Investigation of a Technique for Measuring Dynamic Ground Effect in a Subsonic Wind Tunnel

APPENDIX A Inertial Loads Removal Balance force and moment data for each model in the test facility contained significant inertial loads due to carriage motion and support dynamics. Six accelerometers were placed in an orthogonal layout in order to measure the inertial loads on the model. Prior to a set of runs for each model, a wind-off weight tare and three calibration runs (pitch, yaw, roll) were completed.

The weight tare calculated the weight of the model and provided the system with additional correction factors for the weight factor of each model. Extensive data is available from three normal, two axial, and two side accelerometers. This section addresses the method of correction to the balance loads developed on the latest data.

The calibration run consisted of a wind-off, static run during which the model was bumped or "jogged" in one of three directions (pitch, yaw, roll) to induce inertial loads. The model was kept at a constant height of 50" above the ground and at a constant angle of attack. The data set for these runs was curve fitted in linear and multiple regressions for the optimal removal of inertial loads.

Additional calibration was performed for each acceleration in order to remove a bias or zero offset. This was performed by averaging each acceleration over a 0.5 second (75 sample) period at the beginning of each run (prior to any movement of the mast) and using this value as a zero offset which was subtracted out of all remaining samples per acceleration.

Results of the correction for inertial loads are presented for each force and moment. Subtraction of the inertial loads accounted for the removal of most of the measurable vibrational effects.

Secondary accelerations from coupled velocity terms (2) in equations 7.0-12.0 had a negligible effect on the removal of inertial loads. For tests without significant model velocities, the correlation between the measured loads and associated accelerations provided a measure of errors in the system. Models 6 and 7 show excellent correlation between either normal or axial loads and corresponding accelerations. A spectral analysis exhibits frequencies associated with the inertial loads. In addition, the spectral analysis pinpoints low level noise (at 1 Hz) and higher frequencies (at 60 Hz) which interfered in some cases with the correction. Small variations remaining in the residual load were attributed to the noise level of the signal as well as errors in acceleration measurements.

• External loads imparted on the system from striking it • Impulses in the analog signal not resulting from actual loads • Noise level of the signal • Errors in acceleration measurements IO0 ' Model 6, Run 176 ,'-'- 60 ,,Q m e- :::,!!!, ....

o 20 ',',',', ;', :",t',', ",',:", _4,', _,_ J :, _,.,,, _..

@ I,,I.

,,,,,i,h,,.,:,, ::,,,, ,,. _.,, __7.., ,_,,,., ....

,,,,,%,,,,,, , .,I i,'* /I i !!

m -20 ',',, ,,i, ',', r .', E l_ ,,_:, o Z -60 :' [ ....... No correction m /

L Primary correction

-100 I I I 0 2 4 6 Time (sec) Figure A1. TCA wing inertial loads correction for normal force.

e', m o" o L_ o 5 10 15 20 25 I.K E L_ o Z y = 1.848x - 0.7466 R2= 0.9991 .... 60 - Normal Acceleration, (ft/sec 2) Figure A2. TCA wing correlation between normal force and normal acceleration.

Normal Acceleration

Model 6, Run 176 u u u ,< -2 0 10 20 30 40 50 60 70 Frequency, (Hz) Figure A3. Spectral Analysis of Normal Acceleration.

Normal Force

e-, v 4 .o o 2 m t_

E 0

o Z I I I I I I I -2 0 10 20 30 40 50 60 70 Frequency, (Hz) Figure A4. TCA wing Spectral Analysis of Normal Force, no correction.

Corrected Normal Force

e-, Model 6, Run 176 m .o o 2 ii m t_ A

E 0

o Z -2 I I I I I I I 10 20 30 40 50 60 70 Frequency, (Hz) Figure A5. TCA wing Spectral Analysis of Normal Force, primary correction.

Model 6, Run 176 ..Q 10 i :;,, • .',( ].

,I,,,',,',,ii( _, •, _,.

,,o o

'_ -10 Primary correction

-20 i

0 2 4 6 Time (sec) Figure A6. TCA wing inertial loads correction for axial force.

.

• 2 ii ii ii i l l 2 4 6 y = 1.1103x - 0.3354 R2= 0.9969 Axial Acceleration, (ft/sec 2) Figure A7. Pitch Calibration, Normal Force, secondary correction applied.

Axial Acceleration

u 0.8 0.4 ,,., '_ 0 u u ,< -0.4 0 10 20 30 40 50 60 70 Frequency, (Hz) Figure A8. TCA wing spectral analysis of axial acceleration.

Axial Force

..Q _. 0.8 P 0.4 -- 0 .__ x ,< -0.4 0 10 20 30 40 50 60 70 Frequency, (Hz) Figure A9. TCA wing spectral analysis of axial force, no correction.

Corrected Axial Force

..Q 0.8 0.4 LI.

X I I I I I I I ,,_ -0.4 0 10 20 30 40 50 60 70 Frequency, (Hz) Figure A10. TCA wing spectral analysis of axial force, primary correction.

Model 6, Run 176 -- 60 '_ 0 c E 0 -60 c -120 ,m

....... No correction

o -180 IX -- Primary correction ! ! = -24O 0 2 4 6 Time (sec) Figure A11. TCA wing inertial loads correction for pitching moment.

e', ,4,' 2_ IX e- E o -0 e- c- o y = 2.299x - 1.9777 IX R2= 0.9941 Pitch Acceleration, (rad/sec 2) Figure A12. Correlation between pitching moment and pitch acceleration.

Pitch Acceleration

¢,1 ¢J ¢J 0 ¢J I I I I I I I -2 0 10 20 30 40 50 59 69 Frequency, (Hz) Figure A13. TCA wing spectral analysis of pitch acceleration.

Pitching Moment

" 6 e- E O e- ,_o -2 13.

0 10 20 30 40 50 59 69 Frequency, (Hz) Figure A14. TCA wing spectral analysis of pitching moment, no correction.

Corrected Pitching Moment

i ' '

_2 i i i i i i i

13.

0 10 20 30 40 50 59 69 Frequency, (Hz) Figure A15. TCA wing spectral analysis of pitching moment, primary correction.

Model 7,Run 149 ], Q d 40 .: ::::: _ ::- ::-.'.

,',: .;:,, _,; ', _ '.; _, IJ. L, ,, ,, , I ) , 0. _, '' "l ''|H'lll ''' I,:'m I _tm,r " ,_ /l_ , X, ilPIl'l",,""',,,*","'. ,,'_'\,""",,_,'_2_''_ _7''''_ _" ,m ,,, , . l, ,. ,,,, ._ _. 11.".'.',.'° ..' .... . '..' ,,. J, -" . " ,,, ,, ,m,,h b_ ,,,, ,,,I ,I ,m,. m .i i ", ,F,,,, ....... , %, ,,,%_=, Z -40 _"-_: ;, _.,, ....... No correchon ! ' --Primary correction -80 0 2 4 6 Time (sec) Figure A16. TU-144 wing inertial loads correction for normal force.

e'l • 5 i o" O o I,K i E o Z t5 y = 2.1463x - 0.0981 R 2 = 0.9976 -20 Normal Acceleration, (ft/sec _) Figure A17. TU-144 wing correlation between normal force and normal acceleration.

4O

NORMAL ACCELERATION

u v u u -2 0 10 20 30 40 50 60 70 Frequency, (Hz) Figure A18. TU-144 wing spectral analysis of normal acceleration.

NORMAL FORCE

m v .u O m

.E

O -4 Z 0 10 20 30 40 50 60 70 Frequency, (Hz) Figure A19. TU-144 wing spectral analysis of normal force, no correction.

CORRECTED NORMAL FORCE

• _ 12 m v G 8 .u O 4 14.

m o= 0 m

.E

O -4 • I I I I I I I Z 0 10 20 30 40 50 60 70 Frequency, (Hz) Figure A20. TU-144 wing spectral analysis of normal force, primary correction.

,, ,, Model 7, Run 149 I e'l i t_ L_ o ii i .i x -10 I: ....... No correction -- Primary correction -20 0 2 4 6 Time (sec) Figure A21. TU-144 wing inertial loads correction for axial force.

e'l i t_ x_ o | | ii 5 8 i x y = 1.4072x + 0.0255 R2= 0.9819 Axial Acceleration, (ft/sec 2) Figure A22. Correlation between axial force and axial acceleration.

AXIAL ACCELERATION

_, 2 tj 1.5 '*-' 1 :" 0.5 o 0 u "_ -0.5 0 10 20 30 40 50 60 70 Frequency, (Hz) Figure A23. TU-144 wing spectral analysis of axial acceleration.

AXIAL FORCE

.Q _" 1.5 =,9. 1 0 0.5 ^ m .m 0 x ,,_ -0.5 0 10 20 30 40 50 6O 7O Frequency, (Hz) Figure A24. TU-144 wing spectral analysis of axial force, no correction.

CORRECTED AXIAL FORCE

.Q m 1.5 .u 1 o 0.5 u.

o .,_ I I I I I I I ,,_ -0.5 0 10 20 30 40 50 60 70 Frequency, (Hz) Figure A25. TU-144 wing spectral analysis of axial force, primary correction.

Model 7, Run 149 ,,Q 120 m [ | 6O ° _J° : C E O -60 C .m -120 ..C O -180 IX -- Primary correction ! ! !

-240 2 4 6 Time (sec) Figure A26. TU-144 wing inertial loads correction for pitching moment.

e', m 10- _' 5- 15 • A_* _ _f_

Eo

I I I I _¢_, -5 • _i:: IX R 2 = 0.9912 ,t-5_ Pitch Acceleration, (rad/sec 2) Figure A27. TU-144 wing correlation between pitching moment and pitch acceleration.

Pitch Acceleration

tj "o v tj tj -1 0 10 20 30 40 50 59 69 Frequency, (Hz) Figure A28 Spectral Analysis of Pitch Acceleration.

Pitching Moment

..Q m

&

t-" E O e-" ,._o 13. -1 0 10 20 30 40 50 59 69 Frequency, (Hz) Figure A29 Spectral Analysis of Pitching Moment, no correction.

Corrected Pitching Moment

_' 4 t-" E o 1 -= 0 o. -1 I I I I I I I 0 10 20 30 40 50 59 69 Frequency, (Hz) Figure A30 Spectral Analysis of Pitching Moment, primary correction.

Model 10, Run 20 i %i ,, ,i . _' o _% ,_ ,P i ', _ f h, _, ,I '. ,. .I ,\ ,, ,, ,'. _i ,. ,I i, ., ,I , :. _' ', ;, .. ,' *, . • o I-- o ..... , ,, _ ,, , ,:, . ,', : ,,1 ,'. ', ,.,, ,: .';. ,, _, ,: ,, ,, ,, , , I,.I. 0 i , . ,, ,, . ,, i: ',: : c_ E ._ ...... ...........

I-- .; , ,. ,, ,: ,, ,, ,o .. . , o -10 '.' _ ,. ,, I; Z

l ....... Nocorrection

/ -- Primary correction / I i I -20 40 50 60 70 Time (sec) Figure A31. Elliptical wing inertial loads correction for normal force.

A i ii 5.

Z o" o !._ I I I o ii i E !._ o Z y = 4:7469x - 0:675 R2= 0.9962 Normal Acceleration, (ft/sec 2) Figure A32. Elliptical wing correlation between normal force and normal acceleration.

Normal Acceleration

_" 8 u

== 6

_. 4 v

8 0

u I I I I i I I '==: -2 10 20 30 40 50 60 70 Frequency, (Hz) Figure A33. Elliptical wing spectral analysis of normal acceleration.

Normal Force

__" 8 v .u 4 O i 2 -2 0 10 20 30 40 50 60 70 Frequency, (Hz) Figure A34. Elliptical wing spectral analysis of normal force, no correction.

Corrected Normal Force

G 6 .u 4 O u. 2 m A I I I I I I I -2 Z 0 10 20 30 40 50 60 70 Frequency, (Hz) Figure A35. Elliptical wing spectral analysis of normal force, primary correction.

15.0 Model 10, Run 20 ,,Q ,a i m 5.0 • .,;I.. ,, ',U" nil " I e" ", ,.'J :1 ,; _ . .

o I H I r • a _a , ,. _," ' v _ " _ t _ _ _, • _ i. , 0.0 o LI.

-5.0 X i I ,< -10.0 ....... No correction -- Primary correction -15.0 i i i , , 2.0 3.0 4.0 5.0 6.0 7.0

Time (see)

Figure A36. Elliptical wing inertial loads correction for axial force.

0:50 • e', m o" o x_ o ii ,m x ,< -2:O0 • y = 5.089x - 0:7388 R2 = 0.74 Axial Acceleration, (ft/sec 2) Figure A37. Elliptical wing correlation between axial force and axial acceleration.

Axial Acceleration

i 0.6 0.4

08! iii!

0 - -- - _.... _.... -- ---- 0.2 -0.2 Frequency, (Hz) Figure A38. Elliptical wing spectral analysis of axial acceleration.

Axial Force

_' 0.8 0.6 oe 0.4 0.2 '_ 0 -0.2 0 10 20 30 40 50 60 70 Frequency, (Hz) Figure A39. Elliptical wing spectral analysis of axial force, no correction.

Corrected Axial Force

0.6 oe 0.4 ,,o 0.2 __' 0.8 -- 0 _ -0.2 Frequency, (Hz) Figure A40. Elliptical wing spectral analysis of axial force, primary correction.

,,Q m i Mode i0 Run 20 '*- 60 c "l_lll?, _,_,,,, E _:_1 ,,,,,, , o 0 _._...,_ ,_ c .m ! '_ ""'1 _" "_"";;;'"" ,,c -60 o ....... No correction -- Primary correction I I I I I I I -120 1 2 3 4 5 6 7 Time (sec) Figure A41. Elliptical wing inertial loads correction for pitching moment.

e', e- 20 E I I I I I I o -60 -40 -2( 20 40 60 80 e- c- o a.

y = 1.0912x -0.371 R2= 0.9822 Pitch Acceleration, (rad/sec 2) Figure A42. Correlation between pitching moment and pitch acceleration.

Pitch Acceleration

u u_ 4 '10 • _ 2 v u I I i I I I I tj -2 0 10 20 30 40 50 60 70 Frequency, (Hz) Figure A43. Elliptical wing spectral analysis of pitch acceleration.

Pitching Moment

..Q m

&4

t-"

==2

O t'-" E-2 0 10 20 30 40 50 60 70 Frequency, (Hz) Figure A44. Elliptical wing spectral analysis of pitching moment, no correction.

Corrected Pitching Moment

t-" E O

o [

t'-" O 12.

0 10 20 30 40 50 60 70 Frequency, (Hz) Figure A45. Elliptical wing spectral analysis of pitching moment, primary correction.

APPENDIX B Post-Processing data using comboa

B.1 Logon Procedure Enter user id: dgetest Enter password: B.2 Setting up the Comboa Processing Directory Directory: export/home/dge Required input files: groups.pre groups. 1422 comboa inxxx answer Output files : logcomboa outcomboa euinfo windoff.log B.3 Defining the inxxx file csfile cs486 rpfile rpmame rawfile TEST46200229 229 -1 -1 YES NO NO PR ALL -1 B.3.1 rptname file The rptname file is used to specify the parameters to be processed for each run. A report is generated for theselected parameters andis called outcomboa.

B.4 Comboa user interface From cmdtool window: Type comboa Enter Operator Input File Name: inxxx STOP: Normal Termination of COMBOA!

APPENDIX C Post Processing data using dynamic The software package dynamic performs post processing of dynamic data collected from force- balance and accelerometer outputs. The program reads the most current answer data file created by comboa in the same directory. The following files are required for dynamic to function: accelr.F acceleration calculations and zero offset cal from run XXX dynam.F data reduction parameters such as lift and drag coefficients dynamic.F main processing unit ifind.F finds parameters in answer inertia.F performs a multivariate regression to calc moments of inertia mtgrt.F integrates accelerations to calculate velocities lpracc.F outputs accelerations lprbal.F output balance forces lprsig.F output signals lprvel.F output velocities linear.F performs mass calculations pm.F called by inertia, perfoms multivariate regression prload.F calculates aerodynamic loads readd.F reads answer rjusty.F right justifies search field rm.F 3-component multivariate regression rmld.F subroutine to filter the inertial loads out of the measurements setupd.F reads model configuration file config6.inp model 6 configuration file config7.inp model 7 configuration file configl0.inp model 8 configuration file groups.i params.i symfup.i Input File answer Output File naming convention -Accelerometer data from run Y runXXX_YYY_acc runXXX_YYY_dyn -Processed lift, drag coefficients, alpha, sink rate runXXX_YYY_lng -Longitudinal (Normal, Axial, and Pitch) loads and accelerations runXXX_YYY_ltd -Lateral (Roll, Yaw, and Side) loads and accelerations measured runXXX_YYY_ld -Velocities runXXX_YYY_vel -Balance data in voltage form as it was acquired runXXX_YYY_g -Accelerometer signals The subroutine first goes through a linear regression scheme of the three force equations to calculate the mass of the model. In these equations, m is the mass of everything on the model side of the strain gauge of the balance. The program then uses Multivariate regression to solve for the inertias and centroid positions involved in the three moment equations. The scheme used for solving for these constants was to solve for the most significant terms. Therefore, Iy (y- Inertia) in the pitching moment equation was calculated first, then Ix (x-Inertia) in the rolling moment equation and finally Iz (z-Inertia) in the yawing moment equation. The centroid positions were being calculated along with each of the inertias. The multivariate regression scheme has the following form: y= bl* xl + b2*x2 + b3*x3 where, bl, b2, b3 -regression constants (Inertias, centroid positions) xl, x2, x3 -independent variables (acceleration data arrays) -dependent variable (moment data arrays) Y Once the constants are calculated, they are used to subtract the inertial loads from the total loads in file runY.ld. The resulting residual loads are then formatted into a file which PREPLOT can easily read. The file is composed of two zones. The first zone is the total loads and the second is the residual loads.

Since the mass of the model, inertias and centroid positions are calculated with subroutine inertia, cards 5 and 6 in the configuration file (configY.inp) are not necessary. However, the distances, dist(i), from the accelerometers to the model's center of gravity will still need to be measured since they are used in the subroutine ACCELR.

C.1 Setting up the Dynamic Processing Directory Several model dependent configuration files are required in order to properly perform calculations: Model 6: config6.inp Model 7: config7.inp Model 10: configl0.inp Model configuration file The model configuration file (configxx.inp) contains the following information: x distance from balance moment reference center to six accelerometers (in inches) y distfince from balance moment reference center to six accelerometers (in inches) z distance from balance moment reference center to six accelerometers (in inches) accelerometer sensitivities (these were configured as -1.0 if the accelerometer was placed upside down) mass (slugs) as calculated by the calibration runs for each model Moments of inertia as calculated by the calibration runs for each model. (slug-f() Wing Area (ft2) SAREA1, BSPAN1 (inches) and Reference chord length, CHORD1 (inches) Model 6 configuration file card 1 - x distance from balance to accel 2.264 2.264 3.264 14.736 15.736 16.436 card 2 y distance from balance to accel 5.5 0 0 0 0 0 card 3 z distance from balance to accel -2.638 -2.638 -2.375 -2.638 -2.375 -2.375 card 4 x,y,z distance from balance to cg 0 0 -2.5 card 5 accel sensitivities 1.0 1.0 -1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 card 6 mass (slugs) 1.132 1.759 1.8531 card 7 Ixx Iyy Izz Ixz slug-ft2 reference to mrc 0.6299 2.3319 2.6956 -0.001

card8 Sarea bspan chord

7.894 48.0 34.723

Model 7 configuration file Card 1 - x distance from balance to accel -2.00 -2.00 -3.00 15.00 16.00 16.25 card 2 y distance from balance to accel 5.5 0 0 0 0 0 card 3 z distance from balance to accel -2.638 -2.638 -2.375 -2.638 -2.375 -2.375 carrd 4 x,y,z distance from balance to cg 0 0 0 card 5 accel sensitivities 1.0 1.0 -1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 card 6 mass (slugs) 1.347 1.987 2.144 card 7 Ixx Iyy Izz Ixz slug-ft2 reference to mrc 1.133 2.968 3.658 -0.025 card 8 Sarea bspan chord 9.466 47.1 38.25 Model 10 configuration file card 1 - x distance from balance to accel 0 0 29.03 11.65 11.65 16.53 card 2 y distance from balance to accel 2.625 0 1.75 0 1.75 0

card3

zdistance frombalance toaccel (notapplicable)

-2.638 -2.638 -2.375 -2.638 -2.375 -2.375

card4

x,y,zdistance frombalance tocg

0 0 0

card5 accel sensitivities

1.0 1.0 -1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0

card6

mass (slugs)

1.347 1.987 2.144

card7

Ixx Iyy Izz Ixz slug-ft2 reference to mrc

1.133 2.968 3.658 -0.025

card8

Sarea bspan chord

6.448 80.62212.331

APPENDIX D Accelerometers Accelerometer sensitivity coefficients 0.1999 0.1998 0.2005 0.2014 0.1987 0.2003 0.1995 0.1997 0.19805 0.19933 0.19932 0.20171 0.20012 0.19939 0.19827 0.19918 7290A-10 +10g 0-500 +2V +0.20 Accelerometer Orientation References 1 Roskam, J., Airplane Design Part VIII: Airplane Cost Estimation: Design, Development, Manufacturing and Operating. RAEC, Ottawa, Kansas, 1990.

2 Pope, Alan, Rae, William H., Jr., Low-Speed Wind Tunnel Testing. Wiley- Interscience, USA, 1984.

3 Kemp, W. B., Lockwood, V.E., and Phillips, W. P. "Ground Effects Related to Landing of Airplanes with Low-Aspect Ratio Wings," NASA TN D-3583, October 1966.

4 Chang, Ray Chung, An Experimental Investigation of Dynamic Ground Effect.

University of Kansas, 1985, pp. 26.

5 Gentry, Garl L., Jr., Quinto, P. Frank, Gatlin, Gregory M., and Applin, Zachary T., The Langley 14- by 22- Foot Subsonic Tunnel: Description, Flow Characteristics, and Guide for Users, NASA Technical P5.Paper 3008, September, 1990.

6 Gainer, Thomas G., Hoffman, Sherwood, Summary of Transformation Equations and Equations of Motion Used in Free-Flight and Wind-Tunnel Data Reduction and Analysis. NASA SP-3070, 1972, p.25.

7 Gainer, Thomas G., Hoffman, Sherwood, Summary of Transformation Equations and Equations of Motion Used in Free Flight and Wind Turtle Data Reduction and Analysis.

NASA SP-3070, 1972, p. 57.

8 Hamming, R.W., Digital Filters, Prentice-Hall, Inc., Englewood Cliffs, New Jersey, 1983.

9 Baker, Paul A., Schweikhard, William G., and Young, William R., Flight Evaluation of Ground Effect on Several Low-Aspect Ratio Airplanes, NASA TN-D-6053, Oct 1970.

10 Lee, Pai-Hung, Lan, C. Edward, and Muirhead, Vincent U., An Experimental Investigation of Dynamic Ground Effect, NASA CR-4105, 1987.

11 Chang, Ray Chung and Muirhead, Vincent U., Effect of Sink Rate on Ground Effect of Low-Aspect Ratio Wings, J. of Aircraft, vol. 24, no. 3, Mar 1986, pp. 176-180.

12 Kemmerly, Guy T. and Panlson, J. W., Jr., Investigation of Moving-Model Technique for Measuring Ground Effects, NASA TM-4080, 1989.

13 Curry, Robert E., Moulton, Bryan J., and Kresse, John, An In-Flight Investigation of Ground Effect on a Forward-Swept Wing Airplane, NASA TM-101708, Sept. 1989.

14 Corda, Stephen, Stephenson, Mark T., Burcham, Frank W., and Curry, Robert E., Dynamic Ground Effects Flight Test of an F-15 Aircraft, NASA TM-4604, Sept. 1994.

15 van Dam, C.P., Vijgen, P.M.H.W., and Holmes, B.J., Wind Tunnel Investigation on the Effect of the Crescent Planform Shape on Drag, AIAA-90-0300, p. 12 16 Kemmerly, Guy T., Dynamic Ground Effect Measurements on the F-15 STOL and Maneuver Technology Demonstrator (S/MTD) Configuration. NASA TP 3000, 1987.

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1. AGENCY USE ONLY (Leave blank) 2. REPORT DATE 3. REPORT TYPE AND DATES COVERED August 1999 Contractor Report 4. TITLE AND SUBTITLE 5. FUNDING NUMBERS Investigation of a Technique for Measuring Dynamic Ground Effect in a Subsonic Wind Tunnel NCC1-24 537-07-51-02 6. AUTHOR(S) Sharon S. Graves 8. PERFORMING ORGANIZATION 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) REPORT NUMBER The George Washington University Joint Institute for Advancement of Flight Sciences Langley Research Center, Hampton, Virginia 23681-2199 10. SPONSORING/MONITORING 9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) AGENCY REPORT NUMBER National Aeronautics and Space Administration NASA/CR- 1999 -209544 NASA Langley Research Center Hampton, VA 23681-2199 11. SUPPLEMENTARY NOTES Graves: Graduate Research Scholar Assistatant, GW JIAFS. This research was conducted in partial satisfaction of the requirements for the degree of Master of Science with The George Washington University.

Langley Technical Monitor: Edgar G. Waggoner 12a. DISTRIBUTION/AVAILABILITY STATEMENT 12b. DISTRIBUTION CODE Unclassified-Unlimited Subject Category 02 Distribution: Nonstandard Availability: NASA CASI (301) 621-0390 13. ABSTRACT (Maximum 200 words) To better understand the ground effect encountered by slender wing supersonic transport aircraft, a test was conducted at NASA Langley Research Center's 14 x 22 foot Subsonic Wind Tunnel in October, 1997.

Emphasis was placed on improving the accuracy of the ground effect data by using a "dynamic" technique in which the model's vertical motion was varied automatically during wind-on testing. This report describes and evaluates different aspects of the dynamic method utilized for obtaining ground effect data in this test. The method for acquiring and processing time data from a dynamic ground effect wind tunnel test is outlined with details of the overall data acquisition system and software used for the data analysis. The removal of inertial loads due to sting motion and the support dynamics in the balance force and moment data measurements of the aerodynamic forces on the model is described. An evaluation of the results identifies problem areas providing recommendations for future experiments. Test results are validated by comparing test data for an elliptical wing planform with an Elliptical wing planform section with a NACA 0012 airfoil to results found in current literature. Major aerodynamic forces acting on the model in terms of lift curves for determining ground effect are presented. Comparisons of flight and wind tunnel data for the TU-144 are presented.

14. SUBJECT TERMS 15. NUMBER OF PAGES Dynamic Ground Effect; Subsonic Wind Tunnel Test; Data Acquisition System 16. PRICE CODE A04 17. SECURITY CLASSIFICATION 18. SECURITY CLASSIFICATION 19. SECURITY CLASSIFICATION 20. LIMITATION OF REPORT OF THIS PAGE OF ABSTRACT OF ABSTRACT Unclassified Unclassified Unclassified NSN 7540-01-280-5500 Standard Form 298 (Rev. 2-89) Prescribed by ANSI Std. Z-39-18 298-102