langley research center model deformation measurements at nasa wind tunnels using videogrammetry
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Langley Research Center
MODEL DEFORMATION MEASUREMENTS AT NASA WIND TUNNELS USING VIDEOGRAMMETRY
Langley Research Center
AEROELASTIC DEFORMATION MEASUREMENTS
STATE-OF-THE-ART
twist due to aero loads
main wing element
CURRENT CHALLENGES
• Components (high lift)
flap, gap, and overhang
• Dynamics: up to 1000 Hz
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WHAT IS VIDEOGRAMMETRY
• Photogrammetry + video image processing
• Extraction of 2D or 3D info from 2D image data
• 1 camera 3D rigid body or 2D deformation
(1D must be known for 2D deformation)
• 2 or more cameras 3D deformation
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VIDEOGRAMMETRIC TECHNIQUE(VMD)
• Optical targets• Single-camera photogrammetry
X, Z computed with Y known• video-rate CCD camera• Frame grabber• Auto target location or tracking• 3-step calibration procedure
2.5 m
NTF test section
Z
Y
Looking downstream (+X)
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RETROREFLECTIVE TARGETS
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POLISHED PAINT TARGETSNational Transonic Facility
POLISHED PAINT TECHNIQUE• 0.0005 inch (1/2 mil) thickness• Feathered edges (no abrupt steps) • 10 inch surface roughness• Precision templates
1 2 3 4
56 7
X
Z
Flow
Full-span
Semispan
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CALIBRATION
(1) image plane corrections (2) coordinate system
(3) Wind-off polars for angle and X,Z
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FACILITIES
• National Transonic Facility
• Transonic Dynamics Tunnel
• 16-Ft Transonic Wind Tunnel
• Unitary Plan Wind Tunnel
• Ames 12-Ft Pressure Tunnel
Deformation measurements made from subsonic tosupersonic - high lift, cruise, onset of buffet
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NATIONAL TRANSONIC FACILITY(NTF)
• Cryogenic• High Re high Q• Last 9 tests: deformation
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VECTOR DISPLACEMENTS
1 2 3 4
56 7
X
Z
Flow
-15 -10 -5 0 5 10-20
-15
-10
-5
0
5
0.1 inch
1 2 3 4 5
X, inch
Z, i
nch
-5
24
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CHANGE IN GAP AND OVERHANG DUE TOAERODYNAMIC LOADING
-5 0 5 10 15 20 25-0.01
-0.005
0
0.005
0.01
0.015
Alpha, deg
Gap
, inc
h
Q=63.5 Q=347.5
-5 0 5 10 15 20 25-0.01
-0.005
0
0.005
0.01
0.015
Alpha, deg
Ove
rhan
g, in
ch
Q=63.5 Q=347.5
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DYNAMIC DEFORMATION OF SEMISPAN MODEL
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5-2
0
2
ZSLP1055 AOA
time, sec
1,
deg
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5-2
0
2
time, sec
2,
deg
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5-2
0
2
time, sec
3,
deg
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5-2
0
2
time, sec
4,
deg
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5-2
0
2
time, sec
5,
deg
0 5 10 15 20 25 300
1
2
3
4
5x 10
4
Frequency, Hz
Pow
er
Outboard Row
f = 10.6 Hz
f = 0.2 Hz
0 5 10 15 20 25 300
50
100
150
Frequency, Hz
Pow
er
Inboard Row
f = 10.6 Hz
f = 0.2 Hz
Time, sec
deg
Power
Power
f, Hz
Inboardf = 10.6 Hz
Outboardf = 10.6 Hz
Transonic Dynamics Tunnel
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X Y
Z
1
0.8
0.6
0.4
0.2
0
-0.2
-0.4
-0.6
-0.8
-1
DEFORMATION CONTOURS Z, inch
= 1= 0
0.000
0.017
0.034
0.050
0.067
t, sec
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MICRO AIR VEHICLEDEFORMATION CONTOURS
0.08
0.06
0.04
0.02
0
-0.02
-0.04
-0.06
-0.08
Z, inch
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867 FRAMES/SEC DATA ACQUIREDBASIC AERODYNAMIC RESEARCH TUNNEL
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CONCLUDING REMARKS
• Videogrammetry useful for static and dynamic aeroelastic measurements in wind tunnels
• Single-camera, single-view technique is workhorse• Useful for a number of tests at NASA facilities
– National Transonic Facility (last 9 customer tests)
– 16-Ft Transonic Wind Tunnel
– Transonic Dynamics Tunnel
– Unitary Plan Wind Tunnel
– Ames 12-Ft Pressure Tunnel
• Future efforts– Dynamic measurements up to 1000 Hz
– Micro air vehicles
– Ultralight and inflatable large space structures
– Robustness with and without targets