subsonic wind tunnel design methodology

1. Subsonic wind tunnel
design methodology
By
ANIRUDH B
11MN01

2. What is a wind tunnel?
Wind tunnels are measurement tools to study gas flows around
a body and the forces generated by the gas-body interaction
Mostly air is used in wind tunnels
Using such tool it is possible to measure global and local flow
velocities, as well as pressure and temperature around the body

3. Components of a wind tunnel
Bell mouth section/Nozzle Fine screen mesh

4. Components of a wind tunnel
Diffuser section with a
Test chamber
Suction fan located at
The left of the diffuser

5. Wind tunnel Design
Closed circuit wind tunnel

6. Wind tunnel Design
Test Chamber: Dimensions, shape and air velocity

7. Wind tunnel Design
Test Chamber: Dimensions, shape and air velocity
*

8. Wind tunnel Design
Nozzle: Area ratio

9. Wind tunnel Design
Nozzle: Area ratio
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10. Wind tunnel Design
Nozzle: Area ratio
*

11. Wind tunnel Design
Nozzle: Area ratio

12. Wind tunnel Design
Second Diffuser

13. Wind tunnel Design
Second Diffuser: Inlet cross sectional area
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14. Wind tunnel Design
Second Diffuser: Inlet cross sectional area
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15. Wind tunnel Design
Second Diffuser: Inlet cross sectional area
*

16. Wind tunnel Design
Shape adapter: Length
Shape adapter is also designed and its total Length equals 0.3m

17. Wind tunnel Design
First Diffuser: side l of the outlet CS area
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18. Wind tunnel Design
First Diffuser: side l of the outlet CS area

19. Wind tunnel Design
First Diffuser: side l of the outlet CS area
*

20. Wind tunnel Design
Corners: small corners and large corners
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21. Wind tunnel Design
Corners: small corners and large corners
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22. Wind tunnel Design
Settling chamber
Settling chamber consists of honeycombs and mesh screen to
reduce the flow turbulence before it enters the nozzle.

23. Wind tunnel Design
Settling chamber: honeycomb
Key design factors are:
1) Length
2) Hydraulic diameter
3) porosity

24. Wind tunnel Design
Settling chamber: honeycomb

25. Wind tunnel Design
Settling chamber: honeycomb

26. Wind tunnel Design
Settling chamber: honeycomb

27. Wind tunnel Design
Settling chamber: screens
To have effective reducing in
turbulence the porosity must
lie between 0.58 to 0.8
Different mesh qualities
(coarse, medium, f ine)
are efficient than single fine
mesh

28. Wind tunnel Design
Pressure losses
1) Pressure loss in constant cross section area sections (friction)
2) Pressure loss in diffusers (friction and expansion)
3) Pressure loss in corners (friction and expansion)
4)Pressure loss in screens(porosity or its complement solidity, the Reynolds number
Calculated with wire diameter, and mesh factor)
5) Pressure loss in honeycombs (length to cell hydraulic diameter ratio,
porosity and Reynolds number)
6) Pressure loss in nozzles (skin friction)

29. Wind tunnel Design
Fan selection

30. Summary
The design procedure consists of the following main steps:
1. Defining the test section dimensions and desired flow velocity by test type;
2. Wind tunnel component design by test section criteria;
3. Wind tunnel component pressure loss calculation;
4. Determining pressure loss throughout the wind tunnel circuit as a function
of the possible flow velocity in the testing section in both open and closed
configurations;
5. Matching wind tunnel components to commercial fans, and energy
considerations.

31. References:
1)Justin D Periera, “Wind tunnels-Aerodynamics, models and experiments”,
Nova science publishers
2) Metha R. D., Bradshaw P. “Design Rules for Small Low Speed Wind Tunnels”
Journal of Royal Aeronautical Society 1979, Vol. 73.
3)Wind tunnel design and wind tunnel parts-NASA