Fundamental Aeronautics Program - NASA · • 4-Mega-pixel, 12-bit CCD progressive scan digital...

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National Aeronautics and Space Administration

www.nasa.gov

Fundamental Aeronautics Program!

2012 Technical Conference March 13-15, 2012

Anita Abrego Aerospace Engineer Aeromechanics/ Ames Research Center

Danny Barrows, Alpheus Burner, Larry Olson, Harriett Dismond, Eduardo Solis, Larry Meyn, Ethan Romander

Subsonic Rotary Wing Project!Status of Blade Displacement Measurements & Analysis

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Outline!

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•  Blade Displacement Measurements"•  Data Reduction and Validation"•  Future Considerations"•  Closing Remarks"

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Blade Displacement Measurements !

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Setup/Hardware"•  8-cameras, 2 per rotor quadrant"•  4-Mega-pixel, 12-bit CCD progressive scan

digital cameras, with a pixel resolution of 2048 × 2048 pixels "

•  Nikon 10.5 mm f/2.8 DX (fish-eye) lenses "•  Xenon flash-lamp 50 mJ strobes"

Blades"•  Targets on the lower surface of each blade"•  48 retro-reflective targets, 2 inch dia."•  3 per radial station at r/R from 0.2 to 0.97"

Ceiling"•  84 retro-reflective targets, 6 inch dia."•  84 coded targets"

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Blade Displacement Measurements!

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Primary! Secondary!Blades per quadrant" 4" 1"

Azimuth positions" 40" 11"Images per camera" 60" 12"

Total acquisition time" 10 min" 1 min"

Primary data conditions!•  27 primary data conditions"•  Includes cases with all Airloads data types"•  Matched conditions with PIV and RBOS data"•  Most images have been processed"•  Centroid inspections continue"Secondary data conditions!•  Most Airloads data points"•  Image processing is underway"

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Long-exposure (~10ms) view of quadrant-1 from BD data camera 2

10 µ-sec data shot exposures

Data Reduction and Validation!

Camera Intersection Example Synchronously Captured Images for Cameras 1, 2, 7, 8

Blade 1, ψ = 0°

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Camera Calibration Optimization •  Currently under investigation •  Static test data, 0° shaft angle, 40

azimuth positions and 3 images/azimuth •  Optimized the 3 camera position

coordinates and 3 angles of each camera


Baseline Optimized

ψ = 120° and r/R = 0.85

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Static Precision and Bias •  Static, wind-off measurements over 360° •  0° shaft angle •  40 azimuth positions,160 data points, 3 images each •  Mean of 160 determinations of the standard deviation at a single azimuth was used to

compute precision •  Bias error was computed as the standard deviation of the 160 samples over 360° after

removing the mean values of each blade

Data Reduction and Validation – Uncertainty Considerations!

r/R! Precision! Bias!Pitch" 0.007°" 0.267°"Flap" 0.007°" 0.372°"Lag" 0.002°" 0.366°"

Z"0.20" 0.002 in" 0.432 in"0.97" 0.066 in" 1.429 in"

Elastic Z"0.20" 0.002 in" 0.098 in"0.97" 0.038 in" 1.122 in"

Elastic Twist"0.20" 0.012°" 0.200°"0.97" 0.025°" 0.229°"

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Mean bias offset error •  Static, wind-off measurements over 360° •  40 azimuth positions •  160 data points, 3 images each •  0° shaft angle •  Collective pitch set to 0° •  Lag angle and elastic twist are expected to be near 0° •  Mean offset from 0 can be viewed as a bias offset error.

Data Reduction and Validation – Uncertainty Considerations!

r/R! Bias!Pitch" 0.97" 0.102°"Lag" 0.97" 2.253°"

Elastic Twist" 0.97" -0.023°"

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Bias Error vs Reference Transformation End r/R µ = 0.30, CT/σ = 0.10, Mtip = 0.65


0 0.2 0.4 0.6 0.8 12

1.5

1

0.5

0

0.5

1

1.5

2

Reference transformation end, r/R

Pitc

h, d

eg

tip bending 6 intip bending 0 intip bending 17 in

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 14

3

2

1

0

1

2

3


Flap

, deg


0 0.2 0.4 0.6 0.8 11

0.8

0.6

0.4

0.2

0

0.2

0.4

0.6

0.8

1


Lag,

deg


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Bias Error vs Reference Transformation End r/R µ = 0.30, CT/σ = 0.10, Mtip = 0.65


0 0.2 0.4 0.6 0.8 110

5

0

5

10

15

20


Elas

ticZ,

inch


0 0.2 0.4 0.6 0.8 10.5

0

0.5

1

Reference transformation end, r/REl

astic

twis

t, de

g


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Pitch, Flap and Lag with NFAC measured and CFD µ = 0.30, CT/σ = 0.10, Mtip = 0.65


0 30 60 90 120 150 180 210 240 270 300 330 3600

2

4

6

8

10

12

14

16

Azimuth, deg

pitc

h An

gle,

deg

Blade 1Blade 2Blade 3Blade 4CFD/CSDCommandedNFAC meas

0 30 60 90 120 150 180 210 240 270 300 330 3603

4

5

6

7

8

Azimuth, deg

Flap

Ang

le, d

eg

Blade 1Blade 2Blade 3Blade 4CFD/CSDNFAC meas

0 30 60 90 120 150 180 210 240 270 300 330 3601

2

3

4

5

6

7

8

9

Azimuth, deg

Lag

Angl

e, d

eg


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0 30 60 90 120 150 180 210 240 270 300 330 3600

2

4

6

8

10

12

14

16

Azimuth, deg

pitc

h An

gle,

deg

Blade 1Blade 2Blade 3Blade 4CFD/CSDCommandedNFAC meas

0 30 60 90 120 150 180 210 240 270 300 330 3604

3

2

1

0

1

2

3

Azimuth, deg

Pitc

h An

gle

Com

man

ded,

deg


Pitch vs Azimuth µ = 0.30, CT/σ = 0.10, Mtip = 0.65

Pitch − Commanded vs Azimuth µ = 0.30, CT/σ = 0.10, Mtip = 0.65

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0 30 60 90 120 150 180 210 240 270 300 330 3605

4

3

2

1

0

1

2

3

4

5

Azimuth, degEl

astic

Tw

ist,

deg

Blade 1Blade 2Blade 3Blade 4CFD/CSD

0 30 60 90 120 150 180 210 240 270 300 330 36020

15

10

5

0

5

10

Azimuth, deg

Elas

tic

Z, in

Blade 1Blade 2Blade 3Blade 4CFD/CSD

Elastic Bending and Elastic Twist with CFD µ = 0.30, CT/σ = 0.10, Mtip = 0.65, r/R = 0.97

Elastic Bending Elastic Twist

0 0.2 0.4 0.6 0.8 120

15

10

5

0

5

Radial position, r/R

Elas

tic

Z, in

ch

Measured, RBM EstimatedPredicted, RBM ExactPredicted, RBM Estimated

0 0.2 0.4 0.6 0.8 11

0

1

2

3

4

5

6

7


Elas

tic

Z, in

ch


0 0.2 0.4 0.6 0.8 11.5

1

0.5

0

0.5

1

1.5


Elas

tic

Z, in

ch


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Data Reduction and Validation!Elastic Bending with CFD

µ = 0.30, CT/σ = 0.10, Mtip = 0.65 ψ = 0° ψ = 150°

ψ = 255°

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Data Reduction and Validation!Elastic ΔZ Standard Deviation vs r/R

µ = 0.30, CT/σ = 0.10, Mtip = 0.65

ψ = 150° ψ = 0°

ψ = 255°

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Data Reduction and Validation!Change in ¼-chord Elastic Bending vs Revolution

µ = 0.30, CT/σ = 0.10, Mtip = 0.65

ψ = 0° ψ = 150°

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r/R = 0.20 r/R = 0.97 ψ = 255°

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Data Reduction and Validation!Elastic twist with CFD

µ = 0.30, CT/σ = 0.10, Mtip = 0.65

0 0.2 0.4 0.6 0.8 12

1.5

1

0.5

0

0.5

1


Elas

tic tw

ist,

deg

ExperimentExperiment meanComputed

0 0.2 0.4 0.6 0.8 15

4

3

2

1

0

1

2


Elas

tic tw

ist,

deg


0 0.2 0.4 0.6 0.8 13

2.5

2

1.5

1

0.5

0

0.5

1


Elas

tic tw

ist,

deg


ψ = 0° ψ = 150°

ψ = 255°

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Data Reduction and Validation!Elastic twist standard deviation vs r/R

µ = 0.30, CT/σ = 0.10, Mtip = 0.65 ψ = 0° ψ = 150°

ψ = 255°

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Data Reduction and Validation!Change in Elastic Twist vs Revolution

µ = 0.30, CT/σ = 0.10, Mtip = 0.65

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ψ = 0° ψ = 150°

ψ = 255°

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Future Work!

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Data Processing!•  Primary data point inspections"•  Secondary data point processing "•  Continue efforts to automate image processing and validation"•  Data processing and validation improvements continue,"

(1) optimization of camera calibrations"(2) alternate fish-eye corrections based on equisolid angle projection"(3) weighting of multiple intersection XYZ results by the variance to strengthen the final

intersection results "

Collaboration!•  Comparisons with computational results will continue and assist with data

validation"•  Comparisons with PIV and RBOS data"

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Closing Remarks !

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•  The static precision of the photogrammetry technique for pitch, flap, lag, were found from a static azimuth sweep to be less than 0.01°. "

•  Bias errors over the full range of azimuth can approach 0.4°. (All values are presented in terms of one standard deviation.) "

•  An additional mean bias offset error of 2.25° was discovered for lag angle for the static sweep. "

•  The static precision for elastic bending and twist were found to be 0.002 inch and 0.012° respectively, with bias errors over the full range of azimuth of 1.2 inch and 0.30° respectively."

•  Comparisons of experimental and computational results for a moderate advance ratio forward flight condition show good trend agreements, but show significant mean discrepancies for lag and elastic twist. "

•  The experimental values of pitch agree well with the NFAC DAS commanded pitch. "

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Closing Remarks!

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Preliminary results reported in the following publications,"–  Blade Displacement Measurements of the Full-Scale UH-60A Airloads

Rotor, American Institute of Aeronautics and Astronautics Applied Aerodynamics, June 2011."

–  Blade Displacement Measurement Technique Applied to a Full-Scale Rotor Test, American Helicopter Society 68th Annual Forum, May 2012."

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Fundamental Aeronautics Program - NASA · • 4-Mega-pixel, 12-bit CCD progressive scan digital...

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