RAJALAKSHMI ENGINEERING COLEGE, CHENNAI B.E. AERONAUTICAL ENGINEERING SEMESTER-IV AE 2258 AERODYNAMICS LABORATORY REGULATION 2008 OBJECTIVE:
To familiarize students in basic aerodynamics and the use of wind tunnels.
LIST OF EXPERIMENTS
1. Introduction –low speed wind tunnel 2. Flow visualization in water flow channel 3. Flow visualization using smoke generator 4. Plot of RPM Vs test section velocity in a subsonic wind tunnel. 5. Study of lift characteristics on symmetric aerofoil, cambered aerofoil and bluff bodies 6. Pressure distribution over rough and smooth circular cylinder 7. Pressure distribution over symmetric and cambered airfoil and estimation of CL and CD. 8. Study of Calibration of Supersonic wind tunnel. 9. Velocity distribution in nozzle using supersonic free jet 10. Flow visualization using Shadowgraph system
AUGMENTED EXPERIMENT
1. Pressure distribution over wedge airfoil and estimation of CL and CD 2. Mini Project
EXP.NO: - 1 LOW SPEED WIND TUNNEL Aim To study in details about the low speed 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 scale models and sometimes actual structures in wind tunnel. The size, speed and other environmental conditions of the tunnel are determined by the actual under problems. Leaving the size and environmental conditions to the actual users, the speed determines the type of the tunnel namely subsonic (low speed), near sonic, transonic, supersonic and hypersonic. While the speed of these tunnels is obviously named with the reference to the sonic (sound) velocity, the low speed tunnel which is our concern is below 300mph. an alternative definition to the low speed tunnel would be the tunnel where the compressibility of air is negligible.
Specifications:
Type of tunnel Test section Air speed Contraction ratio Overall size Power required Drive
: : : : : : :
Subsonic Suction Type 300mm 300mm 500mm (Length) Upto 50m/s 9:1 1.2m 2.2m 7.0m AC 3 phase, 440 volts, 14A Axial flow fan driven variable speed DC Motor with Thyristor Controller
Main parts:
Honey comb inlet mesh screen, effuser, diffuser, blower unit with DC motor, lift/drag balance, multitube manometer, smoke generator, pitot tube and transverse mechanism, digital lift/drag indicators. Preparation:
Tunnel balance is a two-component type designed using electrical strain gauge to indicate lift and drag forces on digital lift and drag indicator in kg and Newton. Balance is intended to indicate lift and drag incase of aerofoils and drag force in case of bluff bodies. Example: spherical, hemispherical, round disc and automobile models. These models are put on the string. Before the model is put on the string air is blown and it is necessary to calibrate balance along with digital meters. For the purpose, a calibration jig is provided with a set of weights.
Fix calibration jigs and to the top of the test section with the help of wing nuts. Fix dummy rod to string and see that the top dummy rod is at the centre of test section. Now pass the wire around the dummy rod and hang it to the weights. Switch on the strain indicator and observe the reading on it be zero. If reading are not same after weights are added use CAL knob to obtain the correct reading. Remove the calibration jig dummy rod and fix the model and run the tunnel for studying various types of experiments. Operating instructions:
All the components mentioned are integrated for conducting various experiments. Follow the instructions given below. 1. Connect the power card to the 400v,30A,3PH AC power supply with neutral and earth connections. 2. Keep the speed controller knob at 0 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 control and observe the console light is ON 6. Select particular experiment and fix the requirement model in the test section 7. Follow the instruction for “preparation and 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 knobs slowly in the clockwise direction and observe vthe DC motor picking up the speed gradually. 10. Observe the movement of manometer liquid in inclined manometer(velocity indicator). Set the requirement valve of air velocity by adjusting the knob on DC drive. 11. Take readings in the respective experiments detailed. 12. While stopping, gradually decrease the speed and then switch of the DC motor controller.
Note:
1. Do not clean the transparent test section windows with petrol, kerosene or other chemical detergents. Use only the light soap water. 2. Check the electrical installation property before switching it ON. 3. Do not bring any fire near the smoke generator during the flow visualization experiment.
EXP NO: - 2FLOW VISUALIZATION IN WATER FLOW CHANNEL Aim:-
To visualize the flow over two dimensional objects using water flow channel. Apparatus required:
Water flow channel, various shapes (cylinder, airfoil and square). Description: The water flow channel is a device used to visualize the 2D flow past an object. The channel consists of a test section proceeded by contraction. This contraction increases the test section speed and renders the flow stream lined and uni-directional. The corner valves in the return circuit provide a smooth entry of water into the contraction. The entire set up is arranged in a shallow rectangular box like tank filled with water to a required height. The flow in the test section established by means of two sets of parallel discs rotating in opposite direction which is immersed in water. The water is re-circulated so that the system can work continuously. A half HP AC motor through a belt pulley drives arrangement, which drives at a lower speed. The speed of the stream is kept low so as to avoid turbulence and ripple formation on the water surface. Procedure:
Two-dimensional models are kept in the test section and the flow pattern around these models is made visible by sprinkling aluminum powder. The water channel is well situated for the study of real flow around two dimensional objects. This type of flow visualization technique is used to study the effect of the shape model on the flow pattern when kept in a streamlined flow. The following models are used for flow visualization. a) Circular cylinder b) Square prism c) Symmetric aerofoil
Result:
Thus, the flow over the two dimensional objects has been visualized using the water flow channel.
EXP NO:-3 FLOW VISUALIZATION USING SMOKE GENERATOR
Aim:To study the flow visualization technique by smoke generation. Apparatus required:-
Subsonic wind tunnel, Smoke generator, Liquid paraffin, Any Aerodynamic model Procedure:-
1. Check all the connections of the tubes. 2. Pour liquid into the reservoir, so that half of it is filled. 3. Then raise the wire of the reservoir such that the liquid level in the water tank of the smoke generator is above some mm below the nozzle of the outlet. 4. Connect the heater with the heater control which is a 400W controller. 5. Keep the controller in the minimum and switch on the power to the heater using the function knob. 6. Slowly increase the heating up to 3/4th of the capacity. 7. Observe the liquid paraffin which will start flowing wider. 8. The liquid level rises in the tube with the bubbles of liquid paraffin start reaching the nozzle exit. 9. At this point of time turn on the blower to send the pressurized air. The cold air mix with oil and forms dense smoke. 10. By controlling the heating and the liquid level in the tube, a good dense white smoke can be generated.
Result:-
Thus, the flow visualization technique is studied by generating smoke.
EXP NO:-4 PLOT OF RPM VS TEST SECTION VELOCITY VELOCITY IN A SUBSONIC SUBSONIC WIND TUNNEL
Aim To estimate the test section speed characteristics of the subsonic wind tunnel with respect to the rpm of the drive motor. Apparatus Required
Subsonic Wind tunnel, Pitot tube Procedure:
All the components mentioned are integrated for conducting various experiments. Follow the instructions given below. 1. Connect the power card to the 400v, 30A, 3PH AC power supply with neutral and earth connections. 2. Keep the speed controller knob at 0. 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 control co ntrol and observe the console light is ON. 6. Select particular experiment and fix the requirement model in the test section. 7. Follow the instruction for “preparation and 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 knobs slowly in the meter and observe the AC motor picking up the speed gradually. 10. Observe the movement of methanol liquid in inclined manometer (velocity indicator). 11. Take readings in the respective experiments detailed. 12. While stopping, gradually decrease the speed and then switch of the AC motor controller.
Tabulation:
S.NO.
RPM
V = 3.62√h m/s
1
200
7.1
2
400
15.1
3
600
23.6
4
800
30.8
5
1000
38.8
Graph:
A graph between rpm and velocity has to be plotted.
RPM Vs Velocity 45 40 35 30 25 20
RPM Vs Velocity
15 10 5 0 0
200
400
600
800
1000
1200
RPM
Result:-
Hence the test section speed characteristics of the subsonic wind tunnel with respect to the rpm are estimated and it shows that there is a linear variation of velocity with respect to the variation of RPM.
EXP NO: - 5 STUDY OF LIFT& DRAG CHARACTERISTICS OF SYMMETRIC, CAMBERED AEROFOIL AND BLUFF BODIES Aim:
To study the lift/drag characteristics on symmetrical aerofoil, cambered aerofoil and bluff bodies Apparatus required:
1) 2) 3) 4)
Low speed wind tunnel Symmetric aerofoil model Cambered aerofoil Bluff body
Formula Used:
Lift Coefficient
C L
L
1 2
Drag Coefficient
C D
2
V S
D
1 2
2
V S
L = Lift in N D = Drag in N 3 = Density of air in kg/m 3 V = Velocity in m /s 2 S = Wetted area in m
Procedure:
a) Prepare a wind tunnel and calibrate it with the lift drag balance and ensure it is fully serviceable. b) The operating instructions are to be meticulously followed. c) Fix the model on the vertical v ertical string and lock it. d) Close the test section and ensure that no items are left inside the test section before closing. e) Blank all the points. f) Set the lift force indicator to zero. g) Fix the required air velocity using the velocity indicator.
h) Now by changing the angle of attack the corresponding lift force is noted down. i) The same is repeated for different angle of attacks.
TABULAR COLUMN
Sl.No.
Angle of attack (α)
L
D
CL
CD
Graph: aerofoil (symmetric and cambered)
1) Coefficients of lift Vs angle of attack. 2) Coefficient of drag Vs angle of attack. 3) CD Vs CL. 0.8 0.6 0.4 0.2 CL
0
‐30
‐20
‐10 ‐0.2 0 ‐0.4 ‐0.6 ‐0.8 ‐1
10
20
30
CD
Graph: (bluff body)
4) Coefficients of lift Vs angle of attack. 5) Coefficient of drag Vs angle of attack. 6) CD Vs CL. 1.2 1 0.8 0.6 CL 0.4 CD 0.2 0
‐20
‐10
‐0.2
0
10
20
30
‐0.4
Result:
Thus, the characteristics of symmetrical, cambered airfoil and bluff bodies were studied and the graphs are plotted between CL and α.
EXP NO: - 6 PRESSURE DISTRIBUTION OVER ROUGH AND SMOOTH CIRCULAR CYLINDER Aim:-
To study the pressure distribution over rough and smooth circular cylinders. Apparatus:-
1) Low speed wind tunnel 2) Multi-tube Manometer 3) Smooth and rough circular Cylinder model Formulas used:Coefficient of pressure at port number ’x’ is given by: C px =
(p∞ - px) / (p0 - p∞) = (px - p∞) / q∞
Note: po = p∞ + (1/ 2) ρV
2
po - p∞ = (1/ 2) ρV = q∞ 2
Procedure:-
1. Prepare the low speed wind tunnel as per the instruction for the pressure distribution. 2. Ensure proper electrical installation and other safety. 3. Ensure proper and adequate power supply. 4. Fix the cylinder in the test section over which the pressure distribution is is to be studied. 5. Connect the tubes bundle from multitube multitube manometer to the corresponding tubes in the cylinder model. 6. Switch on the tunnel for few minutes to to warm up. 7. Now set the required velocity of airflow airflow using DC motor motor controller knobs and observe the displacement of the manometer liquid in all tubes, standing at different levels and note them down. 8. Note the manometer readings for different different velocities to get required Cp.
Tabulation for Smooth Cylinder
S.No
Port No.
Cpx = (px - p∞) / q∞
1
1
0.573286
2
2
-0.39413
3
3
-0.41205
4
4
-0.41205
5
5
-0.51954
6
6
0.340389
7
7
0.017915
8
8
-0.41205
9
9
0.143322
10
10
-0.37622
11
11
0.44788
12
12
0.985336
Cylinder 1.2 1 0.8 0.6 0.4 0.2
Cylinder
0
‐0.2 0 ‐0.4 ‐0.6 ‐0.8
5
10
Along the cylinder surface
15
Tabulation for Rough Cylinder
S.No
Port No.
1
1
2
2
3
3
4
4
5
5
6
6
7
7
8
8
9
9
10
10
11
11
12
12
Cpx = (px - p∞) / q∞ 0.573286 -0.39413 -0.41205 -0.41205 -0.51954 0.340389 0.017915 -0.41205 0.143322 -0.37622 0.44788 0.985336
Cylinder 1.2 1 0.8 0.6 0.4 0.2
Cylinder
0
‐0.2 0
2
4
6
8
10
12 12
14 14
‐0.4 ‐0.6 ‐0.8
Along the cylinder surface Result:-
Thus the pressure distribution over a smooth and rough circular cylinder is calculated and the graph is plotted.
EXP NO: - 7 PRESSURE DISTRIBUTION OVER SYMMETRIC & CAMBERED AEROFOIL AND ESTIMATION OF CL AND CD Aim
To study the pressure distribution over a symmetric and cambered aerofoil and find out the lift and drag coefficient. Apparatus:-
1) Low speed wind tunnel 2) Multi-tube Manometer 3) Symmetric and cambered aerofoil model Formulas used:Coefficient of pressure at port number ’x’ is given by:
Cp = (p∞ - pi) / (p0 - p∞) = (px – pi) / q∞ Note: po = p∞ + (1/ 2) ρV
2
po - p∞ = (1/ 2) ρV = q∞ 2
Also C N=(CPL – CPU)dx/c CL=C N Cosα CD = C N Sinα Procedure:-
1. Prepare the low speed wind tunnel as per the instruction for the pressure distribution. 2. Ensure proper electrical installation and other safety. 3. Ensure proper and adequate power supply. 4. Fix the aerofoil in the test section over which the pressure distribution distribution is to be studied. 5. Connect the tubes bundle from multitube multitube manometer to the corresponding tubes in the aerofoil model. 6. Switch on the tunnel for few minutes to to warm up. 7. Now set the required velocity of airflow airflow using DC motor motor controller knobs and observe the displacement of the manometer liquid in all tubes, standing at different levels and note them down. 8. Note the manometer readings for different different velocities to get required Cp.
Tab lation for symmetric erofoil
S.No
Port No.
Cpx = (px - p ) / q
1
1
0.573286
2
2
-0.39413
3
3
-0.41205
4
4
-0.41205
5
5
-0.51954
6
6
0.340389
7
7
0.017915
8
8
-0.41205
9
9
0.143322
10
10
-0.37622
11
11
0.44788
12
12
0.985336
∞
Cp lot for Sy metric aerofoil
Along t e chord le gth
∞
Tab lation for ambered a rofoil
S.No
ort No.
Cpx = ( x - p ) / ∞
∞
1
1
0.573286
2
2
-0.3 413
3
3
-0.41205
4
4
-0.41205
5
5
-0.51954
6
6
0.340389
7
7
0.017915
8
8
-0.41205
9
9
0.143322
10
10
-0.3 622
11
11
0.4 788
12
12
0.985336
p Plot for he Cambe ed aerofoil
Along the chord le ngth Res lt:-
Thus the pressur distributio over a Sy metric an Cambered Cambered aerofoi aerofoill is calculated calculated a d the g aph is plotted
EXP. NO: - 8 STUDY OF CALIBRATION OF SUPERSONIC WIND TUNNEL Aim
To estimate the efficiency of Supersonic wind tunnel Apparatus Required
Supersonic wind tunnel Manometer Pitot tube
Formulas Used:Coefficient of pressure at port number ‘x’ is given by:
Cpx = (2/ γM ∞) [(px/p∞)-1] 2 (γ/γ-1) (po/p∞) = [1 – (( γ-1)/2)M ∞] 2
Procedure:Study of calibration of supersonic wind tunnel is done in 3 methods 1. Determining by Mach number:a) Run the tunnel b) For a particular pressure take Manometer readings c) Then calculate the Mach numbers at each port. b) See the Mach number in the test sections should be equal. 2. Measuring pitot pressures 1. Connect the Pitot tube in test section 2. Connect the wall static to the manometer 3. Run the tunnel 4. Take the manometer reading 5. See that Mach number in the test section should be equal in all the places 3. Measuring static pressures 1. Take the cross section of the supersonic wind tunnel. 2. Directly measure the length from throat to each port. 3. Take height at each port. 4. Calculate the Mach number theoretically. RESULT: Thus the calibration of supersonic wind tunnel is studied and its efficiency is estimated
EXP. NO: - 9 VELOCITY DISTRIBUTION IN NOZZLE USING SUPERSONIC FREE JET Aim
1. To study the jet decay characteristics along the jet axis 2. To obtain lateral spread characteristics of the jet.
APPARATUS REQUIRED
Free-jet test setup, Traverse mechanism, Pitot probe for total pressure measurements, utube Mercury manometer and meter scale, Barometer, Thermometer.
THEORY
Jets can be classified in a variety of ways. They can be classified as compressible or incompressible jets based on the speed of the jet. They can also be classified as laminar or turbulent jets based on the Reynolds number. Based on the jet cross section shape, they are classified as circular or non-circular jets. Jets come under the category of free shear flows. Jets which have free and unconstrained boundaries are called free jets. Examples are nozzle exhaust jet into atmosphere, water jet issuing from a conduit or a tap etc. The flow of a jet can be divided into two regions; the mixing region and the potential core. c ore. The potential core is that portion in the centre c entre of the jet and near the exit ex it of the orifice through which the jet flows. In the potential core, the viscous effects are negligible and the fluid can be considered to be inviscid. The first part of the mixing region is the boundary of the jet near the exit of the nozzle. This mixing region widens as the flow goes downstream. Far downstream, the whole jet will be a mixing region. In the mixing region, the effects of viscosity and heat conduction have to be considered. In the mixing region there are large variations in velocity and density.
DESCRIPTION OF EXPERIMENTAL SET-UP
The experimental set-up consists of a converging-diverging (CD) nozzle connected to a high pressure compressor tank. The high pressure air is passed into the CD nozzle through a moisture separator, dust collector and a pressure regulating valve to control the mass flow rate through the duct. To laminarize the flow, three meshes are fitted inside the diverging duct. The duct also consists of a settling chamber to which CD nozzle is attached and the compressed air coming out as a free- jet into the open atmosphere. The speed of the free-jet can be controlled by controlling the mass flow rate through the pressure regulating valve.
CONDUCTING EXPERIMENT
In this experiment, the variation of jet total pressure along the centerline of a free jet is measured to understand its decay characteristics. The jet is of circular shape. To find its lateral spread characteristics the total pressure variations in the lateral direction ie. Direction at different X positions i.e. X = 1, 2, 3, 4 … are measured. The total pressure pressure probe is mounted in a traversing mechanism, which ensures the movement of the probe along the jet axis.
CALCULATIONS
Velocity calculations:
Where, P0 is the total pressure P is the static pressure M is the Mach number
γ is the specific heat ratio ( fir air γ = 1.4)
DISTAN DISTAN MANOM CE CE ETER AL ONG AL ONG READIN X-AXIS Y-AXIS G in in(cm) in(cm) (cm)
Mach No
0
13.5
0.49
17 1 70.86
0
3
13
0.48
16 167.84
6
11
0.45
155.05
9
7.2
0.36
12
2.8
14
0
1
2
3
4
5
DISTAN DISTAN MANOM CE CE ETER Velocity AL ONG AL ONG READIN m/s m/ s X-AXIS Y-AXIS G in in(cm) in(cm) (cm)
Mach No
Velocity m/s m/ s
5.9
0.33
11 1 14.82
3
5.4
0.32
10 109.97
6
5
0.30
105.92
12 126.48
9
4.3
0.28
98.38
0.23
79.66
12
3
0.24
82.42
2.4
0.21
73.82
14
2.6
0.22
76.80
0
10.5
0.44
15 1 51.65
0
5.4
0.32
10 1 09.97
3
9.9
0.42
147.44
3
5
0.30
105.92
6
7.9
0.38
13 132.28
6
4.5
0.29
10 100.60
9
5.5
0.32
11 110.96
9
3.5
0.26
88.92
12
4
0.27
94.95
12
2.7
0.22
78.24
14
3
0.24
82.42
14
2.4
0.21
73.82
0
12.9
0.48
16 167.23
0
5
0.30
10 105.92
3
12.2
0.47
16 1 62.87
3
4.8
0.30
10 1 03.82
6
7.2
0.36
12 126.48
6
3.9
0.27
93.78
9
5.4
0.32
10 109.97
9
3.5
0.26
88.92
12
3.9
0.27
93.78
12
2.5
0.22
75.32
14
2.9
0.23
81.05
14
2
0.19
67.45
0
8.2
0.39
13 134.68
0
4.3
0.28
98.38
3
7.4
0.37
128.17
3
4
0.27
94.95
6
6.2
0.34
11 117.63
6
3.7
0.26
91.38
9
5
0.30
105.92
9
3.4
0.25
87.66
12
2.8
0.23
79.66
12
3
0.24
82.42
14
2.7
0.22
78.24
14
2.2
0.20
70.71
0
7.4
0.37
128.17
0
4
0.27
94.95
3
6.8
0.35
12 123.02
3
3.7
0.26
91.38
6
5.5
0.32
11 110.96
6
3.4
0.25
87.66
9
4.5
0.29
10 100.60
9
2.8
0.23
79.66
12
3.4
0.25
87.66
12
2.2
0.20
70.71
14
2.6
0.22
76.80
14
1.8
0.18
64.02
0
6.5
0.35
120.36
3
6.2
0.34
117.63
6
5
0.30
105.92
9
4.1
0.28
96.11
12
3.2
0.24
85.08
14
2.4
0.21
73.82
6
7
8
9
10
From the above formula find out the Mach number. M = u/a
a= Where T is the Lab temperature So u = Ma TABULATION
Sl.No
Distance along jet axis in cm cm
Difference in heights ∆h
in cm
Mach Number
Jet velocity in m/s
1
2 3 4 5
PLOTS AND DISCUSSION
1. Variations of total pressure and local reference velocity with distance along centerline of the jet 2. Variations of total pressure and local reference velocities in lateral direction at different X values. 3. Comparisons of velocity profiles in lateral direction of the jet at different X values.
Result:
Thus the jet decay characteristics along the jet axis and lateral spread characteristics of the jet are studied with graphs.
EXP. NO: - 9 FLOW VISUALIZATION USING SHADOWGRAPH SYSTEM Aim:-
To visualize the flow pattern in supersonic flow. Apparatus Required
Supersonic free jet Converging Diverging Nozzle Shadow graph System Camera Introduction
Flow visualization has played an important role in understanding the fundamentals of fluids phenomena. One of the most important applications of flow visualization was due to Osborne Reynolds, a prominent innovator in fluid dynamics, in 1883. He investigated the circumstances of the transition from laminar to turbulent flow by injecting a liquid dye into the water flowing through a long horizontal pipe. From these experiments came the famous dimensionless Reynolds number for dynamic similarity. Another powerful flow visualization tool is schlieren/shadowgraph technique, which is able to visualize 'invisible' density gradients and has been applied widely to study combustion, aerodynamics, fluid mechanics, etc.
Experimental Procedure
It consists of a light source which can be varied its intensity, lenses, screen and cameras. Direct shadowgraph is shown in figure.
Shadowgraph image
Difference between Shadowgraph and Schlieren systems Sl. No.
Shadowgraph
Schlieren
1
Displays a mere shadow
Displays a focused image
2
Shows light ray displacement
Shows ray refraction angle,
3
Illuminance level responds to
4
No knife edge used
2n x2
Illuminance level responds to Knife edge used forcutoff
n x
Result:
Thus the study of shadow graph system is studied and the shadow graph image is taken.
EXP NO: - 11 PRESSURE DISTRIBUTION OVER WEDGE AEROFOIL AND ESTIMATION OF CL AND CD Aim:-
To study the pressure distribution over a Wedge aerofoil. Apparatus:-
1) Low speed wind tunnel 2) Multi-tube Manometer 3) Wedge aerofoil model Formulas used:Coefficient of pressure at port number ’x’ is given by:
Cp = (p∞ - pi) / (p0 - p∞) = (px – pi) / q∞ Note: po = p∞ + (1/ 2) ρV
2
po - p∞ = (1/ 2) ρV = q∞ 2
Also C N=(CPL – CPU)dx/c CL=C N Cosα CD = C N Sinα Procedure:1. Prepare the low speed wind tunnel as per the instruction for the pressure distribution on the Wedge aerofoil. 2. Ensure proper electrical installation and other safety. 3. Ensure proper and adequate power supply. 4. Fix the aerofoil in the test section over which the pressure distribution distribution is to be studied. 5. Connect the tubes bundle from multitube multitube manometer to the corresponding tubes in the aerofoil model. 6. Switch on the tunnel for few minutes to to warm up. 7. Now set the required velocity of airflow airflow using DC motor motor controller knobs and observe the displacement of the manometer liquid in all tubes, standing at different levels and note them down. 8. Note the manometer readings for different different velocities to get required Cp.
Tab lation :-
.No
Port No.
Cpx (px - p ) / q ∞
∞
1
1
0.573286
2
2
- .39413
3
3
4
4
- .41205
5
5
- .51954
6
6
0.340389
7
7
0.017915
8
8
- .41205
9
9
0.143322
10
10
- .37622
11
11
.44788
12
12
- .41205
0.985336
We ge aeroflil
A ong the ch rd length Res lt:Thus the pressur distributio over Wed e aerofoil i calcula calculated ted and and the gra gra h is plotte plotted. d.
