Cover Page for Lab Report – Group Portion
Lift on a Wing
Prepared by Professor J. M. Cimbala, Penn State University
Latest revision: 11 January 2012
Name 1:
___________________________________________________
Name 2:
___________________________________________________
Name 3:
___________________________________________________
[Name 4:
___________________________________________________ ]
Date:
_______________________________
Section number:
ME 325._____
Group letter: (A, B, ...) _____
Score (For instructor or TA use only):
Lab experiment and results, plots, tables, etc. - Procedure portion
Discussion
Neatness & grammar
TOTAL
Comments (For instructor or TA use only):
_____ / 45
_____ / 15
_____ / 10
______ / 70
Procedure and Presentations of Results
A. Calibration of the Electronic Pressure Transducer
1. Follow the same procedure as in the other wind tunnel lab (Drag on Spheres) to calibrate the electronic pressure
transducer. Calibrate such that 1.00 Volts on the Validyne electronic display unit corresponds to exactly 4.00 inches
of water, as previously.
2. Restore the pressure line to the Pitot-static probe so that the electronic pressure transducer measures the wind tunnel
speed, as in the previous lab.
B. Calibration of the Wind Tunnel Lift Balance
1. Follow the same procedure as in the other wind tunnel lab (Drag on Spheres) to calibrate the lift balance, except use
the strain gage indicator marked “Lift”, the string that is labeled LIFT instead of DRAG, and use the computer
program Lift Calibrate instead of Drag Calibrate. The program generates coefficients for the linear least-squares
curve fit. Write those coefficients below:
Slope =
_____________________ N/V
Intercept =
_____________________ N
(5) 2. Program Lift Calibrate keeps a record of all calibration data points in a file that you name. Open this file in Microsoft
Excel, and generate a plot of the lift balance calibration. Show your plot to your instructor or TA for his/her initials
before continuing. Attach the approved plot to your report.
See Figure
.
C. Measurement of Lift on the Model Fin
With the aid of the computerized data acquisition system, you will measure the lift on the model fin at various angles of
attack, and at various Reynolds numbers.
1. If not already in place, install the model fin to the wind tunnel drag/lift balance. Adjust the angle of attack to 0. Be
careful that you don’t over-tighten anything or apply too much force on the model. Consult your instructor or TA if
necessary to clarify the operation of the equipment.
2. Turn on the Toshiba Tosvert 130H1 Transistor Inverter (mounted on the wall). The display should read “OFF”. With
the wind tunnel off, re-zero both the lift balance and the pressure transducer if necessary.
3. A computer data acquisition program called Lift Measure is available for this lab. This program is nearly identical to
the drag measurement program of the other wind tunnel lab, except it measures lift rather than drag. Consult the
instructions of that lab manual if necessary to refresh your memory about using the computer or the wind tunnel. You
will need to enter the barometric pressure, length and area scales, etc., as previously. For the length scale, use the
chord length of the model fin (c = 5.8 in). For the area, enter the planform area in square inches (A = 56.3 in2). You
will also need to enter the name of the lift calibration file that you just created, and a new file name for the lift data.
We suggest a descriptive file name that includes one or more of your group members’ names, and the nominal
Reynolds number for this run, e.g., “Jones_Watson_Smith_Re_100000.txt”.
4. Adjust the wind tunnel speed while taking data until the Reynolds number is close to 100,000. When the Reynolds
number is as close to 100,000 as possible, take several data points (5 are recommended) at this Reynolds number and
angle of attack (zero degrees). Record the blower frequency (on the wall-mounted Toshiba frequency controller) and
the wind tunnel velocity corresponding to this Reynolds number in the spaces below:
Blower frequency and tunnel speed at 0o and at Rec = 100,000: Frequency:
Hz
Velocity:
m/s.
o
5. Increase the angle of attack to 2.5 , using the rotational traverse mounted under the airfoil. Without exiting the Lift
Measure program, enter the new angle of attack in the “Enter Parameters” window. Take several data points, again
keeping the Reynolds number as close to 100,000 as possible. Note that as the angle of attack is changed, the wind
tunnel dial setting may need to be adjusted slightly in order to maintain the correct Reynolds number.
6. Repeat Step 5 for several angles of attack, in increments of 2.5o, up to a maximum angle of attack of 30o. Note that
due to temperature changes in the room, etc., the lift balance zero may drift slightly with time. It is advisable
periodically (every 5 or 10 minutes) to shut off the wind tunnel and re-zero the lift balance. At the maximum angle of
attack, record the blower frequency and wind tunnel velocity corresponding to this Reynolds number:
Blower frequency and tunnel speed at 30o and at Rec = 100,000: Frequency:
Hz
Velocity:
m/s.
(5)
Is the blower frequency different at 30o than that recorded above at 0o angle of attack? (yes or no)
.
Why or why not? (Give a brief explanation of your observations):
(10) 7. Terminate the lift measurement program. Create a table of your data file for the nominal Reynolds number Re c 
100,000 (Microsoft Excel is recommended). The table should be labeled appropriately and attached to your report. At
a minimum, it should contain columns for angle of attack, wind tunnel speed, Reynolds number, lift force, and lift
coefficient. Use only the data points that have the proper Reynolds number – discard the extraneous data.
See Table
.
(10) 8. Repeat Steps 3 through 7 for a Reynolds number of approximately 350,000.
Blower frequency & tunnel speed at 0o at Rec =
: Frequency:
Hz Velocity:
m/s.
Blower frequency & tunnel speed at 30o at Rec =
: Frequency:
Hz Velocity:
m/s.
Generate, print, label, and attach a table of data for this Reynolds number.
See Table
.
9. Turn off the wind tunnel, turn off the Toshiba Tosvert 130H1 Transistor Inverter, and set everything back the way it
was when you started the lab. You are now ready to plot lift coefficient as a function of angle of attack.
Presentation of the Data
Now that you have acquired data at two different Reynolds numbers, and at several angles of attack for both of these
Reynolds numbers, you will generate plots from your files so that the data can be analyzed visually.
(10) 1. Plot lift coefficient CL versus angle of attack  at Reynolds number Rec = 100,000. By plotting these data at the same
nominal Reynolds number together on the same plot, you will show some indication of the repeatability of the
measurements. Use a scatter plot (data points only) rather than a line plot that connects data points. On the same plot,
plot the theoretical lift coefficient as a line (no symbols).
See Figure
.
(5) 2. On the same plot, plot lift coefficient CL versus angle of attack  at Rec = 350,000, using different symbols so that
you can directly compare the data at the two values of Rec.
Discussion
(5)
1.
Theory predicts that the lift coefficient of a wing or fin increases nearly linearly with angle of attack (at small
angles), until the wing stalls. Do your data support this? Does your experimental value of the slope (dCL /dα) agree
with theory? Why or why not?
(5)
2.
Comparing your plots at the two different Reynolds numbers, in what way (if any) does Reynolds number affect
the lift performance of this model fin? Why?
(5)
3.
Predict the performance of the fins on the prototype human powered submarine operating at a speed of 3.0 knots
in seawater. Specifically, predict the maximum lift force to be expected from one of these fins, and the angle at
which you predict that the fins will stall.