1. ME 388 – Applied Instrumentation Laboratory Wind Tunnel Lab

2. References Munson, Young and Okiishi, Fundamentals of Fluid Mechanics
Zucker, Fundamentals of Gas Dynamics
Zucrow and Hoffman, Gas Dynamics
Any fluids text

3. Experimental Objectives
Measure lift and drag forces
NACA 0012 airfoil (National Advisory Committee on Aeronautics)
At various angles to air stream
Determine coefficients of lift and drag and compare to published values
Determine coefficients of lift and drag at the stall angle

4. Wind Tunnel Testing
Allows engineers to predict the amount of lift and drag that airfoils can develop in various flight conditions.
A 747 aircraft can weigh over 200,000 lbs.

5. 2D Components of Lift and Drag
Resultant force due to airflow across an asymmetric body is not in the direction of the airflow

6. Lift
Generated by pressure difference over the airfoil when the air moving over the body takes a different path to reach the same point

7. Drag
Result of fluid friction
Opposes body motion

8. Lift and Drag Dependence
Size
Shape
Fluid flow
Principle of Similitude allows us to “non-dimensionalize” these parameters

9. Wind Tunnel and Instrumentation

10. NACA 0012 Air Foil

11. Scaled-down Physical Modeling
Consider size for a given shape

14. Lift and Drag Plots

16. Lab Measurements Drag and Lift forces are measured with a dynamometer
Chord and width are measured with a ruler
Air velocity is measured with a Pitot tube
Angle of attack is measured with a protractor

17. Fluid Conditions For similitude, fluid conditions must also be similar
Fluid flow is non-dimensionalized via the Reynolds number

18. Pitot Tube and Bernoulli Eqn.
Frictionless flow with only mechanical energy
No heat transfer
No change in internal energy

19. Calibrate Dynamometer

20. Calibration Procedure
Remove air foil from dynamometer post
Attach string and weights from dynamometer post and calibrate (use weights to at least 1000 g)
Remove weights and turn-on wind tunnel and adjust for air velocity for Re = 160,000
Record voltages from dynamometer
Turn-off air and re-install air foil
Record voltage (weight) of airfoil
Run experiment

21. Dynamometer Calibration Curves

22. Experimental Procedure
Let dynamometer heat-up 15 minutes before taking data
Adjust airfoil to 0° attack angle and take dynamometer reading
Take readings every 3°
When lift force decreases (voltage drops), decrease attack angle in 1° increments to determine stall angle

23. Lab Requirements Summary
Develop dynamometer calibration curves
Plot lift and drag coefficients as a function of attack angle
Compare data to published NACA 0012 data at Re = 160,000, and for a flat plate
Determine angle of maximum lift, a.k.a. the stall angle
Calculate uncertainty of the lift coefficient at the stall angle

24. In 1915, the U.S. Congress created the National Advisory Committee on Aeronautics (NACA -- a precursor of NASA). During the 1920s and 1930s, NACA conducted extensive wind tunnel tests on hundreds of airfoil shapes (wing cross-sectional shapes). The data collected allows engineers to predictably calculate the amount of lift and drag that airfoils can develop in various flight conditions. Reference?

25. NASA Photo