static-Pitot tube

Procedure:






panel.

Set the Pitot tube at mid position of the test section.

Control the main flow of air in the test section by increasing the AC motor speed gradually.

Note the velocity (m/s) for different speed of the drive (RPM).

After the experiment switch OFF all accessories.

The given Subsonic Wind Tunnel is equipped with a drive control which shows the speed in

Frequency (Hz).

To convert the Frequency into RPM,

RPM=120*frequency/ No. of poles

This driven having 4 poles, can find the RPM for diverse of Frequency.

Plot a graph for RPM vs. Test section velocity by taking x-axis for velocity and y-axis for RPM.


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Tabulation:

Velocity at mid of test section for different Frequency

Sl. No.Frequency

(Hz)RPM

Velocity

(m/s)1 5 150

2 10 300

3 15 450

4 20 600

5 25 750

6 30 900

7 35 1050

8 40 1200

9 45 1350

10 50 1500

Graph:

Plot for RPM vs. Test section Velocity

Result:

Thus the plot for RPM vs. Test section Velocity has been drawn.


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Viva questions:

What is wind tunnel?

What are the types of wind tunnel?

What is a smoke tunnel?

How do you calibrate the wind tunnel?

What is centre of pressure?


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Ex. No. : 05 PRESSURE DISTRIBUTION OVER CIRCULAR CYLINDER

Date :

Aim:

To find the Coefficient of pressure over circular cylinder

Apparatus Required:


Circular Cylinder with Pressure taps

Procedure:






panel.

Fix the circular cylinder in the test section, at required orientation.

Connect the pressure taps of manometer to the respective taps of model.


Set the speed as constant and note the velocity from the RPM vs.Test section Velocity

plot.

Measure and note the readings from the manometer.


Find the coefficient of pressure at each point from calculation.

Plot a graph for Cylinder Surface Pressure vs. Pressure Tapping Points by taking x-axis for

Pressure Tapping Points and y-axis for Cylinder Surface Pressure.


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Tabulation:

Values of pressure Coefficient over circular cylinder

Air at velocity = ________ m/s for frequency = ________ Hz

Location Refer.Pressure,Pr (cm)

CylinderSurface

Pressure,P(i) (cm)

Pressures PT -PS(cm)

Cp=(PT-

PS v2

Pm = (

Pr-P(i) )

(cm)

PT=Pm(cm)

PS = ( Pr

P13 )

(cm)

1

2

3

4

5

6

7

8

9

10

11

12

13

Graph:

Plot for Cylinder Surface Pressure vs.Pressure Tapping Points

Result:

Thus the pressure Coefficient over the circular cylinder has been found and required plot has been

drawn.


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Viva questions:

What is pressure coefficient?

When will the cylinder produce lift?

What is a stagnation point?

What is static pressure?

What is centre of pressure?


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Ex. No.: 06 PRESSURE DISTRIBUTION OVER SYMMETRICAL AIRFOIL AND

ESTIMATION OF Cp

Date:

Aim:

To find the Coefficient of pressure over Symmetrical Airfoil

Apparatus Required:


Symmetrical Airfoil model with Pressure taps

Formulae Used:

1. Total Pressure = Static Pressure + Dynamic Pressure

2. For manometer readings,


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Procedure:






panel.

Fix the Asymmetrical Airfoil model in the test section, at required orientation.

Connect the pressure taps of manometer to the respective taps of model.


Set the speed as constant and note the velocity from the RPM vs. Test section Velocity

plot.

Measure and note the readings from the manometer for different Angle of Attacks.


Find the coefficient of pressure at each point from calculation.

Plot a graph for Asymmetrical Airfoil Surface Pressure vs. Pressure Tapping Points by taking x-

axis for Pressure Tapping Points and y-axis for Asymmetrical Airfoil Surface Pressure at certain

Angle of Attack.


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Tabulation:

Values of pressure coefficient over Symmetrical Airfoil

Air at velocity = ______ m/s for frequency = ________ Hz

Graph:

Plot for Symmetrical Airfoil Surface Pressure vs. Pressure Tapping Points

Result:

Thus the pressure Coefficient over the Asymmetrical Airfoil model has been found and required plot has

been drawn.


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Viva questions:


When will the cylinder produce lift? What is centre of pressure?

What is an airfoil?

What are the types of airfoil?

What is an asymmetrical airfoil?


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Ex. No.: 07 FORCE MEASUREMENT OVER SYMMETRICAL AIRFOIL USING

WIND TUNNEL BALANCE

Date :

Aim:

To find the Coefficient of forces over Symmetrical Airfoil

Apparatus Required:


Symmetrical Airfoil model with Balance

Formulae Used:

Procedure:




Switch ON the MCB (MiniatureCircuit Breaker) of Console Board.


panel.

Fix the Symmetrical Airfoil model in the test section, at required orientation.



plot.

Measure and note the readings from the force indicators for different Angle of Attacks.


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Find the coefficient of forces for considered Angle of Attack from calculation.

Plot a graph for Coefficient of forces vs. Angle of Attack by taking x-axis for Angle of Attack and

y-axis for coefficient of forces.

Tabulation:

Graph:

Plot for Coefficient of forces vs.Angle of Attack

Result:

Thus the Coefficient of Forces over the Symmetrical Airfoil model has been found and required plot has

been drawn.


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Viva questions:


How the cylinders produce drag?

What is camber?

What is an airfoil?


What is symmetrical airfoil?


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Ex. No.: 08 FORCE MEASUREMENT OVER ASYMMETRICAL AIRFOIL USING

WIND TUNNEL BALANCE

Date :

Aim:

To find the Coefficient of forces over Asymmetrical Airfoil

Apparatus Required:


Asymmetrical Airfoil model with Balance

Formulae Used:

Procedure:




Switch ON the MCB (MiniatureCircuit Breaker) of Console Board.


panel.

Fix the Asymmetrical Airfoil model in the test section, at required orientation.



plot.


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Measure and note the readings from the force indicators for different Angle of Attacks.


Find the coefficient of forces for considered Angle of Attack from calculation.

Plot a graph for Coefficient of forces vs. Angle of Attack by taking x-axis for Angle of Attack and

y-axis for coefficient of forces.

Tabulation:

Graph:

Plot for Coefficient of forces vs.Angle of Attack

Result:

Thus the Coefficient of Forces over the Asymmetrical Airfoil model has been found and required plot has

been drawn.


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Viva questions:

What is wind tunnel balance?

How the cylinders produce drag?

What is chord?

What is an airfoil?


What is asymmetrical airfoil?


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Ex. No.: 09 USE OF SCHLIEREN SYSTEM TO VISUALIZE SHOCK

Date :

Aim:

To study the use of Schlieren system to visualize shock

Apparatus Required:

Supersonic Wind Tunnel

Schlieren system

Introduction:

Schlieren method visualizes the distribution of fluid density within a fluid, as fluid density

controls the index of refraction. Regions of density gradient deflect light beams, shifting their position on

the image plane. The relative change in light intensity can be used to infer the original density and flow

field.

Optical Principle:

There are several methods commonly used to visualize refractive index or density changes in

liquids, gases, liquids and solids. Generically these include shadowgraphs, schlieren and interferometric

techniques. These systems are used to visualize temperature gradients, shock waves in wind tunnels,

nonhomogeneous areas in sheet glass, convection patterns in liquids, etc.

Shadowgraph systems are often used where the density gradients are large. This technique also

can accommodate large subjects, is relatively simple in terms of materials required and in terms of cost is

probably the least expensive technique to set-up and operate.

Interferometric techniques are usually highly sensitive, complex in set-up, can provide

quantitative information but are expensive systems and can only deal with relatively small subjects.

Schlieren systems are intermediate in terms of sensitivity, system complexity and cost. Schlieren

systems can be configured to suit many different applications and sensitivity requirements. Typically,

however, they are still considered too complex and expensive to implement in many cases where a simple

density visualization system is needed.


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While discussed and introduced in the early '50's, the focusing schlieren method is one that uses

no unusual or expensive optical elements and yet achieves high sensitivity at relatively low cost. Plus it

relies on low-tech system "ingredients". As you can see by the attached illustration showing two students

setting up a demo system, it is perfect for use in teaching situations where cost tends to be a primary

concern.

Unlike other systems, the focusing schlieren technique uses a broad light source instead of a small

or point light source. This source is usually made up of a regular array of black and white elements. To

make one requires simply a large translucent, opalescent, sheet of plastic onto which opaque stripes are

fastened creating a black line/bright line effect. This screen is illuminated from behind with a single flood

lamp or a flash, or a bank of them.

If this screen is located closer to the "imaging" lens than infinity, then the image of this screen is

reproduced at a distance somewhat larger than 1 focal length of the lens. If one makes a high contrast

negative photograph of the image of the screen, then the bright areas of the subject will reproduce as dark,

opaque, lines at the location of the image of the screen and the black lines will reproduce as clear lines.

Then, if a subject of some kind is placed between the source and the camera lens, the image of

this subject will be reproduced sharply at a distance larger then that at which a sharp image of the screen

is reproduced. This essentially means that image points of this closer subject are made up, at the focus of

the image of this closer subject, by light rays that come to the camera lens from a large number of source

locations. Before these light rays become part of the sharply focused image of the subject they are part of

the sharply focused image of the source.

Now if the negative reproduction of the light source or screen is placed in the position where it

was when its photograph was made, then at any position farther away from the camera lens no light will

be seen because all the light from the clear areas of the source would be stopped by the dark lines of the

reproduction of the source.

If during the "steady state" condition of the systems the interfering physical reproductions of the

gridlines of the source are displaced slightly from the pint where they cause a total extinction of light,

then a grayish field of uniform brightness will be perceived. This field will become brighter until the

physical lines completely cover the dark lines of the image of the source grid allowing all the light present

in the clear, bright, areas of the source grid to pass.


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If the system is adjusted so that the obstruction and the image of the source grid are slighly

misaligned and a uniform, grey field is seen, then local variations in refractive index that cause the light

beam to move will become visible as local areas in the image plane that are brighter or darker than the

middle grey selected that indicates the "steady state" condition. Thus local variations in density can be

visualized. They can be recorded with simple auxiliary photographic equipment.

Figure 9. Operating principle of schlieren system

Light rays are bent whenever they encounter changes in density of a fluid. Schlieren systems are

used to visualize the flow away from the surface of an object. The schlieren system shown in this figure

uses two concave mirrors on either side of the test section of the wind tunnel. A mercury vapor lamp or a

spark gap system is used as a bright source of light. The light is passed through a slit which is placed such

that the reflected light from the mirror forms parallel rays that pass through the test section. On the other

side of the tunnel, the parallel rays are collected by another mirror and focused to a point at the knife

edge. The rays continue on to a recording device like a video camera.

Now if the parallel rays of light encounter a density gradient in the test section, the light is bent,or refracted. In our schematic, ashock wave has been generated by a model placed in the supersonic flow

through the tunnel test section. Shock waves are thin regions of high gradients in pressure, temperature

and density. A ray of light passing through the shock wave is bent as shown by the dashed line in the

figure. This ray of light does not pass through the focal point, but is stopped by the knife edge. The

resulting image recorded by the camera has darkened lines that occur where the density gradients are
http://www.grc.nasa.gov/WWW/k-12/airplane/oblique.htmlhttp://www.grc.nasa.gov/WWW/k-12/airplane/oblique.html


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present. The model completely blocks the passing of the light rays, so we see a black image of the model.

But more important, the shock waves generated by the model are now seen as darkened lines on the

image. We have a way to visualize shock waves.

The earliest schlieren photographs of shock waves were black and white images. The imageshown here is a color schlieren image produced by putting a prism near the slit and breaking the white

light into different colors. Notice that the resulting image is two dimensional while, in reality, shock

waves are three dimensional. So the schlieren photograph provides some valuable information about the

location and strength of the shock waves, but it requires some experience to properly interpret the results

of the process.

Procedure:

It is desirable to use a large aperture, relatively long focal length lens for the imaging lens. Some

surplus copier lenses can be applied for this purpose. The source grid should be placed at a

distance equal to four focal lengths of the lens. The subject field will be located at two focal

lengths from the lens. Therefore the lens will be making a life sized reproduction of the subject.

Due to this choice of distances, the lens will make an image of the source grid at a distance of 16

inches from the lens. This can be determined from the basic relationship that the reciprocal of the

lens' focal length is equal to the reciprocal of the object distance plus the reciprocal of the image

distance.

To make a reproduction of the source grid a piece of high contrast film material (possibly

stiffened by a piece of glass or held in or taped to a frame) is placed where the source grid comes

to a sharp focus. It goes without saying that this must be done in such a manner that only light

from the source grid falls on the photosensitive emulsion. This can be accomplished by baffling

or building a light tight box around the lens to film area.

It is important to note that the reproduction of the source grid will reflect any refractive index

inhomogeneities present due to the inclusion of imperfect windows in the system and this feature

alone often results in major cost benefits in terms of system setup since relatively low quality

optical components can be used between the one lens in the system and source.

After the film is exposed and developed, it is replaced in its original position. This can be

checked by visually examining the registration between the image of the source grid and its

physical negative reproduction as well as tracking the appearance of the subject field on a ground

glass placed, as mentioned above, at two focal lengths from the lens. It should be noted that slight


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misregistration between the two grids allows the operator to vary the brightness of the subject

field on the ground glass.

Once this relationship has been established, placing a density gradient two focal lengths from the

camera lens will cause this gradient to be visible on the ground glass. If the source of the

gradients is a hot soldering iron, for example, the warm air rising from the iron should be clearly

visible as rising plumes of light and dark from the iron itself.

Figure 9.1 Shock captured by schlieren system

A camera can be aimed at the ground glass and images of the disturbances created by the rising

density gradients can then ultimately be photographed. Conversely, if the whole system (from the

lens back to the ground glass) is built in a light tight container and the lens is equipped with

shutter, then film can be the ultimate image and exposures are made by simply operating the

shutter or firing a flash that illuminates the source grid for a brief instant. This is a focusing

schlieren photograph made directly onto film showing warm air rising from hot soldering irons.

Result:

Thus the use of schlieren system to visualize the shock is studied.

Viva questions: What is wind tunnel balance?

How the shock induces?

What are the types of shock?

What are flow visualization techniques?

Explain schlieren operating technique?
http://people.rit.edu/andpph/text-figures/schlieren-focus-3.jpg


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Ex. No.: 10 USE OF SHADOWGRAPH SYSTEM TO VISUALIZE SHOCK

Date:

Aim:

To study the use of Shadowgraph system to visualize shock

Apparatus Required:

Supersonic Wind Tunnel

Shadowgraph system

Introduction:

The density of a fluid varies with temperature, salinity, and pressure. And, the index of refraction

changes with fluid density. Variations in the refractive index deflect or phase shift light passing through

the fluid. If a screen is placed opposite the light source, these effects create shadows one the screen

creating an image called a Shadowgraph.

Operating principle:

The shadowgraph is the simplest form of optical system suitable for observing a flow exhibiting

variations of the fluid density. In principle, the system does not need any optical component except a light

source and a recording plane onto which to project the shadow of the varying density field. A shadow

effect is generated because a light ray is refractively deflected so that the position on the recording plane

where the undeflected ray would arrive now remains dark. At the same time the position where the

deflected ray arrives appears brighter than the undisturbed environment. A visible pattern of variations of

the illumination (contrast) is thereby produced in the recording plane. From an analysis of the optics of

the shadow effect it follows that the visible signal depends on the second derivative of the refractive index

of the fluid. Therefore, the shadowgraph as an optical diagnostic technique is sensitive to changes of the

second derivative of the fluid density.


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Figure 10. Operating principle of shadowgraph

Procedure:

It is evident that the shadowgraph is not a method suitable for quantitative measurement of the

fluid density. Owing to its simplicity, however, the shadowgraph is a convenient method of

obtaining a quick survey of a flow in which the density changes in the described way.

This applies particularly to compressible gas flows with shock waves that can be considered as

alterations of the gas density with an extremely intense change in curvature of the density profile,

i.e., a change of the respective second derivative.

The observation of shock waves in gases by means of shadowgraphy goes back to the 19th

century when these flow phenomena were discovered by means of this optical technique.

Figure 10.1 Shadowgraph setup


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Due to the very simple optical setup, the shadow effect resulting from inhomogeneous density

fields can be observed also outside a laboratory, with the sun serving as the light source, e.g., the

sun light may project onto a solid wall shadow patterns that are caused by fuel vapor rising in the

air.

The camera that records a down-scaled picture is focused onto a plane at distance lfrom the test

field. This plane corresponds to the position of the recording plane.

The intensity of the shadow effect, or the sensitivity of the shadowgraph, increases with the

distance l. On the other hand, the flow picture is the more out of focus the greater l, so that a

compromise between optical sensitivity and image quality has to be found. The optical sensitivity

of the shadowgraph is, in principle, an order of magnitude lower than that of schlieren or

interferometric techniques.

Figure 10.2 Shock captured by shadowgraph system

Result:

Thus the use of shadowgraph system to visualize the shock is studied.

Viva questions:

Explain schlieren operating technique?

How the shock induces?

What are the types of shock?

What type of flow visualization techniques is more accurate?


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UNIVERSITY QUESTIONS

How the lift is generates? How the vortices generates?

Explain the inducement of lift and drag?

Visualize the flow using water channel.

Visualize the flow using smoke tunnel.

Calibrate the subsonic wind tunnel using RPM method.

Calibrate the subsonic wind tunnel using test section velocity method.

Determine the pressure distribution over a circular cylinder.

Determine the pressure distribution over symmetrical aerofoil.

Determine the pressure distribution over a symmetrical aerofoil. Also find the CPand CD.

Determine the pressure distribution over asymmetrical aerofoil

Determine the pressure distribution over a symmetrical aerofoil. Also find the CPand CD.

Determine the force over the symmetrical aerofoil using wind tunnel balance technique.

Determine the force over the asymmetrical aerofoil using wind tunnel balance technique.

Explain Schlieren photography method.

How the shock is captured in Schlieren photography method.

Explain Shadow graphy method.

How the shock is visualized in shadow graphy method.

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