Useful for aeronautical Engineering stud

Nice ppt

1. Wind Tunnel Aerodynamics
By
Dr. Charles Trefny
20 Sept 2002

2. Aerodynamics
The field of science and engineering
dealing with the effects of air moving
around solid objects.

3. Aerodynamicists
Predict what will happen in a given
situation using physical laws, math,
wind-tunnels and computers

4. Air has mass and obeys Newton’s laws.
100 gallons of air has a mass of about 1 pound.
We must speed-up, slow-down, or change the
direction of the air to generate a force.
Look for this in the following examples of
aerodynamics…

17. Wind tunnels are used to predict the amount of
force generated by solid objects.
This helps aerodynamicists choose the proper
size for things such as wings, spoilers, and
parachutes.
Information obtained in wind tunnels is used to
improve the design of anything affected by
wind.
Wind-Tunnels come in all shapes and sizes…

18. Open-Return Type Wind-Tunnel

20. Closed-Return Type Wind-Tunnel

28. Blow-Down Type Tunnel

30. Wind Tunnel Test Examples

51. Similarity Principle
Allows us to test a small model and get
information about the full-size object
We’ll use a parachute for example…

52. Will the egg break?…

53. Similarity Principle:
For similar shapes, this ratio always comes
out to the same number.
Weight
Density x Speed x Speed

x Diameter x Diameter
Don’t worry, it’s just a FRACTION!!!

54. Density x Speed
2
x Diameter
2
= C
Weight

55. Density x Speed
2
x Diameter
2
C =
Do a wind tunnel test to find out what “C” is
for the parachute
Weight
All “known” in the
wind tunnel!

56. Computers can also be used to solve
problems in aerodynamics.
The computer solves complex mathematical
equations that are based on Newton’s laws of
motion
The wing or “airfoil” is a classic problem…