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Explore the state-of-the-art videogrammetry technique used for aeroelastic deformation measurements in NASA wind tunnels, including components, dynamics up to 1000 Hz, video processing, calibration, facilities, and future applications. See the latest advancements and challenges faced in aerodynamics research.
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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
2.5 m VIDEOGRAMMETRIC TECHNIQUE(VMD) NTF test section • 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 Looking downstream (+X) Z Y
1 2 3 4 5 6 7 Z Flow X POLISHED PAINT TARGETSNational Transonic Facility Semispan POLISHED PAINT TECHNIQUE • 0.0005 inch (1/2 mil) thickness • Feathered edges (no abrupt steps) • 10 inch surface roughness • Precision templates Full-span
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 to supersonic - high lift, cruise, onset of buffet
NATIONAL TRANSONIC FACILITY(NTF) • Cryogenic • High Re high Q • Last 9 tests: deformation
-5 1 2 3 4 5 6 7 Z 24 Flow X VECTOR DISPLACEMENTS
DYNAMIC DEFORMATION OF SEMISPAN MODEL Transonic Dynamics Tunnel Dq, deg Time, sec Inboard f = 10.6 Hz Power Outboard f = 10.6 Hz Power f, Hz
DEFORMATION CONTOURS DZ, inch h = 1 h = 0 D t, sec 0.000 0.017 0.034 0.050 0.067
DZ, inch 0 . 0 8 0 . 0 6 0 . 0 4 0 . 0 2 0 - 0 . 0 2 - 0 . 0 4 - 0 . 0 6 - 0 . 0 8 MICRO AIR VEHICLEDEFORMATION CONTOURS
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