PART – A (10 x 2 = 20)
Answer All the Questions
1. Define Reynolds number?
2. Define Mach number?
3. What is meant by subsonic
and transonic speed regime?
4. Define critical Mach number?
5. Name any two equipments used
in the calibration of wind tunnels.
6. What is meant by LDA?
7. What is meant by PIV?
8. Name any two equipments used
for the measurement of force?
9. How are the surface
streamlines and turbulence measured in wind tunnels?
10. What is the technique
adopted to visualize Shock waves.
PART – B (5 x 16 = 80)
Answer All the Questions
11. Explain the Buckingham’s Pi
Theorem.
(or)
12. Briefly discuss the scale
effects of similarities.
13. Discuss the classification
of wind tunnels in detail.
(or)
14. Explain with a neat diagram
the layout of a subsonic wind tunnel.
15. Explain the techniques used
for Turbulence measurements in a wind tunnel.
(or)
16. Explain in detail the
calibration of a supersonic tunnel.
17. Explain with a neat sketch
the working of a hot wire anemometer.
(or)
18. Briefly explain the
measurement of pressure, velocity and force in a wind tunnel.
19. Discuss the smoke and tuft
grid techniques used for flow visualization.
(or)
20. Briefly explain the optical
methods used for flow visualization.
PART - A (10 X 2 = 20)
Answer ALL the Questions
1. Explain the term dynamic
similarity.
2. Define Mach number.
3. Define laminar and turbulent
flow.
4. What are the classifications
of wind tunnel?
5. Name any two equipments used
in the calibration of wind tunnels.
6. Define horizontal buoyancy.
7. What is meant by LDA?
8. Name any two equipments used
for the measurements of velocity.
9. How are the surface
streamlines and turbulence measured in wind tunnels?
10. What is meant by PIV?
PART – B (5 x 16 = 80)
Answer All the Questions
11.
Explain the Buckingham’s Pi theorem.
(or)
12. Explain the dynamic
similarity between a wind tunnel model and the prototype to be flight-tested.
What are the essential conditions to be satisfied for the results to be carried
from the model to the prototype? Are there any limitations or preconditions
involved?
13. What is understood by the
term low speed wind tunnel in aerodynamic testing? Describe with brief details
through sketches and plots, various types of low speed wind tunnels based upon
the details of the flow in test section.
(or)
14. Write notes on:
(a) setting Mach number in a
transonic wind tunnel
(b) Measurements of turbulence
level in a transonic wind tunnel. Explain the techniques used for turbulence
measurements in a wind tunnel.
15. Describe the basis for the
measurement of pressure and instruments used for the purpose. What are its
advantages and applications? Illustrate with theory and an example. It is
desired to obtain pressure distribution of a rotating circular cylinder kept in
the test section of a wind tunnel.
(or)
16. Explain in detail the
calibration of a supersonic wind tunnel.
17. Explain with a neat sketch
the working of a hot wire anemometer.
(or)
18. What types of wind tunnel
balances are used to ascertain forces and moments on an airplane model in a low
speed wind tunnel? Hence describe the underlying principles of an external type
wind tunnel balance for measuring lift, drag and pitching moments over a finite
span wing.
19. Explain the phenomenon of
separation of flow over a 2D wing with the help of liquid paraffin generated
smoke wire technique with good sketches. What are its merits over kerosene
generated smoke?
(or)
20. Briefly explain the optical
methods used for flow visualization.
PART – A (10 x 2 = 20)
Answer All the Questions
1. What is geometrical
similarity in wind tunnel testing of models?
2. What is boundary layer
correction in the test section design of wind tunnels?
3. What is turbulence factor of
a subsonic wind tunnel?
4. How is test section speed
measured in case of a subsonic wind tunnel?
5. How are wind tunnel balances
classified?
6. What is the basic principle
involved in the interferometer method of flow visualization?
7. What are the advantages of
flow visualization methods?
8. How is total pressure
estimated in the test section of a super sonic wind tunnel?
9. What is horizontal buoyancy?
10. What are the limitations of
dye injection method for flow visualization?
PART
– B (5 x 18 = 60)
Answer All the Questions
11. (a) State Buckingham
theorem. How is thus theorem useful in the experiments using wind tunnels?
(b) What is the basic principle
behind hot wire anemometer? What are its limitations?
(or)
12. Define the following
non-dimensional numbers: force coefficient, Euler number, Reynold’s number and
moment coefficient. How do the model scale effects influence the wind tunnel
test results?
13. How are the wind tunnels
classified? What are the special problems of testing in hypersonic wind
tunnels?
(or)
14. Sketch the typical layout
of a supersonic wind tunnel and mark all the components and subsystems. What is
starting problem in supersonic tunnels?
15. Write short notes on the
following topics:
(a) Flow angularities in
wind-tunnel testing.
(b) Turbulence intensity
measurements in wind tunnel test section.
(or)
16. With a neat illustration
explain the objective of calibration of a wind tunnel. In what way the
calibration procedure for a supersonic tunnel different from that of a subsonic
wind tunnel?
17. Distinguish between
internal and external wind tunnel balances. Briefly explain how force
measurements are carried out using an external strain gauge balance.
(or)
18. Bring out the essential
features of a strain gauge based six component internal wind balance. Explain
how the six components are measured using the balance.
19. With neat illustration
explain the basic principles of Schelieren method of flow visualization. What
are the advantages and limitations of the method?
(or)
20. Write short notes on the
following techniques:
(a) Smoke technique for flow
visualization.
(b) Use of tufts and electrical
techniques for flow visualization studies.
B.Tech I Semester Regular Examinations, November 2006
WIND TUNNEL TECHNIQUIES (Aeronautical Engineering) Time:
3 hours Max Marks: 80
Answer any FIVE Questions All Questions carry equal
marks
1. Explain the term Dynamic similarity in aerodynamic
testing. Does it influence the aerodynamic characteristics of a model under
testing? Hence state the PI theorem and work out dimensionless groups upon
which depend the aerodynamic characteristics of a model under tests in a wind
tunnel. [16] 2. Show with good sketches a comparison of the aerodynamics of a
closed ckt , open jet wind tunnel with an open test section ,open ckt wind
tunnel for the same capabilities. Which of the two is economical in the longer
run? Illustrate with reference to operational charges and fabrication cost. [16]
3. Show with a detailed sketch salient features of a continuous type supersonic
wind tunnel. What are its similarities with a continuous, return type subsonic
tunnel; explain with a sketch. [16] 4. You are in the process of designing and
fabricating a new low speed wind tunnel. What is the right location of pressure
taps for conducting experiments for speed setting of this tunnel? Describe
theory and the procedure to be followed in this case. [16] 5. Describe an
electronic manometer for recording pressures simultaneously from multiple
pressure ports with neat sketches. How does it differ from an ordinary multi-
tube manometer? [16] 6. Describe a platform type external balance with line
diagrams and sketches for measuring all six components on airplane and missile
models. Draw good sketches and plots in support of your answer. [16] 7. A tuft
grid is considered a supplementary flow visualization technique and used in
conjunction with smoke flow visualization. Make use of this technique for
explaining flow over a circular cylinder and in its field of influence by
arranging tuft grid as deemed fit. [16] 8. Explain the superiority of oil flow
visualization technique over some other surface flow visualization techniques.
What are the factors that contribute to realistic results from this technique?
Apply this method for viewing stalled flow over a finite span wing model:sting
mounted in the test section in laminar and turbulent flows with pitch-changing
mechanisms and present the results in the form of good sketches.
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