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1. NASA Glenn Research Center
Icing Branch - Van Zante / Dynacs Page 1
Wind Tunnel Experiments for Grades 8 - 12
Wind Tunnel Experiments
for
Grades 8 - 12
Dr. Judy Foss Van Zante
Dynacs Engineering Co., Inc.
Cleveland, OH
6/15/99

2. NASA Glenn Research Center
Icing Branch - Van Zante / Dynacs Page 2
Wind Tunnel Experiments for Grades 8 - 12
Contents
Sample Experiments 3
Governing Equations 15
Flow Visualization Techniques 19
How to Make the Measurements 24
Background - Why Test in Wind Tunnels 27
Selected References 31

3. NASA Glenn Research Center
Icing Branch - Van Zante / Dynacs Page 3
Wind Tunnel Experiments for Grades 8 - 12
Sample Experiments

4. NASA Glenn Research Center
Icing Branch - Van Zante / Dynacs Page 4
Wind Tunnel Experiments for Grades 8 - 12
Ideas for Wind Tunnel Experiments
Model: Airfoil or Flat Plate
• L vs.  Lift vs. Angle of Attack
• L vs. VLift vs. Velocity
• C
D
vs. ReDrag vs. Reynolds Number
i.e., vary Speed and/or Size
• Investigate the effects of contamination on
the leading edge (sand paper, paper mache) to
mimic ice accretion, bug splat, etc...This should
reduce max lift & increase drag.

5. NASA Glenn Research Center
Icing Branch - Van Zante / Dynacs Page 5
Wind Tunnel Experiments for Grades 8 - 12
Wind Tunnel Test Section with Airfoil
Mounting Options
Airfoil on Sting Wall-Mounted
Flow

6. NASA Glenn Research Center
Icing Branch - Van Zante / Dynacs Page 6
Wind Tunnel Experiments for Grades 8 - 12
Lift vs. Angle of Attack
As the angle of attack
increases, so should the lift
- until a certain point (the
stall angle of attack).
Angle of attack ():
angle between flow and
chord line.
Chord line:
straight line between most
forward and most aft points


Lift
Flow

7. NASA Glenn Research Center
Icing Branch - Van Zante / Dynacs Page 7
Wind Tunnel Experiments for Grades 8 - 12
scale
Lift vs. Angle (cont.)
Angle
L
i
f
t
Visual: See airfoil lift
as angle increases
Measure: airfoil lift as
a function of angle

8. NASA Glenn Research Center
Icing Branch - Van Zante / Dynacs Page 8
Wind Tunnel Experiments for Grades 8 - 12
Wind Tunnel Experiment
Lift vs. Angle Worksheet

9. NASA Glenn Research Center
Icing Branch - Van Zante / Dynacs Page 9
Wind Tunnel Experiments for Grades 8 - 12
Lift vs. Velocity
As the velocity (speed)
increases, so should the lift.
Note: Keep the angle of
attack constant.
The greater the angle (prior
to stall) the greater the
change in lift.
Lift
Velocity
(Speed)

10. NASA Glenn Research Center
Icing Branch - Van Zante / Dynacs Page 10
Wind Tunnel Experiments for Grades 8 - 12
Lift vs. (Velocity)
2
Velocit
y
L
i
f
t
Visual: See airfoil lift
as speed increases
scale
Measure: airfoil lift as
a function of speed
V
2
L

11. NASA Glenn Research Center
Icing Branch - Van Zante / Dynacs Page 11
Wind Tunnel Experiments for Grades 8 - 12
Wind Tunnel Experiment
Lift vs. Velocity Worksheet

12. NASA Glenn Research Center
Icing Branch - Van Zante / Dynacs Page 12
Wind Tunnel Experiments for Grades 8 - 12
Ideas for Wind Tunnel Experiments
Model: Drag Body
Double Elimination Competitions
Build two objects. In a head-to-head comparison,
see which one has the least drag.
Which way will the object with the most drag
move?
– Race Cars
– Geometric shapes

13. NASA Glenn Research Center
Icing Branch - Van Zante / Dynacs Page 13
Wind Tunnel Experiments for Grades 8 - 12
Wind Tunnel with Drag Objects
Mounting Options
Bluff Bodies Race Cars
Rotating Sting Pulley

14. NASA Glenn Research Center
Icing Branch - Van Zante / Dynacs Page 14
Wind Tunnel Experiments for Grades 8 - 12
Ideas for Wind Tunnel Experiment
Model - Drag Body
Notes:
–The frontal area (the side facing the flow) must be the
same. Drag is directly related to the surface area.
–If using the pivot & sting, objects must be mounted equally
far apart from the pivot point. It is important that each
object has the same moment arm.
–If using the pulley system, it might be better to have two
pulleys.

15. NASA Glenn Research Center
Icing Branch - Van Zante / Dynacs Page 15
Wind Tunnel Experiments for Grades 8 - 12
Governing Equations

16. NASA Glenn Research Center
Icing Branch - Van Zante / Dynacs Page 16
Wind Tunnel Experiments for Grades 8 - 12
Governing Equations
Lift & Drag are equal to the
Dynamic Pressure * Surface Area * Coefficient
These Coefficients are a function of
Angle of Attack, Model Geometry & Mach number
D
2
L
2
C*S*V
2
1
D
C*S*V
2
1
L





17. NASA Glenn Research Center
Icing Branch - Van Zante / Dynacs Page 17
Wind Tunnel Experiments for Grades 8 - 12
Nomenclature
Dynamic Pressure, ½  V
2
 = density (of air); “rho”
V = velocity (speed)
Surface Area, S
S = chord * span
chord is wing length, span is wing width
Coefficient of Lift C
L = function (, model, Ma)
Coefficient of Drag C
D
= function (, model, Ma)

18. NASA Glenn Research Center
Icing Branch - Van Zante / Dynacs Page 18
Wind Tunnel Experiments for Grades 8 - 12
The Lift and Drag can be changed most easily by
changing the angle of attack () or speed (V). Of
course, the surface area (S) can also be
adjusted. If a water tunnel is also available, the
working fluid (), e.g. air to water, can also be a
variable.
During the course of one experiment, it is
important to only change one variable at a time.
Governing Equation
Notes

19. NASA Glenn Research Center
Icing Branch - Van Zante / Dynacs Page 19
Wind Tunnel Experiments for Grades 8 - 12
Flow Visualization
Techniques

20. NASA Glenn Research Center
Icing Branch - Van Zante / Dynacs Page 20
Wind Tunnel Experiments for Grades 8 - 12
Flow Visualization Techniques
Flow Visualization illustrates the flow on
or near the object. On the surface, regions
of reverse flow become visible.
• Yarn Tufts, Tuft Probe, Tuft Grid
• Smoke Wand, Smoke Wire
• Trailing Edge Cone (String & paper cone)

21. NASA Glenn Research Center
Icing Branch - Van Zante / Dynacs Page 21
Wind Tunnel Experiments for Grades 8 - 12
Flow Visualization Techniques
Yarn
• Yarn Tufts - tape ~1” segments of yarn directly to the
surface.
• Tuft Probe - tape ~3” light-weight (and visible) string to end
of rod. Probe the flow.
• Tuft Grid - attach ~1” segments of yarn to a wire mesh
(screen) and place behind object (perpendicular orientation to
the flow)
• Trailing Edge Cone - tape one end of string to paper cone,
and the other end to (spanwise) edge of model. This
illustrates streamwise vorticity, if present. It’s great for delta
wings.

22. NASA Glenn Research Center
Icing Branch - Van Zante / Dynacs Page 22
Wind Tunnel Experiments for Grades 8 - 12
Yarn Tufts on surface
xx

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Tuft Probe
D
e
l t a
W
i n
g
Trailing Edge Cone
Flow Visualization Techniques
Illustrated
Tuft Grid

23. NASA Glenn Research Center
Icing Branch - Van Zante / Dynacs Page 23
Wind Tunnel Experiments for Grades 8 - 12
Flow Visualization Techniques
Cautions
• For yarn & string: If the inertia (mass) of
the yarn/string is too large, it won’t
“follow” the flow.
• For smoke: If the airspeed is too high,
the smoke and air will mix and “blur”.

24. NASA Glenn Research Center
Icing Branch - Van Zante / Dynacs Page 24
Wind Tunnel Experiments for Grades 8 - 12
How to Make the
Measurements

25. NASA Glenn Research Center
Icing Branch - Van Zante / Dynacs Page 25
Wind Tunnel Experiments for Grades 8 - 12
Measuring Lift
•For airfoil and sting: measured from the scale
(ounces). W
t0
= weight at zero velocity.
L = W
t0
– W
t
Caution: try to minimize the friction (binding) at the
tunnel/sting interface, e.g., with a brass bearing.
•For wall mounted: measured from a load cell.
Caution: this is a non-trivial pursuit.
Wind Tunnel Experiment Details

26. NASA Glenn Research Center
Icing Branch - Van Zante / Dynacs Page 26
Wind Tunnel Experiments for Grades 8 - 12
Wind Tunnel Experiment Details
Measuring Velocity
• Pitot-static tube
P = P
total - P
static
Bernoulli’s Equation: P = (1/2) V
2
,  1 kg/m
3
(units!)
V =  2* P/

• Three-cup anemometer

27. NASA Glenn Research Center
Icing Branch - Van Zante / Dynacs Page 27
Wind Tunnel Experiments for Grades 8 - 12
Background
Why Test in Wind Tunnels?

28. NASA Glenn Research Center
Icing Branch - Van Zante / Dynacs Page 28
Wind Tunnel Experiments for Grades 8 - 12
Why Test in Wind Tunnels?
The Ultimate Goal: to Understand the Fluid
Mechanics or Aerodynamics of an
•Aircraft in Flight
•Submarine in Water
•Automobile on Road
•New Structure (Building, Bridge) in City
How do you get There from Here?
•Build a model and test it
–In a Wind Tunnel
–On a Computer

29. NASA Glenn Research Center
Icing Branch - Van Zante / Dynacs Page 29
Wind Tunnel Experiments for Grades 8 - 12
Two of NASA’s Wind Tunnels
Ames 80’ x 120’
Langley

30. NASA Glenn Research Center
Icing Branch - Van Zante / Dynacs Page 30
Wind Tunnel Experiments for Grades 8 - 12
Types of Wind Tunnels
Full Scale / Full Geometry(1999 price estimates)
•NASA Glenn 10’ x 10’ Supersonic $2000/hr
•NASA Ames 80’ x 120’ $1000/hr
Sub-Scale / Single Component
•NASA Glenn 20” x 30” Low Speed $2/hr
How does one scale a model?
•Geometric
•Dynamic (e.g. Reynolds Number, Re =
UL/

31. NASA Glenn Research Center
Icing Branch - Van Zante / Dynacs Page 31
Wind Tunnel Experiments for Grades 8 - 12
Selected References
Aerodynamics
1.Abbott, Ira A. & von Doenhoff, Albert E., “Theory of Wing Sections,” Dover Publications, 1959.
2.Anderson, John D., “Fundamentals of Aerodynamics,” McGraw-Hill, Inc., 2nd Ed., 1991.
3.Anderson, John D., “Introduction to Flight,” McGraw-Hill, Inc., 3rd Ed., 1989.
4.Shevell, Richard S., “Fundamentals of Flight,” Prentice-Hall, Inc., Englewood Cliffs, NJ, 1983.
Fluid Mechanics
5.Potter, Merle C. & Foss, John F., “Fluid Mechanics,” The Ronald Press Co., NY, 1975 (now
published by Great Lakes Press).
6.White, Frank M., “Fluid Mechanics,” McGraw-Hill Inc., 2nd Ed., 1986.
7.Shapiro, Ascher H., “Shape and Flow: The Fluid Dynamics of Drag,” Science Study Series, Anchor
Books, Doubleday & Co., Inc.,Garden City, NY, 1961.
Flow Visualization
8.Van Dyke, Milton, “An Album of Fluid Motion,” Parabolic Press, P.O. Box 3032, Stanford, CA
94305-0030, 1982.
9.Japan Society of Mechanical Engineers, “Visualized Flow,” Pergamon Press, 1988.
10.National Committee for Fluid Mechanics Films, “Illustrated Experiments in Fluid Mechanics,” The
MIT Press, Cambridge, MA and London, England, 1972.