model deformation measurements at nasa wind tunnels using videogrammetry

Langley Research Center

MODEL DEFORMATION MEASUREMENTS AT NASA WIND TUNNELS USING VIDEOGRAMMETRY


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


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


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)


RETROREFLECTIVE TARGETS


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


CALIBRATION

(1) image plane corrections (2) coordinate system

(3) Wind-off polars for angle and X,Z


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


NATIONAL TRANSONIC FACILITY(NTF)

• Cryogenic• High Re high Q• Last 9 tests: deformation


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


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


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


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


MICRO AIR VEHICLEDEFORMATION CONTOURS

0.08

0.06

0.04

0.02

0

-0.02

-0.04

-0.06

-0.08

Z, inch


867 FRAMES/SEC DATA ACQUIREDBASIC AERODYNAMIC RESEARCH TUNNEL


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

model deformation measurements at nasa wind tunnels using videogrammetry

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